[media] v4l: vsp1: uds: Fix scaling of alpha layer

Pixel color components can be scaled using either bilinear interpolation
or a multitap filter. The multitap filter provides better results, but
can't be selected when the alpha layer need to be scaled down by more
than 1/2.

Disable alpha scaling when the input has a fixed alpha value, and
program the UDS to output a fixed alpha value in that case. This ensures
the multitap filter will be used whenever possible.

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

1 files changed, 36 insertions, 27 deletions

diff --git a/drivers/media/platform/vsp1/vsp1_uds.c b/drivers/media/platform/vsp1/vsp1_uds.c
index 0293bdbb4401..de92ef4944b3 100644
--- a/drivers/media/platform/vsp1/vsp1_uds.c
+++ b/drivers/media/platform/vsp1/vsp1_uds.c
@@ -45,6 +45,11 @@ static inline void vsp1_uds_write(struct vsp1_uds *uds, u32 reg, u32 data)
  * Scaling Computation
  */
 
+void vsp1_uds_set_alpha(struct vsp1_uds *uds, unsigned int alpha)
+{
+	vsp1_uds_write(uds, VI6_UDS_ALPVAL, alpha << VI6_UDS_ALPVAL_VAL0_SHIFT);
+}
+
 /*
  * uds_output_size - Return the output size for an input size and scaling ratio
  * @input: input size in pixels
@@ -105,49 +110,56 @@ static unsigned int uds_compute_ratio(unsigned int input, unsigned int output)
 	return (input - 1) * 4096 / (output - 1);
 }
 
-static void uds_compute_ratios(struct vsp1_uds *uds)
-{
-	struct v4l2_mbus_framefmt *input = &uds->entity.formats[UDS_PAD_SINK];
-	struct v4l2_mbus_framefmt *output =
-		&uds->entity.formats[UDS_PAD_SOURCE];
-
-	uds->hscale = uds_compute_ratio(input->width, output->width);
-	uds->vscale = uds_compute_ratio(input->height, output->height);
-
-	dev_dbg(uds->entity.vsp1->dev, "hscale %u vscale %u\n",
-		uds->hscale, uds->vscale);
-}
-
 /* -----------------------------------------------------------------------------
  * V4L2 Subdevice Core Operations
  */
 
 static int uds_s_stream(struct v4l2_subdev *subdev, int enable)
 {
-	const struct v4l2_mbus_framefmt *format;
 	struct vsp1_uds *uds = to_uds(subdev);
+	const struct v4l2_mbus_framefmt *output;
+	const struct v4l2_mbus_framefmt *input;
+	unsigned int hscale;
+	unsigned int vscale;
+	bool multitap;
 
 	if (!enable)
 		return 0;
 
-	/* Enable multi-tap scaling. */
-	vsp1_uds_write(uds, VI6_UDS_CTRL, VI6_UDS_CTRL_AON | VI6_UDS_CTRL_BC);
+	input = &uds->entity.formats[UDS_PAD_SINK];
+	output = &uds->entity.formats[UDS_PAD_SOURCE];
+
+	hscale = uds_compute_ratio(input->width, output->width);
+	vscale = uds_compute_ratio(input->height, output->height);
+
+	dev_dbg(uds->entity.vsp1->dev, "hscale %u vscale %u\n", hscale, vscale);
+
+	/* Multi-tap scaling can't be enabled along with alpha scaling when
+	 * scaling down with a factor lower than or equal to 1/2 in either
+	 * direction.
+	 */
+	if (uds->scale_alpha && (hscale >= 8192 || vscale >= 8192))
+		multitap = false;
+	else
+		multitap = true;
+
+	vsp1_uds_write(uds, VI6_UDS_CTRL,
+		       (uds->scale_alpha ? VI6_UDS_CTRL_AON : 0) |
+		       (multitap ? VI6_UDS_CTRL_BC : 0));
 
 	vsp1_uds_write(uds, VI6_UDS_PASS_BWIDTH,
-		       (uds_passband_width(uds->hscale)
+		       (uds_passband_width(hscale)
 				<< VI6_UDS_PASS_BWIDTH_H_SHIFT) |
-		       (uds_passband_width(uds->vscale)
+		       (uds_passband_width(vscale)
 				<< VI6_UDS_PASS_BWIDTH_V_SHIFT));
 
 	/* Set the scaling ratios and the output size. */
-	format = &uds->entity.formats[UDS_PAD_SOURCE];
-
 	vsp1_uds_write(uds, VI6_UDS_SCALE,
-		       (uds->hscale << VI6_UDS_SCALE_HFRAC_SHIFT) |
-		       (uds->vscale << VI6_UDS_SCALE_VFRAC_SHIFT));
+		       (hscale << VI6_UDS_SCALE_HFRAC_SHIFT) |
+		       (vscale << VI6_UDS_SCALE_VFRAC_SHIFT));
 	vsp1_uds_write(uds, VI6_UDS_CLIP_SIZE,
-		       (format->width << VI6_UDS_CLIP_SIZE_HSIZE_SHIFT) |
-		       (format->height << VI6_UDS_CLIP_SIZE_VSIZE_SHIFT));
+		       (output->width << VI6_UDS_CLIP_SIZE_HSIZE_SHIFT) |
+		       (output->height << VI6_UDS_CLIP_SIZE_VSIZE_SHIFT));
 
 	return 0;
 }
@@ -280,9 +292,6 @@ static int uds_set_format(struct v4l2_subdev *subdev, struct v4l2_subdev_fh *fh,
 		uds_try_format(uds, fh, UDS_PAD_SOURCE, format, fmt->which);
 	}
 
-	if (fmt->which == V4L2_SUBDEV_FORMAT_ACTIVE)
-		uds_compute_ratios(uds);
-
 	return 0;
 }