Merge tag 'drm-misc-next-2018-02-13' of git://anongit.freedesktop.org/drm/drm-misc into drm-next

drm-misc-next for 4.17: UAPI Changes: - drm/vc4: Expose performance counters to userspace (Boris) Cross-subsystem Changes: - MAINTAINERS: Linus to maintain panel-arm-versatile in -misc (Linus) Core Changes: - Only use swiotlb when necessary (Chunming) Driver Changes: - drm/panel: Add support for ARM Versatile panels (Linus) - pl111: Improvements around versatile panel support (Linus) ---------------------------------------- Tagged on 2018-02-06: drm-misc-next for 4.17: UAPI Changes: - Validate mode flags + type (Ville) - Deprecate unused mode flags PIXMUX, BCAST (Ville) - Deprecate unused mode types BUILTIN, CRTC_C, CLOCK_C, DEFAULT (Ville) Cross-subsystem Changes: - MAINTAINERS: s/Daniel/Maarten/ for drm-misc (Daniel) Core Changes: - gem: Export gem functions for drivers to use (Samuel) - bridge: Introduce bridge timings in drm_bridge (Linus) - dma-buf: Allow exclusive fence to be bundled in fence array when calling reservation_object_get_fences_rcu (Christian) - dp: Add training pattern 4 and HBR3 support to dp helpers (Manasi) - fourcc: Add alpha bit to formats to avoid driver format LUTs (Maxime) - mode: Various cleanups + add new device-wide .mode_valid hook (Ville) - atomic: Fix state leak when non-blocking commits fail (Leo) NOTE: IIRC, this was cross-picked to -fixes so it might fall out - crc: Allow polling on the data fd (Maarten) Driver Changes: - bridge/vga-dac: Add THS8134* support (Linus) - tinydrm: Various MIPI DBI improvements/cleanups (Noralf) - bridge/dw-mipi-dsi: Cleanups + use create_packet helper (Brian) - drm/sun4i: Add Display Engine frontend support (Maxime) - drm/sun4i: Add zpos support + increase num planes from 2 to 4 (Maxime) - various: Use drm_mode_get_hv_timing() to fill plane clip rectangle (Ville) - stm: Add 8-bit clut support, add dsi phy v1.31 support, +fixes (Phillipe) Cc: Boris Brezillon <boris.brezillon@free-electrons.com> Cc: Chunming Zhou <david1.zhou@amd.com> Cc: Samuel Li <Samuel.Li@amd.com> Cc: Linus Walleij <linus.walleij@linaro.org> Cc: Noralf Trønnes <noralf@tronnes.org> Cc: Brian Norris <briannorris@chromium.org> Cc: Maxime Ripard <maxime.ripard@free-electrons.com> Cc: Ville Syrjala <ville.syrjala@linux.intel.com> Cc: Christian König <christian.koenig@amd.com> Cc: Manasi Navare <manasi.d.navare@intel.com> Cc: Philippe Cornu <philippe.cornu@st.com> Cc: Leo (Sunpeng) Li <sunpeng.li@amd.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> * tag 'drm-misc-next-2018-02-13' of git://anongit.freedesktop.org/drm/drm-misc: (115 commits) drm/radeon: only enable swiotlb path when need v2 drm/amdgpu: only enable swiotlb alloc when need v2 drm: add func to get max iomem address v2 drm/vc4: Expose performance counters to userspace drm: Print the pid when debug logging an ioctl error. drm/stm: ltdc: remove non-alpha color formats on layer 2 for older hw drm/stm: ltdc: add non-alpha color formats drm/bridge/synopsys: dsi: Add 1.31 version support drm/bridge/synopsys: dsi: Add read feature drm/pl111: Support multiple endpoints on the CLCD drm/pl111: Support variants with broken VBLANK drm/pl111: Support variants with broken clock divider drm/pl111: Handle the Versatile RGB/BGR565 mode drm/pl111: Properly detect the ARM PL110 variants drm/panel: Add support for ARM Versatile panels drm/panel: Device tree bindings for ARM Versatile panels drm/bridge: Rename argument from crtc to bridge drm/crc: Add support for polling on the data fd. drm/sun4i: Use drm_mode_get_hv_timing() to populate plane clip rectangle drm/rcar-du: Use drm_mode_get_hv_timing() to populate plane clip rectangle ...
2018-02-16 09:29:27 +10:00
--- a/drivers/gpu/drm/sun4i/Makefile
+++ b/drivers/gpu/drm/sun4i/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 sun4i-backend-y			+= sun4i_backend.o sun4i_layer.o
+sun4i-frontend-y		+= sun4i_frontend.o

 sun4i-drm-y			+= sun4i_drv.o
 sun4i-drm-y			+= sun4i_framebuffer.o
@@ -24,6 +25,6 @@ obj-$(CONFIG_DRM_SUN4I)		+= sun4i-tcon.o
 obj-$(CONFIG_DRM_SUN4I)		+= sun4i_tv.o
 obj-$(CONFIG_DRM_SUN4I)		+= sun6i_drc.o

-obj-$(CONFIG_DRM_SUN4I_BACKEND)	+= sun4i-backend.o
+obj-$(CONFIG_DRM_SUN4I_BACKEND)	+= sun4i-backend.o sun4i-frontend.o
 obj-$(CONFIG_DRM_SUN4I_HDMI)	+= sun4i-drm-hdmi.o
 obj-$(CONFIG_DRM_SUN8I_MIXER)	+= sun8i-mixer.o
--- a/drivers/gpu/drm/sun4i/sun4i_backend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
@@ -11,6 +11,7 @@
 */

 #include <drm/drmP.h>
+#include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_crtc_helper.h>
@@ -26,6 +27,7 @@

 #include "sun4i_backend.h"
 #include "sun4i_drv.h"
+#include "sun4i_frontend.h"
 #include "sun4i_layer.h"
 #include "sunxi_engine.h"

@@ -93,7 +95,7 @@ void sun4i_backend_layer_enable(struct sun4i_backend *backend,
 static int sun4i_backend_drm_format_to_layer(struct drm_plane *plane,
 					     u32 format, u32 *mode)
 {
-	if ((plane->type == DRM_PLANE_TYPE_PRIMARY) &&
+	if (plane && (plane->type == DRM_PLANE_TYPE_PRIMARY) &&
 	    (format == DRM_FORMAT_ARGB8888))
 		format = DRM_FORMAT_XRGB8888;

@@ -141,7 +143,6 @@ int sun4i_backend_update_layer_coord(struct sun4i_backend *backend,
 				     int layer, struct drm_plane *plane)
 {
 	struct drm_plane_state *state = plane->state;
-	struct drm_framebuffer *fb = state->fb;

 	DRM_DEBUG_DRIVER("Updating layer %d\n", layer);

@@ -153,12 +154,6 @@ int sun4i_backend_update_layer_coord(struct sun4i_backend *backend,
 						   state->crtc_h));
 	}

-	/* Set the line width */
-	DRM_DEBUG_DRIVER("Layer line width: %d bits\n", fb->pitches[0] * 8);
-	regmap_write(backend->engine.regs,
-		     SUN4I_BACKEND_LAYLINEWIDTH_REG(layer),
-		     fb->pitches[0] * 8);
-
 	/* Set height and width */
 	DRM_DEBUG_DRIVER("Layer size W: %u H: %u\n",
 			 state->crtc_w, state->crtc_h);
@@ -210,6 +205,30 @@ int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
 	return 0;
 }

+int sun4i_backend_update_layer_frontend(struct sun4i_backend *backend,
+					int layer, uint32_t fmt)
+{
+	u32 val;
+	int ret;
+
+	ret = sun4i_backend_drm_format_to_layer(NULL, fmt, &val);
+	if (ret) {
+		DRM_DEBUG_DRIVER("Invalid format\n");
+		return ret;
+	}
+
+	regmap_update_bits(backend->engine.regs,
+			   SUN4I_BACKEND_ATTCTL_REG0(layer),
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN,
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN);
+
+	regmap_update_bits(backend->engine.regs,
+			   SUN4I_BACKEND_ATTCTL_REG1(layer),
+			   SUN4I_BACKEND_ATTCTL_REG1_LAY_FBFMT, val);
+
+	return 0;
+}
+
 int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
 				      int layer, struct drm_plane *plane)
 {
@@ -218,6 +237,12 @@ int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
 	u32 lo_paddr, hi_paddr;
 	dma_addr_t paddr;

