[media] v4l: vsp1: Add support for the RPF alpha multiplier on Gen3

The Gen3 RPF includes an alpha multiplier that can both multiply the
alpha channel by a fixed global alpha value, and multiply the pixel
components to convert the input to premultiplied alpha.

As alpha premultiplication is available in the BRU for both Gen2 and
Gen3 we handle it there and use the Gen3 alpha multiplier for global
alpha multiplication only. This prevents conversion to premultiplied
alpha if no BRU is present in the pipeline, that use case will be
implemented later if needed.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 54 insertions, 3 deletions

diff --git a/drivers/media/platform/vsp1/vsp1_rpf.c b/drivers/media/platform/vsp1/vsp1_rpf.c
index 5486ff54a2b3..49168db3f529 100644
--- a/drivers/media/platform/vsp1/vsp1_rpf.c
+++ b/drivers/media/platform/vsp1/vsp1_rpf.c
@@ -141,9 +141,27 @@ static void rpf_configure(struct vsp1_entity *entity,
 		       (left << VI6_RPF_LOC_HCOORD_SHIFT) |
 		       (top << VI6_RPF_LOC_VCOORD_SHIFT));
 
-	/* Use the alpha channel (extended to 8 bits) when available or an
-	 * alpha value set through the V4L2_CID_ALPHA_COMPONENT control
-	 * otherwise. Disable color keying.
+	/* On Gen2 use the alpha channel (extended to 8 bits) when available or
+	 * a fixed alpha value set through the V4L2_CID_ALPHA_COMPONENT control
+	 * otherwise.
+	 *
+	 * The Gen3 RPF has extended alpha capability and can both multiply the
+	 * alpha channel by a fixed global alpha value, and multiply the pixel
+	 * components to convert the input to premultiplied alpha.
+	 *
+	 * As alpha premultiplication is available in the BRU for both Gen2 and
+	 * Gen3 we handle it there and use the Gen3 alpha multiplier for global
+	 * alpha multiplication only. This however prevents conversion to
+	 * premultiplied alpha if no BRU is present in the pipeline. If that use
+	 * case turns out to be useful we will revisit the implementation (for
+	 * Gen3 only).
+	 *
+	 * We enable alpha multiplication on Gen3 using the fixed alpha value
+	 * set through the V4L2_CID_ALPHA_COMPONENT control when the input
+	 * contains an alpha channel. On Gen2 the global alpha is ignored in
+	 * that case.
+	 *
+	 * In all cases, disable color keying.
 	 */
 	vsp1_rpf_write(rpf, dl, VI6_RPF_ALPH_SEL, VI6_RPF_ALPH_SEL_AEXT_EXT |
 		       (fmtinfo->alpha ? VI6_RPF_ALPH_SEL_ASEL_PACKED
@@ -152,10 +170,43 @@ static void rpf_configure(struct vsp1_entity *entity,
 	vsp1_rpf_write(rpf, dl, VI6_RPF_VRTCOL_SET,
 		       rpf->alpha << VI6_RPF_VRTCOL_SET_LAYA_SHIFT);
 
+	if (entity->vsp1->info->gen == 3) {
+		u32 mult;
+
+		if (fmtinfo->alpha) {
+			/* When the input contains an alpha channel enable the
+			 * alpha multiplier. If the input is premultiplied we
+			 * need to multiply both the alpha channel and the pixel
+			 * components by the global alpha value to keep them
+			 * premultiplied. Otherwise multiply the alpha channel
+			 * only.
+			 */
+			bool premultiplied = format->flags
+					   & V4L2_PIX_FMT_FLAG_PREMUL_ALPHA;
+
+			mult = VI6_RPF_MULT_ALPHA_A_MMD_RATIO
+			     | (premultiplied ?
+				VI6_RPF_MULT_ALPHA_P_MMD_RATIO :
+				VI6_RPF_MULT_ALPHA_P_MMD_NONE)
+			     | (rpf->alpha << VI6_RPF_MULT_ALPHA_RATIO_SHIFT);
+		} else {
+			/* When the input doesn't contain an alpha channel the
+			 * global alpha value is applied in the unpacking unit,
+			 * the alpha multiplier isn't needed and must be
+			 * disabled.
+			 */
+			mult = VI6_RPF_MULT_ALPHA_A_MMD_NONE
+			     | VI6_RPF_MULT_ALPHA_P_MMD_NONE;
+		}
+
+		vsp1_rpf_write(rpf, dl, VI6_RPF_MULT_ALPHA, mult);
+	}
+
 	vsp1_pipeline_propagate_alpha(pipe, &rpf->entity, dl, rpf->alpha);
 
 	vsp1_rpf_write(rpf, dl, VI6_RPF_MSK_CTRL, 0);
 	vsp1_rpf_write(rpf, dl, VI6_RPF_CKEY_CTRL, 0);
+
 }
 
 static const struct vsp1_entity_operations rpf_entity_ops = {