[PATCH 13/13] drm/i915: Disable pipe gamma when C8 pixel format is used

[Ville Syrjala <ville.syrjala@linux.intel.com>]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Planes scanning out C8 will want to use the legacy lut as
their palette. That means the LUT content are unikely to
be useful for gamma correction on other planes. Thus we
should disable pipe gamma for all the other planes. And
we should reject any non legacy LUT configurations when
C8 planes are present.

Fixes the appearance of the hw cursor when running
X -depth 8.

Note that CHV with it's independent CGM degamma/gamma LUTs
could probably use the CGM for gamma correction even when
the legacy LUT is used for C8. But that would require a
new uapi for configuring the legacy LUT and CGM LUTs at
the same time. Totally not worth it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_atomic_plane.c | 5 +++++
 drivers/gpu/drm/i915/intel_color.c        | 8 +++++++-
 drivers/gpu/drm/i915/intel_drv.h          | 1 +
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_atomic_plane.c b/drivers/gpu/drm/i915/intel_atomic_plane.c
index 50be2c5dd76e..f311763867c4 100644
--- a/drivers/gpu/drm/i915/intel_atomic_plane.c
+++ b/drivers/gpu/drm/i915/intel_atomic_plane.c
@@ -119,6 +119,7 @@ int intel_plane_atomic_check_with_state(const struct intel_crtc_state *old_crtc_
 
 	new_crtc_state->active_planes &= ~BIT(plane->id);
 	new_crtc_state->nv12_planes &= ~BIT(plane->id);
+	new_crtc_state->c8_planes &= ~BIT(plane->id);
 	new_plane_state->base.visible = false;
 
 	if (!new_plane_state->base.crtc && !old_plane_state->base.crtc)
@@ -136,6 +137,10 @@ int intel_plane_atomic_check_with_state(const struct intel_crtc_state *old_crtc_
 	    new_plane_state->base.fb->format->format == DRM_FORMAT_NV12)
 		new_crtc_state->nv12_planes |= BIT(plane->id);
 
+	if (new_plane_state->base.visible &&
+	    new_plane_state->base.fb->format->format == DRM_FORMAT_C8)
+		new_crtc_state->c8_planes |= BIT(plane->id);
+
 	if (new_plane_state->base.visible || old_plane_state->base.visible)
 		new_crtc_state->update_planes |= BIT(plane->id);
 
diff --git a/drivers/gpu/drm/i915/intel_color.c b/drivers/gpu/drm/i915/intel_color.c
index 789b04bb51d2..c8d12653d77f 100644
--- a/drivers/gpu/drm/i915/intel_color.c
+++ b/drivers/gpu/drm/i915/intel_color.c
@@ -691,7 +691,13 @@ int intel_color_check(struct intel_crtc_state *crtc_state)
 	degamma_length = INTEL_INFO(dev_priv)->color.degamma_lut_size;
 	gamma_length = INTEL_INFO(dev_priv)->color.gamma_lut_size;
 
-	crtc_state->gamma_enable = gamma_lut || degamma_lut;
+	/* C8 needs the legacy LUT all to itself */
+	if (crtc_state->c8_planes &&
+	    !crtc_state_is_legacy_gamma(crtc_state))
+		return -EINVAL;
+
+	crtc_state->gamma_enable = (gamma_lut || degamma_lut) &&
+		!crtc_state->c8_planes;
 
 	if (INTEL_GEN(dev_priv) >= 9 ||
 	    IS_BROADWELL(dev_priv) || IS_HASWELL(dev_priv))
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index a4496f799af3..4d9ea05a6825 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -930,6 +930,7 @@ struct intel_crtc_state {
 	/* bitmask of visible planes (enum plane_id) */
 	u8 active_planes;
 	u8 nv12_planes;
+	u8 c8_planes;
 
 	/* bitmask of planes that will be updated during the commit */
 	u8 update_planes;
-- 
2.19.2

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