+	/* Set the line width */
+	DRM_DEBUG_DRIVER("Layer line width: %d bits\n", fb->pitches[0] * 8);
+	regmap_write(backend->engine.regs,
+		     SUN4I_BACKEND_LAYLINEWIDTH_REG(layer),
+		     fb->pitches[0] * 8);
+
 	/* Get the start of the displayed memory */
 	paddr = drm_fb_cma_get_gem_addr(fb, state, 0);
 	DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &paddr);
@@ -246,6 +271,176 @@ int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
 	return 0;
 }

+int sun4i_backend_update_layer_zpos(struct sun4i_backend *backend, int layer,
+				    struct drm_plane *plane)
+{
+	struct drm_plane_state *state = plane->state;
+	unsigned int priority = state->normalized_zpos;
+
+	DRM_DEBUG_DRIVER("Setting layer %d's priority to %d\n", layer, priority);
+
+	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL_MASK,
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL(priority));
+
+	return 0;
+}
+
+static bool sun4i_backend_plane_uses_scaler(struct drm_plane_state *state)
+{
+	u16 src_h = state->src_h >> 16;
+	u16 src_w = state->src_w >> 16;
+
+	DRM_DEBUG_DRIVER("Input size %dx%d, output size %dx%d\n",
+			 src_w, src_h, state->crtc_w, state->crtc_h);
+
+	if ((state->crtc_h != src_h) || (state->crtc_w != src_w))
+		return true;
+
+	return false;
+}
+
+static bool sun4i_backend_plane_uses_frontend(struct drm_plane_state *state)
+{
+	struct sun4i_layer *layer = plane_to_sun4i_layer(state->plane);
+	struct sun4i_backend *backend = layer->backend;
+
+	if (IS_ERR(backend->frontend))
+		return false;
+
+	return sun4i_backend_plane_uses_scaler(state);
+}
+
+static void sun4i_backend_atomic_begin(struct sunxi_engine *engine,
+				       struct drm_crtc_state *old_state)
+{
+	u32 val;
+
+	WARN_ON(regmap_read_poll_timeout(engine->regs,
+					 SUN4I_BACKEND_REGBUFFCTL_REG,
+					 val, !(val & SUN4I_BACKEND_REGBUFFCTL_LOADCTL),
+					 100, 50000));
+}
+
+static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
+				      struct drm_crtc_state *crtc_state)
+{
+	struct drm_atomic_state *state = crtc_state->state;
+	struct drm_device *drm = state->dev;
+	struct drm_plane *plane;
+	unsigned int num_planes = 0;
+	unsigned int num_alpha_planes = 0;
+	unsigned int num_frontend_planes = 0;
+
+	DRM_DEBUG_DRIVER("Starting checking our planes\n");
+
+	if (!crtc_state->planes_changed)
+		return 0;
+
+	drm_for_each_plane_mask(plane, drm, crtc_state->plane_mask) {
+		struct drm_plane_state *plane_state =
+			drm_atomic_get_plane_state(state, plane);
+		struct sun4i_layer_state *layer_state =
+			state_to_sun4i_layer_state(plane_state);
+		struct drm_framebuffer *fb = plane_state->fb;
+		struct drm_format_name_buf format_name;
+
+		if (sun4i_backend_plane_uses_frontend(plane_state)) {
+			DRM_DEBUG_DRIVER("Using the frontend for plane %d\n",
+					 plane->index);
+
+			layer_state->uses_frontend = true;
+			num_frontend_planes++;
+		} else {
+			layer_state->uses_frontend = false;
+		}
+
+		DRM_DEBUG_DRIVER("Plane FB format is %s\n",
+				 drm_get_format_name(fb->format->format,
+						     &format_name));
+		if (fb->format->has_alpha)
+			num_alpha_planes++;
+
+		num_planes++;
+	}
+
+	/*
+	 * The hardware is a bit unusual here.
+	 *
+	 * Even though it supports 4 layers, it does the composition
+	 * in two separate steps.
+	 *
+	 * The first one is assigning a layer to one of its two
+	 * pipes. If more that 1 layer is assigned to the same pipe,
+	 * and if pixels overlaps, the pipe will take the pixel from
+	 * the layer with the highest priority.
+	 *
+	 * The second step is the actual alpha blending, that takes
+	 * the two pipes as input, and uses the eventual alpha
+	 * component to do the transparency between the two.
+	 *
+	 * This two steps scenario makes us unable to guarantee a
+	 * robust alpha blending between the 4 layers in all
+	 * situations, since this means that we need to have one layer
+	 * with alpha at the lowest position of our two pipes.
+	 *
+	 * However, we cannot even do that, since the hardware has a
+	 * bug where the lowest plane of the lowest pipe (pipe 0,
+	 * priority 0), if it has any alpha, will discard the pixel
+	 * entirely and just display the pixels in the background
+	 * color (black by default).
+	 *
+	 * This means that we effectively have only three valid
+	 * configurations with alpha, all of them with the alpha being
+	 * on pipe1 with the lowest position, which can be 1, 2 or 3
+	 * depending on the number of planes and their zpos.
+	 */
+	if (num_alpha_planes > SUN4I_BACKEND_NUM_ALPHA_LAYERS) {
+		DRM_DEBUG_DRIVER("Too many planes with alpha, rejecting...\n");
+		return -EINVAL;
+	}
+
+	if (num_frontend_planes > SUN4I_BACKEND_NUM_FRONTEND_LAYERS) {
+		DRM_DEBUG_DRIVER("Too many planes going through the frontend, rejecting\n");
+		return -EINVAL;
+	}
+
+	DRM_DEBUG_DRIVER("State valid with %u planes, %u alpha, %u video\n",
+			 num_planes, num_alpha_planes, num_frontend_planes);
+
+	return 0;
+}
+
+static void sun4i_backend_vblank_quirk(struct sunxi_engine *engine)
+{
+	struct sun4i_backend *backend = engine_to_sun4i_backend(engine);
+	struct sun4i_frontend *frontend = backend->frontend;
+
+	if (!frontend)
+		return;
+
+	/*
+	 * In a teardown scenario with the frontend involved, we have
+	 * to keep the frontend enabled until the next vblank, and
+	 * only then disable it.
+	 *
+	 * This is due to the fact that the backend will not take into
+	 * account the new configuration (with the plane that used to
+	 * be fed by the frontend now disabled) until we write to the
+	 * commit bit and the hardware fetches the new configuration
+	 * during the next vblank.
+	 *
+	 * So we keep the frontend around in order to prevent any
+	 * visual artifacts.
+	 */
+	spin_lock(&backend->frontend_lock);
+	if (backend->frontend_teardown) {
+		sun4i_frontend_exit(frontend);
+		backend->frontend_teardown = false;
+	}
+	spin_unlock(&backend->frontend_lock);
+};
+
 static int sun4i_backend_init_sat(struct device *dev) {
 	struct sun4i_backend *backend = dev_get_drvdata(dev);
 	int ret;
@@ -330,11 +525,43 @@ static int sun4i_backend_of_get_id(struct device_node *node)
 	return ret;
 }

