drm/nouveau: disallow fbcon accel if running in interrupt context

A future commit will add locking to the DRM's channel, and there's numerous
problems that come up if we allow printk from an interrupt context to be
accelerated.  It seems saner to just disallow it completely.

As a nice side-effect, all the "to accel or not to accel" logic gets moved
out of the chipset-specific code.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nv04_fbcon.c

@@ -28,52 +28,39 @@
 #include "nouveau_ramht.h"
 #include "nouveau_fbcon.h"
 
-void
+int
 nv04_fbcon_copyarea(struct fb_info *info, const struct fb_copyarea *region)
 {
 	struct nouveau_fbdev *nfbdev = info->par;
 	struct drm_device *dev = nfbdev->dev;
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_channel *chan = dev_priv->channel;
+	int ret;
 
-	if (info->state != FBINFO_STATE_RUNNING)
-		return;
-
-	if (!(info->flags & FBINFO_HWACCEL_DISABLED) && RING_SPACE(chan, 4)) {
-		nouveau_fbcon_gpu_lockup(info);
-	}
-
-	if (info->flags & FBINFO_HWACCEL_DISABLED) {
-		cfb_copyarea(info, region);
-		return;
-	}
+	ret = RING_SPACE(chan, 4);
+	if (ret)
+		return ret;
 
 	BEGIN_RING(chan, NvSubImageBlit, 0x0300, 3);
 	OUT_RING(chan, (region->sy << 16) | region->sx);
 	OUT_RING(chan, (region->dy << 16) | region->dx);
 	OUT_RING(chan, (region->height << 16) | region->width);
 	FIRE_RING(chan);
+	return 0;
 }
 
-void
+int
 nv04_fbcon_fillrect(struct fb_info *info, const struct fb_fillrect *rect)
 {
 	struct nouveau_fbdev *nfbdev = info->par;
 	struct drm_device *dev = nfbdev->dev;
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_channel *chan = dev_priv->channel;
+	int ret;
 
-	if (info->state != FBINFO_STATE_RUNNING)
-		return;
-
-	if (!(info->flags & FBINFO_HWACCEL_DISABLED) && RING_SPACE(chan, 7)) {
-		nouveau_fbcon_gpu_lockup(info);
-	}
-
-	if (info->flags & FBINFO_HWACCEL_DISABLED) {
-		cfb_fillrect(info, rect);
-		return;
-	}
+	ret = RING_SPACE(chan, 7);
+	if (ret)
+		return ret;
 
 	BEGIN_RING(chan, NvSubGdiRect, 0x02fc, 1);
 	OUT_RING(chan, (rect->rop != ROP_COPY) ? 1 : 3);
@@ -87,9 +74,10 @@ nv04_fbcon_fillrect(struct fb_info *info, const struct fb_fillrect *rect)
 	OUT_RING(chan, (rect->dx << 16) | rect->dy);
 	OUT_RING(chan, (rect->width << 16) | rect->height);
 	FIRE_RING(chan);
+	return 0;
 }
 
-void
+int
 nv04_fbcon_imageblit(struct fb_info *info, const struct fb_image *image)
 {
 	struct nouveau_fbdev *nfbdev = info->par;
@@ -101,23 +89,14 @@ nv04_fbcon_imageblit(struct fb_info *info, const struct fb_image *image)
 	uint32_t dsize;
 	uint32_t width;
 	uint32_t *data = (uint32_t *)image->data;
+	int ret;
 
-	if (info->state != FBINFO_STATE_RUNNING)
-		return;
+	if (image->depth != 1)
+		return -ENODEV;
 
-	if (image->depth != 1) {
-		cfb_imageblit(info, image);
-		return;
-	}
-
-	if (!(info->flags & FBINFO_HWACCEL_DISABLED) && RING_SPACE(chan, 8)) {
-		nouveau_fbcon_gpu_lockup(info);
-	}
-
-	if (info->flags & FBINFO_HWACCEL_DISABLED) {
-		cfb_imageblit(info, image);
-		return;
-	}
+	ret = RING_SPACE(chan, 8);
+	if (ret)
+		return ret;
 
 	width = ALIGN(image->width, 8);
 	dsize = ALIGN(width * image->height, 32) >> 5;
@@ -144,11 +123,9 @@ nv04_fbcon_imageblit(struct fb_info *info, const struct fb_image *image)
 	while (dsize) {
 		int iter_len = dsize > 128 ? 128 : dsize;
 
-		if (RING_SPACE(chan, iter_len + 1)) {
-			nouveau_fbcon_gpu_lockup(info);
-			cfb_imageblit(info, image);
-			return;
-		}
+		ret = RING_SPACE(chan, iter_len + 1);
+		if (ret)
+			return ret;
 
 		BEGIN_RING(chan, NvSubGdiRect, 0x0c00, iter_len);
 		OUT_RINGp(chan, data, iter_len);
@@ -157,6 +134,7 @@ nv04_fbcon_imageblit(struct fb_info *info, const struct fb_image *image)
 	}
 
 	FIRE_RING(chan);
+	return 0;
 }
 
 static int