drm/mediatek: ovl: Add blend_modes to driver data

OVL_CON_CLRFMT_MAN is a configuration for extending color format
settings of DISP_REG_OVL_CON(n).
It will change some of the original color format settings.

Take the settings of (3 << 12) for example.
- If OVL_CON_CLRFMT_MAN = 0 means OVL_CON_CLRFMT_RGBA8888.
- If OVL_CON_CLRFMT_MAN = 1 means OVL_CON_CLRFMT_PARGB8888.

Since previous SoCs did not support OVL_CON_CLRFMT_MAN, this means
that the SoC does not support the premultiplied color format.
It will break the original color format setting of MT8173.

Therefore, the blend_modes is added to the driver data and then
mtk_ovl_fmt_convert() will check the blend_modes to see if
pre-multiplied is supported in the current platform.
If it is not supported, use coverage mode to set it to the supported
color formats to solve the degradation problem.

Fixes: a3f7f7e ("drm/mediatek: Support "Pre-multiplied" blending in OVL")
Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20241009034646.13143-5-jason-jh.lin@mediatek.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Author: Jason-JH.Lin

drivers/gpu/drm/mediatek/mtk_disp_ovl.c

@@ -146,6 +146,7 @@ struct mtk_disp_ovl_data {
 	bool fmt_rgb565_is_0;
 	bool smi_id_en;
 	bool supports_afbc;
+	const u32 blend_modes;
 	const u32 *formats;
 	size_t num_formats;
 	bool supports_clrfmt_ext;
@@ -386,9 +387,27 @@ void mtk_ovl_layer_off(struct device *dev, unsigned int idx,
 		      DISP_REG_OVL_RDMA_CTRL(idx));
 }
 
-static unsigned int ovl_fmt_convert(struct mtk_disp_ovl *ovl, unsigned int fmt,
-				    unsigned int blend_mode)
+static unsigned int mtk_ovl_fmt_convert(struct mtk_disp_ovl *ovl,
+					struct mtk_plane_state *state)
 {
+	unsigned int fmt = state->pending.format;
+	unsigned int blend_mode = DRM_MODE_BLEND_COVERAGE;
+
+	/*
+	 * For the platforms where OVL_CON_CLRFMT_MAN is defined in the hardware data sheet
+	 * and supports premultiplied color formats, such as OVL_CON_CLRFMT_PARGB8888.
+	 *
+	 * Check blend_modes in the driver data to see if premultiplied mode is supported.
+	 * If not, use coverage mode instead to set it to the supported color formats.
+	 *
+	 * Current DRM assumption is that alpha is default premultiplied, so the bitmask of
+	 * blend_modes must include BIT(DRM_MODE_BLEND_PREMULTI). Otherwise, mtk_plane_init()
+	 * will get an error return from drm_plane_create_blend_mode_property() and
+	 * state->base.pixel_blend_mode should not be used.
+	 */
+	if (ovl->data->blend_modes & BIT(DRM_MODE_BLEND_PREMULTI))
+		blend_mode = state->base.pixel_blend_mode;
+
 	switch (fmt) {
 	default:
 	case DRM_FORMAT_RGB565:
@@ -466,7 +485,7 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
 		return;
 	}
 
-	con = ovl_fmt_convert(ovl, fmt, blend_mode);
+	con = mtk_ovl_fmt_convert(ovl, state);
 	if (state->base.fb) {
 		con |= state->base.alpha & OVL_CON_ALPHA;
 
@@ -664,6 +683,9 @@ static const struct mtk_disp_ovl_data mt8192_ovl_driver_data = {
 	.layer_nr = 4,
 	.fmt_rgb565_is_0 = true,
 	.smi_id_en = true,
+	.blend_modes = BIT(DRM_MODE_BLEND_PREMULTI) |
+		       BIT(DRM_MODE_BLEND_COVERAGE) |
+		       BIT(DRM_MODE_BLEND_PIXEL_NONE),
 	.formats = mt8173_formats,
 	.num_formats = ARRAY_SIZE(mt8173_formats),
 };
@@ -674,6 +696,9 @@ static const struct mtk_disp_ovl_data mt8192_ovl_2l_driver_data = {
 	.layer_nr = 2,
 	.fmt_rgb565_is_0 = true,
 	.smi_id_en = true,
+	.blend_modes = BIT(DRM_MODE_BLEND_PREMULTI) |
+		       BIT(DRM_MODE_BLEND_COVERAGE) |
+		       BIT(DRM_MODE_BLEND_PIXEL_NONE),
 	.formats = mt8173_formats,
 	.num_formats = ARRAY_SIZE(mt8173_formats),
 };
@@ -685,6 +710,9 @@ static const struct mtk_disp_ovl_data mt8195_ovl_driver_data = {
 	.fmt_rgb565_is_0 = true,
 	.smi_id_en = true,
 	.supports_afbc = true,
+	.blend_modes = BIT(DRM_MODE_BLEND_PREMULTI) |
+		       BIT(DRM_MODE_BLEND_COVERAGE) |
+		       BIT(DRM_MODE_BLEND_PIXEL_NONE),
 	.formats = mt8195_formats,
 	.num_formats = ARRAY_SIZE(mt8195_formats),
 	.supports_clrfmt_ext = true,