+/* TODO: This needs to take multiple pipelines into account */
+static struct sun4i_frontend *sun4i_backend_find_frontend(struct sun4i_drv *drv,
+							  struct device_node *node)
+{
+	struct device_node *port, *ep, *remote;
+	struct sun4i_frontend *frontend;
+
+	port = of_graph_get_port_by_id(node, 0);
+	if (!port)
+		return ERR_PTR(-EINVAL);
+
+	for_each_available_child_of_node(port, ep) {
+		remote = of_graph_get_remote_port_parent(ep);
+		if (!remote)
+			continue;
+
+		/* does this node match any registered engines? */
+		list_for_each_entry(frontend, &drv->frontend_list, list) {
+			if (remote == frontend->node) {
+				of_node_put(remote);
+				of_node_put(port);
+				return frontend;
+			}
+		}
+	}
+
+	return ERR_PTR(-EINVAL);
+}
+
 static const struct sunxi_engine_ops sun4i_backend_engine_ops = {
+	.atomic_begin			= sun4i_backend_atomic_begin,
+	.atomic_check			= sun4i_backend_atomic_check,
 	.commit				= sun4i_backend_commit,
 	.layers_init			= sun4i_layers_init,
 	.apply_color_correction		= sun4i_backend_apply_color_correction,
 	.disable_color_correction	= sun4i_backend_disable_color_correction,
+	.vblank_quirk			= sun4i_backend_vblank_quirk,
 };

 static struct regmap_config sun4i_backend_regmap_config = {
@@ -360,6 +587,7 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
 	if (!backend)
 		return -ENOMEM;
 	dev_set_drvdata(dev, backend);
+	spin_lock_init(&backend->frontend_lock);

 	backend->engine.node = dev->of_node;
 	backend->engine.ops = &sun4i_backend_engine_ops;
@@ -367,6 +595,10 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
 	if (backend->engine.id < 0)
 		return backend->engine.id;

+	backend->frontend = sun4i_backend_find_frontend(drv, dev->of_node);
+	if (IS_ERR(backend->frontend))
+		dev_warn(dev, "Couldn't find matching frontend, frontend features disabled\n");
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	regs = devm_ioremap_resource(dev, res);
 	if (IS_ERR(regs))
--- a/drivers/gpu/drm/sun4i/sun4i_backend.h
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.h
@@ -72,6 +72,7 @@
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL(x)		((x) << 15)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL_MASK	GENMASK(11, 10)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL(x)			((x) << 10)
+#define SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN		BIT(1)

 #define SUN4I_BACKEND_ATTCTL_REG1(l)		(0x8a0 + (0x4 * (l)))
 #define SUN4I_BACKEND_ATTCTL_REG1_LAY_HSCAFCT		GENMASK(15, 14)
@@ -111,7 +112,9 @@
 #define SUN4I_BACKEND_SPRALPHACTL_REG		0x90c
 #define SUN4I_BACKEND_IYUVCTL_REG		0x920
 #define SUN4I_BACKEND_IYUVADD_REG(c)		(0x930 + (0x4 * (c)))
-#define SUN4I_BACKEND_IYUVLINEWITDTH_REG(c)	(0x940 + (0x4 * (c)))
+
+#define SUN4I_BACKEND_IYUVLINEWIDTH_REG(c)	(0x940 + (0x4 * (c)))
+
 #define SUN4I_BACKEND_YGCOEF_REG(c)		(0x950 + (0x4 * (c)))
 #define SUN4I_BACKEND_YGCONS_REG		0x95c
 #define SUN4I_BACKEND_URCOEF_REG(c)		(0x960 + (0x4 * (c)))
@@ -143,8 +146,13 @@
 #define SUN4I_BACKEND_HWCCOLORTAB_OFF		0x4c00
 #define SUN4I_BACKEND_PIPE_OFF(p)		(0x5000 + (0x400 * (p)))

+#define SUN4I_BACKEND_NUM_LAYERS		4
+#define SUN4I_BACKEND_NUM_ALPHA_LAYERS		1
+#define SUN4I_BACKEND_NUM_FRONTEND_LAYERS	1
+
 struct sun4i_backend {
 	struct sunxi_engine	engine;
+	struct sun4i_frontend	*frontend;

 	struct reset_control	*reset;

@@ -154,6 +162,10 @@ struct sun4i_backend {

 	struct clk		*sat_clk;
 	struct reset_control	*sat_reset;
+
+	/* Protects against races in the frontend teardown */
+	spinlock_t		frontend_lock;
+	bool			frontend_teardown;
 };

 static inline struct sun4i_backend *
@@ -170,5 +182,9 @@ int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
 				       int layer, struct drm_plane *plane);
 int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
 				      int layer, struct drm_plane *plane);
+int sun4i_backend_update_layer_frontend(struct sun4i_backend *backend,
+					int layer, uint32_t in_fmt);
+int sun4i_backend_update_layer_zpos(struct sun4i_backend *backend,
+				    int layer, struct drm_plane *plane);

 #endif /* _SUN4I_BACKEND_H_ */
--- a/drivers/gpu/drm/sun4i/sun4i_crtc.c
+++ b/drivers/gpu/drm/sun4i/sun4i_crtc.c
@@ -25,6 +25,7 @@

 #include <video/videomode.h>

+#include "sun4i_backend.h"
 #include "sun4i_crtc.h"
 #include "sun4i_drv.h"
 #include "sunxi_engine.h"
@@ -46,11 +47,25 @@ static struct drm_encoder *sun4i_crtc_get_encoder(struct drm_crtc *crtc)
 	return NULL;
 }

+static int sun4i_crtc_atomic_check(struct drm_crtc *crtc,
+				    struct drm_crtc_state *state)
+{
+	struct sun4i_crtc *scrtc = drm_crtc_to_sun4i_crtc(crtc);
+	struct sunxi_engine *engine = scrtc->engine;
+	int ret = 0;
+
+	if (engine && engine->ops && engine->ops->atomic_check)
+		ret = engine->ops->atomic_check(engine, state);
+
+	return ret;
+}
+
 static void sun4i_crtc_atomic_begin(struct drm_crtc *crtc,
 				    struct drm_crtc_state *old_state)
 {
 	struct sun4i_crtc *scrtc = drm_crtc_to_sun4i_crtc(crtc);
 	struct drm_device *dev = crtc->dev;
+	struct sunxi_engine *engine = scrtc->engine;
 	unsigned long flags;

 	if (crtc->state->event) {
@@ -60,7 +75,10 @@ static void sun4i_crtc_atomic_begin(struct drm_crtc *crtc,
 		scrtc->event = crtc->state->event;
 		spin_unlock_irqrestore(&dev->event_lock, flags);
 		crtc->state->event = NULL;
-	 }
+	}
+
+	if (engine->ops->atomic_begin)
+		engine->ops->atomic_begin(engine, old_state);
 }

 static void sun4i_crtc_atomic_flush(struct drm_crtc *crtc,
@@ -125,6 +143,7 @@ static void sun4i_crtc_mode_set_nofb(struct drm_crtc *crtc)
 }

 static const struct drm_crtc_helper_funcs sun4i_crtc_helper_funcs = {
+	.atomic_check	= sun4i_crtc_atomic_check,
 	.atomic_begin	= sun4i_crtc_atomic_begin,
 	.atomic_flush	= sun4i_crtc_atomic_flush,
 	.atomic_enable	= sun4i_crtc_atomic_enable,
--- a/drivers/gpu/drm/sun4i/sun4i_drv.c
+++ b/drivers/gpu/drm/sun4i/sun4i_drv.c
@@ -23,6 +23,7 @@
 #include <drm/drm_of.h>

 #include "sun4i_drv.h"
+#include "sun4i_frontend.h"
 #include "sun4i_framebuffer.h"
 #include "sun4i_tcon.h"

@@ -91,6 +92,7 @@ static int sun4i_drv_bind(struct device *dev)
 		goto free_drm;
 	}
 	drm->dev_private = drv;
+	INIT_LIST_HEAD(&drv->frontend_list);
 	INIT_LIST_HEAD(&drv->engine_list);
 	INIT_LIST_HEAD(&drv->tcon_list);

@@ -177,6 +179,14 @@ static bool sun4i_drv_node_is_frontend(struct device_node *node)
 		of_device_is_compatible(node, "allwinner,sun8i-a33-display-frontend");
 }

