[PATCH v2] drm/mediatek: dsi: Add mode_valid callback to DSI bridge

[Shuijing Li <shuijing.li@mediatek.com>]

Support IGT (Intel GPU Tools) in Mediatek DSI driver.
According to the description of MIPI Alliance Specification for D-PHY 
Version 1.1, the maximum supported data rate is 1.5Gbps, so add mode_valid
callback to dsi bridge to filter out the data rate exceeding the
Specification.

Signed-off-by: Shuijing Li <shuijing.li@mediatek.com>
---
Changes in v2:
Correct descriptions of title and commit message.
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 7d5250351193..a494e04f0ddf 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -806,6 +806,25 @@ static void mtk_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge,
 	mtk_dsi_poweroff(dsi);
 }
 
+static enum drm_mode_status
+mtk_dsi_bridge_mode_valid(struct drm_bridge *bridge,
+			  const struct drm_display_info *info,
+			  const struct drm_display_mode *mode)
+{
+	struct mtk_dsi *dsi = bridge_to_dsi(bridge);
+	u32 bpp;
+
+	if (dsi->format == MIPI_DSI_FMT_RGB565)
+		bpp = 16;
+	else
+		bpp = 24;
+
+	if (mode->clock * bpp / dsi->lanes > 1500000)
+		return MODE_CLOCK_HIGH;
+
+	return MODE_OK;
+}
+
 static const struct drm_bridge_funcs mtk_dsi_bridge_funcs = {
 	.attach = mtk_dsi_bridge_attach,
 	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
@@ -815,6 +834,7 @@ static const struct drm_bridge_funcs mtk_dsi_bridge_funcs = {
 	.atomic_pre_enable = mtk_dsi_bridge_atomic_pre_enable,
 	.atomic_post_disable = mtk_dsi_bridge_atomic_post_disable,
 	.atomic_reset = drm_atomic_helper_bridge_reset,
+	.mode_valid = mtk_dsi_bridge_mode_valid,
 	.mode_set = mtk_dsi_bridge_mode_set,
 };
 
-- 
2.40.1