[PATCH 15/24] drm/msm/dp: do not reject wide-bus modes while a YUV420 mode is active

[Dmitry Baryshkov]

msm_dp_bridge_mode_valid() halves the candidate mode's pixel clock when
the sink either uses YUV 420 output or drives the wide bus, so that modes
relying on those to stay under DP_MAX_PIXEL_CLK_KHZ are accepted. The
wide bus part is queried through msm_dp_wide_bus_available(), which
returns false whenever the currently committed mode uses YUV 420 output:
it inspects the stored msm_dp_mode.out_fmt_is_yuv_420 of the active mode,
not the mode being validated.

Consequently, while a YUV 420 mode is active, an RGB mode that needs the
wide bus to fit under DP_MAX_PIXEL_CLK_KHZ has its pixel clock left
un-halved and is wrongly rejected as MODE_CLOCK_HIGH.

The candidate mode's YUV 420 status is already evaluated as is_yuv_420,
and the wide bus is disabled precisely for YUV 420 output, so halving the
pixel clock for either case is equivalent to halving it when the
candidate is YUV 420 or the controller supports the wide bus. Test
wide_bus_supported directly, so the decision no longer depends on the
format of the active mode.

Fixes: df9cf852ca30 ("drm/msm/dp: account for widebus and yuv420 during mode validation")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 1baeb9401cfa..bd1354f2c15d 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -722,7 +722,7 @@ enum drm_mode_status msm_dp_bridge_mode_valid(struct drm_bridge *bridge,
 	if (is_yuv_420 && !msm_dp_display->panel->vsc_sdp_supported)
 		return MODE_NO_420;
 
-	if (is_yuv_420 || msm_dp_wide_bus_available(dp))
+	if (is_yuv_420 || msm_dp_display->wide_bus_supported)
 		mode_pclk_khz /= 2;
 
 	if (mode_pclk_khz > DP_MAX_PIXEL_CLK_KHZ)

-- 
2.47.3