+static bool sun4i_drv_node_is_supported_frontend(struct device_node *node)
+{
+	if (IS_ENABLED(CONFIG_DRM_SUN4I_BACKEND))
+		return !!of_match_node(sun4i_frontend_of_table, node);
+
+	return false;
+}
+
 static bool sun4i_drv_node_is_tcon(struct device_node *node)
 {
 	return !!of_match_node(sun4i_tcon_of_table, node);
@@ -225,9 +235,11 @@ static int sun4i_drv_add_endpoints(struct device *dev,
 	int count = 0;

 	/*
-	 * We don't support the frontend for now, so we will never
-	 * have a device bound. Just skip over it, but we still want
-	 * the rest our pipeline to be added.
+	 * The frontend has been disabled in some of our old device
+	 * trees. If we find a node that is the frontend and is
+	 * disabled, we should just follow through and parse its
+	 * child, but without adding it to the component list.
+	 * Otherwise, we obviously want to add it to the list.
 	 */
 	if (!sun4i_drv_node_is_frontend(node) &&
 	    !of_device_is_available(node))
@@ -240,7 +252,14 @@ static int sun4i_drv_add_endpoints(struct device *dev,
 	if (sun4i_drv_node_is_connector(node))
 		return 0;

-	if (!sun4i_drv_node_is_frontend(node)) {
+	/*
+	 * If the device is either just a regular device, or an
+	 * enabled frontend supported by the driver, we add it to our
+	 * component list.
+	 */
+	if (!sun4i_drv_node_is_frontend(node) ||
+	    (sun4i_drv_node_is_supported_frontend(node) &&
+	     of_device_is_available(node))) {
 		/* Add current component */
 		DRM_DEBUG_DRIVER("Adding component %pOF\n", node);
 		drm_of_component_match_add(dev, match, compare_of, node);
--- a/drivers/gpu/drm/sun4i/sun4i_drv.h
+++ b/drivers/gpu/drm/sun4i/sun4i_drv.h
@@ -19,6 +19,7 @@

 struct sun4i_drv {
 	struct list_head	engine_list;
+	struct list_head	frontend_list;
 	struct list_head	tcon_list;
 };

--- a/drivers/gpu/drm/sun4i/sun4i_framebuffer.c
+++ b/drivers/gpu/drm/sun4i/sun4i_framebuffer.c
@@ -10,6 +10,7 @@
 * the License, or (at your option) any later version.
 */

+#include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_fb_cma_helper.h>
@@ -19,13 +20,33 @@
 #include "sun4i_drv.h"
 #include "sun4i_framebuffer.h"

+static int sun4i_de_atomic_check(struct drm_device *dev,
+				 struct drm_atomic_state *state)
+{
+	int ret;
+
+	ret = drm_atomic_helper_check_modeset(dev, state);
+	if (ret)
+		return ret;
+
+	ret = drm_atomic_normalize_zpos(dev, state);
+	if (ret)
+		return ret;
+
+	return drm_atomic_helper_check_planes(dev, state);
+}
+
 static const struct drm_mode_config_funcs sun4i_de_mode_config_funcs = {
 	.output_poll_changed	= drm_fb_helper_output_poll_changed,
-	.atomic_check		= drm_atomic_helper_check,
+	.atomic_check		= sun4i_de_atomic_check,
 	.atomic_commit		= drm_atomic_helper_commit,
 	.fb_create		= drm_gem_fb_create,
 };

+static struct drm_mode_config_helper_funcs sun4i_de_mode_config_helpers = {
+	.atomic_commit_tail	= drm_atomic_helper_commit_tail_rpm,
+};
+
 int sun4i_framebuffer_init(struct drm_device *drm)
 {
 	drm_mode_config_reset(drm);
@@ -34,6 +55,7 @@ int sun4i_framebuffer_init(struct drm_device *drm)
 	drm->mode_config.max_height = 8192;

 	drm->mode_config.funcs = &sun4i_de_mode_config_funcs;
+	drm->mode_config.helper_private = &sun4i_de_mode_config_helpers;

