drm/vc4: Add CTM support

The hardware has a single block for applying a CTM prior to gamma lut.
It can be fed with pixels from one of our CRTC at a time and uses a
matrix with S0.9 scalars. Use private atomic state to reject attempts
from userland to apply CTM for more than one CRTC at a time and reject
matrices with scalars that we can't approximate without integer bits.

Signed-off-by: Stefan Schake <stschake@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/218067/

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -1018,6 +1018,11 @@ static int vc4_crtc_bind(struct device *dev, struct device *master, void *data)
 	drm_mode_crtc_set_gamma_size(crtc, ARRAY_SIZE(vc4_crtc->lut_r));
 	drm_crtc_enable_color_mgmt(crtc, 0, false, crtc->gamma_size);
 
+	/* We support CTM, but only for one CRTC at a time. It's therefore
+	 * implemented as private driver state in vc4_kms, not here.
+	 */
+	drm_crtc_enable_color_mgmt(crtc, 0, true, crtc->gamma_size);
+
 	/* Set up some arbitrary number of planes.  We're not limited
 	 * by a set number of physical registers, just the space in
 	 * the HVS (16k) and how small an plane can be (28 bytes).