[PATCH v2] drm/omap: Implement CTM property for CRTC using OVL managers CPR matrix

[Jyri Sarha]

Implement CTM color management property for OMAP CRTC using DSS
overlay manager's Color Phase Rotation matrix. The CPR matrix does not
exactly match the CTM property documentation. On DSS the CPR matrix is
applied after gamma table look up. However, it seems stupid to add a
custom property just for that.

Signed-off-by: Jyri Sarha <jsarha at ti.com>
---
There was an earlier version of this patch as a part of one series here:
https://lists.freedesktop.org/archives/dri-devel/2017-March/136811.html

Changes since that version:
- Fix commit message: CPR is applied after gamma table, not before
   (this makes me wonder if we should call our gamma tablem degamma)
- Correctly convert form signed magnitude format of CTM blob
- Remove redundant size check for CTM blob

 drivers/gpu/drm/omapdrm/omap_crtc.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c b/drivers/gpu/drm/omapdrm/omap_crtc.c
index dccd037..24a2d14 100644
--- a/drivers/gpu/drm/omapdrm/omap_crtc.c
+++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
@@ -312,6 +312,32 @@ void omap_crtc_vblank_irq(struct drm_crtc *crtc)
 	DBG("%s: apply done", omap_crtc->name);
 }
 
+static s16 omap_crtc_S31_32_to_s2_8(s64 coef)
+{
+	uint64_t sign_bit = 1ULL << 63;
+	uint64_t cbits = (uint64_t) coef;
+	s16 ret = clamp_val(((cbits & ~sign_bit) >> 24), 0, 0x1FF);
+
+	if (cbits & sign_bit)
+		ret = -ret;
+
+	return ret;
+}
+
+static void omap_crtc_cpr_coefs_from_ctm(const struct drm_color_ctm *ctm,
+					 struct omap_dss_cpr_coefs *cpr)
+{
+	cpr->rr = omap_crtc_S31_32_to_s2_8(ctm->matrix[0]);
+	cpr->rg = omap_crtc_S31_32_to_s2_8(ctm->matrix[1]);
+	cpr->rb = omap_crtc_S31_32_to_s2_8(ctm->matrix[2]);
+	cpr->gr = omap_crtc_S31_32_to_s2_8(ctm->matrix[3]);
+	cpr->gg = omap_crtc_S31_32_to_s2_8(ctm->matrix[4]);
+	cpr->gb = omap_crtc_S31_32_to_s2_8(ctm->matrix[5]);
+	cpr->br = omap_crtc_S31_32_to_s2_8(ctm->matrix[6]);
+	cpr->bg = omap_crtc_S31_32_to_s2_8(ctm->matrix[7]);
+	cpr->bb = omap_crtc_S31_32_to_s2_8(ctm->matrix[8]);
+}
+
 static void omap_crtc_write_crtc_properties(struct drm_crtc *crtc)
 {
 	struct omap_drm_private *priv = crtc->dev->dev_private;
@@ -325,6 +351,14 @@ static void omap_crtc_write_crtc_properties(struct drm_crtc *crtc)
 	info.partial_alpha_enabled = false;
 	info.cpr_enable = false;
 
+	if (crtc->state->ctm) {
+		struct drm_color_ctm *ctm =
+			(struct drm_color_ctm *) crtc->state->ctm->data;
+
+		info.cpr_enable = true;
+		omap_crtc_cpr_coefs_from_ctm(ctm, &info.cpr_coefs);
+	}
+
 	priv->dispc_ops->mgr_setup(omap_crtc->channel, &info);
 }
 
@@ -636,7 +670,7 @@ struct drm_crtc *omap_crtc_init(struct drm_device *dev,
 	if (priv->dispc_ops->mgr_gamma_size(channel)) {
 		uint gamma_lut_size = 256;
 
-		drm_crtc_enable_color_mgmt(crtc, 0, false, gamma_lut_size);
+		drm_crtc_enable_color_mgmt(crtc, 0, true, gamma_lut_size);
 		drm_mode_crtc_set_gamma_size(crtc, gamma_lut_size);
 	}
 
-- 
1.9.1