 	return drm_fb_cma_fbdev_init(drm, 32, 0);
 }
--- a/drivers/gpu/drm/sun4i/sun4i_frontend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_frontend.c
@@ -0,0 +1,389 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 Free Electrons
+ * Maxime Ripard <maxime.ripard@free-electrons.com>
+ */
+#include <drm/drmP.h>
+#include <drm/drm_gem_cma_helper.h>
+#include <drm/drm_fb_cma_helper.h>
+
+#include <linux/clk.h>
+#include <linux/component.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+
+#include "sun4i_drv.h"
+#include "sun4i_frontend.h"
+
+static const u32 sun4i_frontend_vert_coef[32] = {
+	0x00004000, 0x000140ff, 0x00033ffe, 0x00043ffd,
+	0x00063efc, 0xff083dfc, 0x000a3bfb, 0xff0d39fb,
+	0xff0f37fb, 0xff1136fa, 0xfe1433fb, 0xfe1631fb,
+	0xfd192ffb, 0xfd1c2cfb, 0xfd1f29fb, 0xfc2127fc,
+	0xfc2424fc, 0xfc2721fc, 0xfb291ffd, 0xfb2c1cfd,
+	0xfb2f19fd, 0xfb3116fe, 0xfb3314fe, 0xfa3611ff,
+	0xfb370fff, 0xfb390dff, 0xfb3b0a00, 0xfc3d08ff,
+	0xfc3e0600, 0xfd3f0400, 0xfe3f0300, 0xff400100,
+};
+
+static const u32 sun4i_frontend_horz_coef[64] = {
+	0x40000000, 0x00000000, 0x40fe0000, 0x0000ff03,
+	0x3ffd0000, 0x0000ff05, 0x3ffc0000, 0x0000ff06,
+	0x3efb0000, 0x0000ff08, 0x3dfb0000, 0x0000ff09,
+	0x3bfa0000, 0x0000fe0d, 0x39fa0000, 0x0000fe0f,
+	0x38fa0000, 0x0000fe10, 0x36fa0000, 0x0000fe12,
+	0x33fa0000, 0x0000fd16, 0x31fa0000, 0x0000fd18,
+	0x2ffa0000, 0x0000fd1a, 0x2cfa0000, 0x0000fc1e,
+	0x29fa0000, 0x0000fc21, 0x27fb0000, 0x0000fb23,
+	0x24fb0000, 0x0000fb26, 0x21fb0000, 0x0000fb29,
+	0x1ffc0000, 0x0000fa2b, 0x1cfc0000, 0x0000fa2e,
+	0x19fd0000, 0x0000fa30, 0x16fd0000, 0x0000fa33,
+	0x14fd0000, 0x0000fa35, 0x11fe0000, 0x0000fa37,
+	0x0ffe0000, 0x0000fa39, 0x0dfe0000, 0x0000fa3b,
+	0x0afe0000, 0x0000fa3e, 0x08ff0000, 0x0000fb3e,
+	0x06ff0000, 0x0000fb40, 0x05ff0000, 0x0000fc40,
+	0x03ff0000, 0x0000fd41, 0x01ff0000, 0x0000fe42,
+};
+
+static void sun4i_frontend_scaler_init(struct sun4i_frontend *frontend)
+{
+	int i;
+
+	for (i = 0; i < 32; i++) {
+		regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_HORZCOEF0_REG(i),
+			     sun4i_frontend_horz_coef[2 * i]);
+		regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_HORZCOEF0_REG(i),
+			     sun4i_frontend_horz_coef[2 * i]);
+		regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_HORZCOEF1_REG(i),
+			     sun4i_frontend_horz_coef[2 * i + 1]);
+		regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_HORZCOEF1_REG(i),
+			     sun4i_frontend_horz_coef[2 * i + 1]);
+		regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_VERTCOEF_REG(i),
+			     sun4i_frontend_vert_coef[i]);
+		regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_VERTCOEF_REG(i),
+			     sun4i_frontend_vert_coef[i]);
+	}
+
+	regmap_update_bits(frontend->regs, SUN4I_FRONTEND_FRM_CTRL_REG,
+			   SUN4I_FRONTEND_FRM_CTRL_COEF_ACCESS_CTRL,
+			   SUN4I_FRONTEND_FRM_CTRL_COEF_ACCESS_CTRL);
+}
+
+int sun4i_frontend_init(struct sun4i_frontend *frontend)
+{
+	return pm_runtime_get_sync(frontend->dev);
+}
+EXPORT_SYMBOL(sun4i_frontend_init);
+
+void sun4i_frontend_exit(struct sun4i_frontend *frontend)
+{
+	pm_runtime_put(frontend->dev);
+}
+EXPORT_SYMBOL(sun4i_frontend_exit);
+
+void sun4i_frontend_update_buffer(struct sun4i_frontend *frontend,
+				  struct drm_plane *plane)
+{
+	struct drm_plane_state *state = plane->state;
+	struct drm_framebuffer *fb = state->fb;
+	dma_addr_t paddr;
+
+	/* Set the line width */
+	DRM_DEBUG_DRIVER("Frontend stride: %d bytes\n", fb->pitches[0]);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_LINESTRD0_REG,
+		     fb->pitches[0]);
+
+	/* Set the physical address of the buffer in memory */
+	paddr = drm_fb_cma_get_gem_addr(fb, state, 0);
+	paddr -= PHYS_OFFSET;
+	DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &paddr);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_BUF_ADDR0_REG, paddr);
+}
+EXPORT_SYMBOL(sun4i_frontend_update_buffer);
+
+static int sun4i_frontend_drm_format_to_input_fmt(uint32_t fmt, u32 *val)
+{
+	switch (fmt) {
+	case DRM_FORMAT_ARGB8888:
+		*val = 5;
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int sun4i_frontend_drm_format_to_output_fmt(uint32_t fmt, u32 *val)
+{
+	switch (fmt) {
+	case DRM_FORMAT_XRGB8888:
+	case DRM_FORMAT_ARGB8888:
+		*val = 2;
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+int sun4i_frontend_update_formats(struct sun4i_frontend *frontend,
+				  struct drm_plane *plane, uint32_t out_fmt)
+{
+	struct drm_plane_state *state = plane->state;
+	struct drm_framebuffer *fb = state->fb;
+	u32 out_fmt_val;
+	u32 in_fmt_val;
+	int ret;
+
+	ret = sun4i_frontend_drm_format_to_input_fmt(fb->format->format,
+						     &in_fmt_val);
+	if (ret) {
+		DRM_DEBUG_DRIVER("Invalid input format\n");
+		return ret;
+	}
+
+	ret = sun4i_frontend_drm_format_to_output_fmt(out_fmt, &out_fmt_val);
+	if (ret) {
+		DRM_DEBUG_DRIVER("Invalid output format\n");
+		return ret;
+	}
+
+	/*
+	 * I have no idea what this does exactly, but it seems to be
+	 * related to the scaler FIR filter phase parameters.
+	 */
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_HORZPHASE_REG, 0x400);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_HORZPHASE_REG, 0x400);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_VERTPHASE0_REG, 0x400);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_VERTPHASE0_REG, 0x400);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_VERTPHASE1_REG, 0x400);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_VERTPHASE1_REG, 0x400);
+
+	regmap_write(frontend->regs, SUN4I_FRONTEND_INPUT_FMT_REG,
+		     SUN4I_FRONTEND_INPUT_FMT_DATA_MOD(1) |
+		     SUN4I_FRONTEND_INPUT_FMT_DATA_FMT(in_fmt_val) |
+		     SUN4I_FRONTEND_INPUT_FMT_PS(1));
+
+	/*
+	 * TODO: It look like the A31 and A80 at least will need the
+	 * bit 7 (ALPHA_EN) enabled when using a format with alpha (so
+	 * ARGB8888).
+	 */
+	regmap_write(frontend->regs, SUN4I_FRONTEND_OUTPUT_FMT_REG,
+		     SUN4I_FRONTEND_OUTPUT_FMT_DATA_FMT(out_fmt_val));
+
+	return 0;
+}
+EXPORT_SYMBOL(sun4i_frontend_update_formats);
+
+void sun4i_frontend_update_coord(struct sun4i_frontend *frontend,
+				 struct drm_plane *plane)
+{
+	struct drm_plane_state *state = plane->state;
+
+	/* Set height and width */
+	DRM_DEBUG_DRIVER("Frontend size W: %u H: %u\n",
+			 state->crtc_w, state->crtc_h);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_INSIZE_REG,
+		     SUN4I_FRONTEND_INSIZE(state->src_h >> 16,
+					   state->src_w >> 16));
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_INSIZE_REG,
+		     SUN4I_FRONTEND_INSIZE(state->src_h >> 16,
+					   state->src_w >> 16));
+
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_OUTSIZE_REG,
+		     SUN4I_FRONTEND_OUTSIZE(state->crtc_h, state->crtc_w));
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_OUTSIZE_REG,
+		     SUN4I_FRONTEND_OUTSIZE(state->crtc_h, state->crtc_w));
+
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_HORZFACT_REG,
+		     state->src_w / state->crtc_w);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_HORZFACT_REG,
+		     state->src_w / state->crtc_w);
+
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH0_VERTFACT_REG,
+		     state->src_h / state->crtc_h);
+	regmap_write(frontend->regs, SUN4I_FRONTEND_CH1_VERTFACT_REG,
+		     state->src_h / state->crtc_h);
+
+	regmap_write_bits(frontend->regs, SUN4I_FRONTEND_FRM_CTRL_REG,
+			  SUN4I_FRONTEND_FRM_CTRL_REG_RDY,
+			  SUN4I_FRONTEND_FRM_CTRL_REG_RDY);
+}
+EXPORT_SYMBOL(sun4i_frontend_update_coord);
+
+int sun4i_frontend_enable(struct sun4i_frontend *frontend)
+{
+	regmap_write_bits(frontend->regs, SUN4I_FRONTEND_FRM_CTRL_REG,
+			  SUN4I_FRONTEND_FRM_CTRL_FRM_START,
+			  SUN4I_FRONTEND_FRM_CTRL_FRM_START);
+
+	return 0;
+}
+EXPORT_SYMBOL(sun4i_frontend_enable);
+
+static struct regmap_config sun4i_frontend_regmap_config = {
+	.reg_bits	= 32,
+	.val_bits	= 32,
+	.reg_stride	= 4,
+	.max_register	= 0x0a14,
+};
+
+static int sun4i_frontend_bind(struct device *dev, struct device *master,
+			 void *data)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct sun4i_frontend *frontend;
+	struct drm_device *drm = data;
+	struct sun4i_drv *drv = drm->dev_private;
+	struct resource *res;
+	void __iomem *regs;
+
+	frontend = devm_kzalloc(dev, sizeof(*frontend), GFP_KERNEL);
+	if (!frontend)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, frontend);
+	frontend->dev = dev;
+	frontend->node = dev->of_node;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	regs = devm_ioremap_resource(dev, res);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	frontend->regs = devm_regmap_init_mmio(dev, regs,
+					       &sun4i_frontend_regmap_config);
+	if (IS_ERR(frontend->regs)) {
+		dev_err(dev, "Couldn't create the frontend regmap\n");
+		return PTR_ERR(frontend->regs);
+	}
+
+	frontend->reset = devm_reset_control_get(dev, NULL);
+	if (IS_ERR(frontend->reset)) {
+		dev_err(dev, "Couldn't get our reset line\n");
+		return PTR_ERR(frontend->reset);
+	}
+
+	frontend->bus_clk = devm_clk_get(dev, "ahb");
+	if (IS_ERR(frontend->bus_clk)) {
+		dev_err(dev, "Couldn't get our bus clock\n");
+		return PTR_ERR(frontend->bus_clk);
+	}
+
+	frontend->mod_clk = devm_clk_get(dev, "mod");
+	if (IS_ERR(frontend->mod_clk)) {
+		dev_err(dev, "Couldn't get our mod clock\n");
+		return PTR_ERR(frontend->mod_clk);
+	}
+
+	frontend->ram_clk = devm_clk_get(dev, "ram");
+	if (IS_ERR(frontend->ram_clk)) {
+		dev_err(dev, "Couldn't get our ram clock\n");
+		return PTR_ERR(frontend->ram_clk);
+	}
+
+	list_add_tail(&frontend->list, &drv->frontend_list);
+	pm_runtime_enable(dev);
+
+	return 0;
+}
+
+static void sun4i_frontend_unbind(struct device *dev, struct device *master,
+			    void *data)
+{
+	struct sun4i_frontend *frontend = dev_get_drvdata(dev);
+
+	list_del(&frontend->list);
+	pm_runtime_force_suspend(dev);
+}
+
+static const struct component_ops sun4i_frontend_ops = {
+	.bind	= sun4i_frontend_bind,
+	.unbind	= sun4i_frontend_unbind,
+};
+
+static int sun4i_frontend_probe(struct platform_device *pdev)
+{
+	return component_add(&pdev->dev, &sun4i_frontend_ops);
+}
+
+static int sun4i_frontend_remove(struct platform_device *pdev)
+{
+	component_del(&pdev->dev, &sun4i_frontend_ops);
+
+	return 0;
+}
+
+static int sun4i_frontend_runtime_resume(struct device *dev)
+{
+	struct sun4i_frontend *frontend = dev_get_drvdata(dev);
+	int ret;
+
+	clk_set_rate(frontend->mod_clk, 300000000);
+
+	clk_prepare_enable(frontend->bus_clk);
+	clk_prepare_enable(frontend->mod_clk);
+	clk_prepare_enable(frontend->ram_clk);
+
+	ret = reset_control_reset(frontend->reset);
+	if (ret) {
+		dev_err(dev, "Couldn't reset our device\n");
+		return ret;
+	}
+
+	regmap_update_bits(frontend->regs, SUN4I_FRONTEND_EN_REG,
+			   SUN4I_FRONTEND_EN_EN,
+			   SUN4I_FRONTEND_EN_EN);
+
+	regmap_update_bits(frontend->regs, SUN4I_FRONTEND_BYPASS_REG,
+			   SUN4I_FRONTEND_BYPASS_CSC_EN,
+			   SUN4I_FRONTEND_BYPASS_CSC_EN);
+
+	sun4i_frontend_scaler_init(frontend);
+
+	return 0;
+}
+
+static int sun4i_frontend_runtime_suspend(struct device *dev)
+{
+	struct sun4i_frontend *frontend = dev_get_drvdata(dev);
+
+	clk_disable_unprepare(frontend->ram_clk);
+	clk_disable_unprepare(frontend->mod_clk);
+	clk_disable_unprepare(frontend->bus_clk);
+
+	reset_control_assert(frontend->reset);
+
+	return 0;
+}
+
+static const struct dev_pm_ops sun4i_frontend_pm_ops = {
+	.runtime_resume		= sun4i_frontend_runtime_resume,
+	.runtime_suspend	= sun4i_frontend_runtime_suspend,
+};
+
+const struct of_device_id sun4i_frontend_of_table[] = {
+	{ .compatible = "allwinner,sun8i-a33-display-frontend" },
+	{ }
+};
+EXPORT_SYMBOL(sun4i_frontend_of_table);
+MODULE_DEVICE_TABLE(of, sun4i_frontend_of_table);
+
+static struct platform_driver sun4i_frontend_driver = {
+	.probe		= sun4i_frontend_probe,
+	.remove		= sun4i_frontend_remove,
+	.driver		= {
+		.name		= "sun4i-frontend",
+		.of_match_table	= sun4i_frontend_of_table,
+		.pm		= &sun4i_frontend_pm_ops,
+	},
+};
+module_platform_driver(sun4i_frontend_driver);
+
+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
+MODULE_DESCRIPTION("Allwinner A10 Display Engine Frontend Driver");
+MODULE_LICENSE("GPL");
--- a/drivers/gpu/drm/sun4i/sun4i_frontend.h
+++ b/drivers/gpu/drm/sun4i/sun4i_frontend.h
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 Free Electrons
+ * Maxime Ripard <maxime.ripard@free-electrons.com>
+ */
+
+#ifndef _SUN4I_FRONTEND_H_
+#define _SUN4I_FRONTEND_H_
+
+#include <linux/list.h>
+
+#define SUN4I_FRONTEND_EN_REG			0x000
+#define SUN4I_FRONTEND_EN_EN				BIT(0)
+
+#define SUN4I_FRONTEND_FRM_CTRL_REG		0x004
+#define SUN4I_FRONTEND_FRM_CTRL_COEF_ACCESS_CTRL	BIT(23)
+#define SUN4I_FRONTEND_FRM_CTRL_FRM_START		BIT(16)
+#define SUN4I_FRONTEND_FRM_CTRL_COEF_RDY		BIT(1)
+#define SUN4I_FRONTEND_FRM_CTRL_REG_RDY			BIT(0)
+
+#define SUN4I_FRONTEND_BYPASS_REG		0x008
+#define SUN4I_FRONTEND_BYPASS_CSC_EN			BIT(1)
+
+#define SUN4I_FRONTEND_BUF_ADDR0_REG		0x020
+
+#define SUN4I_FRONTEND_LINESTRD0_REG		0x040
+
+#define SUN4I_FRONTEND_INPUT_FMT_REG		0x04c
+#define SUN4I_FRONTEND_INPUT_FMT_DATA_MOD(mod)		((mod) << 8)
+#define SUN4I_FRONTEND_INPUT_FMT_DATA_FMT(fmt)		((fmt) << 4)
+#define SUN4I_FRONTEND_INPUT_FMT_PS(ps)			(ps)
+
+#define SUN4I_FRONTEND_OUTPUT_FMT_REG		0x05c
+#define SUN4I_FRONTEND_OUTPUT_FMT_DATA_FMT(fmt)		(fmt)
+
+#define SUN4I_FRONTEND_CH0_INSIZE_REG		0x100
+#define SUN4I_FRONTEND_INSIZE(h, w)			((((h) - 1) << 16) | (((w) - 1)))
+
+#define SUN4I_FRONTEND_CH0_OUTSIZE_REG		0x104
+#define SUN4I_FRONTEND_OUTSIZE(h, w)			((((h) - 1) << 16) | (((w) - 1)))
+
+#define SUN4I_FRONTEND_CH0_HORZFACT_REG		0x108
+#define SUN4I_FRONTEND_HORZFACT(i, f)			(((i) << 16) | (f))
+
+#define SUN4I_FRONTEND_CH0_VERTFACT_REG		0x10c
+#define SUN4I_FRONTEND_VERTFACT(i, f)			(((i) << 16) | (f))
+
+#define SUN4I_FRONTEND_CH0_HORZPHASE_REG	0x110
+#define SUN4I_FRONTEND_CH0_VERTPHASE0_REG	0x114
+#define SUN4I_FRONTEND_CH0_VERTPHASE1_REG	0x118
+
+#define SUN4I_FRONTEND_CH1_INSIZE_REG		0x200
+#define SUN4I_FRONTEND_CH1_OUTSIZE_REG		0x204
+#define SUN4I_FRONTEND_CH1_HORZFACT_REG		0x208
+#define SUN4I_FRONTEND_CH1_VERTFACT_REG		0x20c
+
+#define SUN4I_FRONTEND_CH1_HORZPHASE_REG	0x210
+#define SUN4I_FRONTEND_CH1_VERTPHASE0_REG	0x214
+#define SUN4I_FRONTEND_CH1_VERTPHASE1_REG	0x218
+
+#define SUN4I_FRONTEND_CH0_HORZCOEF0_REG(i)	(0x400 + i * 4)
+#define SUN4I_FRONTEND_CH0_HORZCOEF1_REG(i)	(0x480 + i * 4)
+#define SUN4I_FRONTEND_CH0_VERTCOEF_REG(i)	(0x500 + i * 4)
+#define SUN4I_FRONTEND_CH1_HORZCOEF0_REG(i)	(0x600 + i * 4)
+#define SUN4I_FRONTEND_CH1_HORZCOEF1_REG(i)	(0x680 + i * 4)
+#define SUN4I_FRONTEND_CH1_VERTCOEF_REG(i)	(0x700 + i * 4)
+
+struct clk;
+struct device_node;
+struct drm_plane;
+struct regmap;
+struct reset_control;
+
+struct sun4i_frontend {
+	struct list_head	list;
+	struct device		*dev;
+	struct device_node	*node;
+
+	struct clk		*bus_clk;
+	struct clk		*mod_clk;
+	struct clk		*ram_clk;
+	struct regmap		*regs;
+	struct reset_control	*reset;
+};
+
+extern const struct of_device_id sun4i_frontend_of_table[];
+
+int sun4i_frontend_init(struct sun4i_frontend *frontend);
+void sun4i_frontend_exit(struct sun4i_frontend *frontend);
+int sun4i_frontend_enable(struct sun4i_frontend *frontend);
+
+void sun4i_frontend_update_buffer(struct sun4i_frontend *frontend,
+				  struct drm_plane *plane);
+void sun4i_frontend_update_coord(struct sun4i_frontend *frontend,
+				 struct drm_plane *plane);
+int sun4i_frontend_update_formats(struct sun4i_frontend *frontend,
+				  struct drm_plane *plane, uint32_t out_fmt);
+
+#endif /* _SUN4I_FRONTEND_H_ */
--- a/drivers/gpu/drm/sun4i/sun4i_layer.c
+++ b/drivers/gpu/drm/sun4i/sun4i_layer.c
@@ -15,34 +15,107 @@
 #include <drm/drmP.h>

 #include "sun4i_backend.h"
+#include "sun4i_frontend.h"
 #include "sun4i_layer.h"
 #include "sunxi_engine.h"

 struct sun4i_plane_desc {
-	       enum drm_plane_type     type;
-	       u8                      pipe;
-	       const uint32_t          *formats;
-	       uint32_t                nformats;
+	enum drm_plane_type     type;
+	u8                      pipe;
+	const uint32_t          *formats;
+	uint32_t                nformats;
 };

+static void sun4i_backend_layer_reset(struct drm_plane *plane)
+{
+	struct sun4i_layer *layer = plane_to_sun4i_layer(plane);
+	struct sun4i_layer_state *state;
+
+	if (plane->state) {
+		state = state_to_sun4i_layer_state(plane->state);
+
+		__drm_atomic_helper_plane_destroy_state(&state->state);
+
+		kfree(state);
+		plane->state = NULL;
+	}
+
+	state = kzalloc(sizeof(*state), GFP_KERNEL);
+	if (state) {
+		plane->state = &state->state;
+		plane->state->plane = plane;
+		plane->state->zpos = layer->id;
+	}
+}
+
+static struct drm_plane_state *
+sun4i_backend_layer_duplicate_state(struct drm_plane *plane)
+{
+	struct sun4i_layer_state *orig = state_to_sun4i_layer_state(plane->state);
+	struct sun4i_layer_state *copy;
+
+	copy = kzalloc(sizeof(*copy), GFP_KERNEL);
+	if (!copy)
+		return NULL;
+
+	__drm_atomic_helper_plane_duplicate_state(plane, &copy->state);
+	copy->uses_frontend = orig->uses_frontend;
+
+	return &copy->state;
+}
+
+static void sun4i_backend_layer_destroy_state(struct drm_plane *plane,
+					      struct drm_plane_state *state)
+{
+	struct sun4i_layer_state *s_state = state_to_sun4i_layer_state(state);
+
+	__drm_atomic_helper_plane_destroy_state(state);
+
+	kfree(s_state);
+}
+
 static void sun4i_backend_layer_atomic_disable(struct drm_plane *plane,
 					       struct drm_plane_state *old_state)
 {
+	struct sun4i_layer_state *layer_state = state_to_sun4i_layer_state(old_state);
 	struct sun4i_layer *layer = plane_to_sun4i_layer(plane);
 	struct sun4i_backend *backend = layer->backend;

 	sun4i_backend_layer_enable(backend, layer->id, false);
+
+	if (layer_state->uses_frontend) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&backend->frontend_lock, flags);
+		backend->frontend_teardown = true;
+		spin_unlock_irqrestore(&backend->frontend_lock, flags);
+	}
 }

 static void sun4i_backend_layer_atomic_update(struct drm_plane *plane,
 					      struct drm_plane_state *old_state)
 {
+	struct sun4i_layer_state *layer_state = state_to_sun4i_layer_state(plane->state);
 	struct sun4i_layer *layer = plane_to_sun4i_layer(plane);
 	struct sun4i_backend *backend = layer->backend;
+	struct sun4i_frontend *frontend = backend->frontend;
+
+	if (layer_state->uses_frontend) {
+		sun4i_frontend_init(frontend);
+		sun4i_frontend_update_coord(frontend, plane);
+		sun4i_frontend_update_buffer(frontend, plane);
+		sun4i_frontend_update_formats(frontend, plane,
+					      DRM_FORMAT_ARGB8888);
+		sun4i_backend_update_layer_frontend(backend, layer->id,
+						    DRM_FORMAT_ARGB8888);
+		sun4i_frontend_enable(frontend);
+	} else {
+		sun4i_backend_update_layer_formats(backend, layer->id, plane);
+		sun4i_backend_update_layer_buffer(backend, layer->id, plane);
+	}

 	sun4i_backend_update_layer_coord(backend, layer->id, plane);
-	sun4i_backend_update_layer_formats(backend, layer->id, plane);
-	sun4i_backend_update_layer_buffer(backend, layer->id, plane);
+	sun4i_backend_update_layer_zpos(backend, layer->id, plane);
 	sun4i_backend_layer_enable(backend, layer->id, true);
 }

@@ -52,11 +125,11 @@ static const struct drm_plane_helper_funcs sun4i_backend_layer_helper_funcs = {
 };

 static const struct drm_plane_funcs sun4i_backend_layer_funcs = {
-	.atomic_destroy_state	= drm_atomic_helper_plane_destroy_state,
-	.atomic_duplicate_state	= drm_atomic_helper_plane_duplicate_state,
+	.atomic_destroy_state	= sun4i_backend_layer_destroy_state,
+	.atomic_duplicate_state	= sun4i_backend_layer_duplicate_state,
 	.destroy		= drm_plane_cleanup,
 	.disable_plane		= drm_atomic_helper_disable_plane,
-	.reset			= drm_atomic_helper_plane_reset,
+	.reset			= sun4i_backend_layer_reset,
 	.update_plane		= drm_atomic_helper_update_plane,
 };

@@ -128,32 +201,12 @@ struct drm_plane **sun4i_layers_init(struct drm_device *drm,
 	struct sun4i_backend *backend = engine_to_sun4i_backend(engine);
 	int i;

-	planes = devm_kcalloc(drm->dev, ARRAY_SIZE(sun4i_backend_planes) + 1,
+	/* We need to have a sentinel at the need, hence the overallocation */
+	planes = devm_kcalloc(drm->dev, SUN4I_BACKEND_NUM_LAYERS + 1,
 			      sizeof(*planes), GFP_KERNEL);
 	if (!planes)
 		return ERR_PTR(-ENOMEM);

-	/*
-	 * The hardware is a bit unusual here.
-	 *
-	 * Even though it supports 4 layers, it does the composition
-	 * in two separate steps.
-	 *
-	 * The first one is assigning a layer to one of its two
-	 * pipes. If more that 1 layer is assigned to the same pipe,
-	 * and if pixels overlaps, the pipe will take the pixel from
-	 * the layer with the highest priority.
-	 *
-	 * The second step is the actual alpha blending, that takes
-	 * the two pipes as input, and uses the eventual alpha
-	 * component to do the transparency between the two.
-	 *
-	 * This two steps scenario makes us unable to guarantee a
-	 * robust alpha blending between the 4 layers in all
-	 * situations. So we just expose two layers, one per pipe. On
-	 * SoCs that support it, sprites could fill the need for more
-	 * layers.
-	 */
 	for (i = 0; i < ARRAY_SIZE(sun4i_backend_planes); i++) {
 		const struct sun4i_plane_desc *plane = &sun4i_backend_planes[i];
 		struct sun4i_layer *layer;
@@ -165,6 +218,8 @@ struct drm_plane **sun4i_layers_init(struct drm_device *drm,
 			return ERR_CAST(layer);
 		};

+		drm_plane_create_zpos_immutable_property(&layer->plane, i);
+
 		DRM_DEBUG_DRIVER("Assigning %s plane to pipe %d\n",
 				 i ? "overlay" : "primary", plane->pipe);
 		regmap_update_bits(engine->regs, SUN4I_BACKEND_ATTCTL_REG0(i),
--- a/drivers/gpu/drm/sun4i/sun4i_layer.h
+++ b/drivers/gpu/drm/sun4i/sun4i_layer.h
@@ -22,12 +22,23 @@ struct sun4i_layer {
 	int			id;
 };

+struct sun4i_layer_state {
+	struct drm_plane_state	state;
+	bool			uses_frontend;
+};
+
 static inline struct sun4i_layer *
 plane_to_sun4i_layer(struct drm_plane *plane)
 {
 	return container_of(plane, struct sun4i_layer, plane);
 }

+static inline struct sun4i_layer_state *
+state_to_sun4i_layer_state(struct drm_plane_state *state)
+{
+	return container_of(state, struct sun4i_layer_state, state);
+}
+
 struct drm_plane **sun4i_layers_init(struct drm_device *drm,
 				     struct sunxi_engine *engine);

--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -540,6 +540,7 @@ static irqreturn_t sun4i_tcon_handler(int irq, void *private)
 	struct sun4i_tcon *tcon = private;
 	struct drm_device *drm = tcon->drm;
 	struct sun4i_crtc *scrtc = tcon->crtc;
+	struct sunxi_engine *engine = scrtc->engine;
 	unsigned int status;

 	regmap_read(tcon->regs, SUN4I_TCON_GINT0_REG, &status);
@@ -557,6 +558,9 @@ static irqreturn_t sun4i_tcon_handler(int irq, void *private)
 			   SUN4I_TCON_GINT0_VBLANK_INT(1),
 			   0);

+	if (engine->ops->vblank_quirk)
+		engine->ops->vblank_quirk(engine);
+
 	return IRQ_HANDLED;
 }

--- a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
@@ -211,7 +211,7 @@ static int sun8i_ui_layer_atomic_check(struct drm_plane *plane,
 	struct drm_crtc *crtc = state->crtc;
 	struct drm_crtc_state *crtc_state;
 	int min_scale, max_scale;
-	struct drm_rect clip;
+	struct drm_rect clip = {};

 	if (!crtc)
 		return 0;
@@ -220,10 +220,9 @@ static int sun8i_ui_layer_atomic_check(struct drm_plane *plane,
 	if (WARN_ON(!crtc_state))
 		return -EINVAL;

-	clip.x1 = 0;
-	clip.y1 = 0;
-	clip.x2 = crtc_state->adjusted_mode.hdisplay;
-	clip.y2 = crtc_state->adjusted_mode.vdisplay;
+	if (crtc_state->enable)
+		drm_mode_get_hv_timing(&crtc_state->mode,
+				       &clip.x2, &clip.y2);

 	min_scale = DRM_PLANE_HELPER_NO_SCALING;
 	max_scale = DRM_PLANE_HELPER_NO_SCALING;
--- a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
@@ -239,7 +239,7 @@ static int sun8i_vi_layer_atomic_check(struct drm_plane *plane,
 	struct drm_crtc *crtc = state->crtc;
 	struct drm_crtc_state *crtc_state;
 	int min_scale, max_scale;
-	struct drm_rect clip;
+	struct drm_rect clip = {};

 	if (!crtc)
 		return 0;
@@ -248,10 +248,9 @@ static int sun8i_vi_layer_atomic_check(struct drm_plane *plane,
 	if (WARN_ON(!crtc_state))
 		return -EINVAL;

-	clip.x1 = 0;
-	clip.y1 = 0;
-	clip.x2 = crtc_state->adjusted_mode.hdisplay;
-	clip.y2 = crtc_state->adjusted_mode.vdisplay;
+	if (crtc_state->enable)
+		drm_mode_get_hv_timing(&crtc_state->mode,
+				       &clip.x2, &clip.y2);

 	min_scale = DRM_PLANE_HELPER_NO_SCALING;
 	max_scale = DRM_PLANE_HELPER_NO_SCALING;
--- a/drivers/gpu/drm/sun4i/sunxi_engine.h
+++ b/drivers/gpu/drm/sun4i/sunxi_engine.h
@@ -12,16 +12,106 @@

 struct drm_plane;
 struct drm_device;
+struct drm_crtc_state;

 struct sunxi_engine;

+/**
+ * struct sunxi_engine_ops - helper operations for sunXi engines
+ *
+ * These hooks are used by the common part of the DRM driver to
+ * implement the proper behaviour.
+ */
 struct sunxi_engine_ops {
+	/**
+	 * @atomic_begin:
+	 *
+	 * This callback allows to prepare our engine for an atomic
+	 * update. This is mirroring the
+	 * &drm_crtc_helper_funcs.atomic_begin callback, so any
+	 * documentation there applies.
+	 *
+	 * This function is optional.
+	 */
+	void (*atomic_begin)(struct sunxi_engine *engine,
+			     struct drm_crtc_state *old_state);
+
+	/**
+	 * @atomic_check:
+	 *
+	 * This callback allows to validate plane-update related CRTC
+	 * constraints specific to engines. This is mirroring the
+	 * &drm_crtc_helper_funcs.atomic_check callback, so any
+	 * documentation there applies.
+	 *
+	 * This function is optional.
+	 *
+	 * RETURNS:
+	 *
+	 * 0 on success or a negative error code.
+	 */
+	int (*atomic_check)(struct sunxi_engine *engine,
+			    struct drm_crtc_state *state);
+
+	/**
+	 * @commit:
+	 *
+	 * This callback will trigger the hardware switch to commit
+	 * the new configuration that has been setup during the next
+	 * vblank period.
+	 *
+	 * This function is optional.
+	 */
 	void (*commit)(struct sunxi_engine *engine);
+
+	/**
+	 * @layers_init:
+	 *
+	 * This callback is used to allocate, initialize and register
+	 * the layers supported by that engine.
+	 *
+	 * This function is mandatory.
+	 *
+	 * RETURNS:
+	 *
+	 * The array of struct drm_plane backing the layers, or an
+	 * error pointer on failure.
+	 */
 	struct drm_plane **(*layers_init)(struct drm_device *drm,
 					  struct sunxi_engine *engine);

+	/**
+	 * @apply_color_correction:
+	 *
+	 * This callback will enable the color correction in the
+	 * engine. This is useful only for the composite output.
+	 *
+	 * This function is optional.
+	 */
 	void (*apply_color_correction)(struct sunxi_engine *engine);
+
+	/**
+	 * @disable_color_correction:
+	 *
+	 * This callback will stop the color correction in the
+	 * engine. This is useful only for the composite output.
+	 *
+	 * This function is optional.
+	 */
 	void (*disable_color_correction)(struct sunxi_engine *engine);
+
+	/**
+	 * @vblank_quirk:
+	 *
+	 * This callback is used to implement engine-specific
+	 * behaviour part of the VBLANK event. It is run with all the
+	 * constraints of an interrupt (can't sleep, all local
+	 * interrupts disabled) and therefore should be as fast as
+	 * possible.
+	 *
+	 * This function is optional.
+	 */
+	void (*vblank_quirk)(struct sunxi_engine *engine);
 };

 /**