New subject: [Intel-gfx] [PATCH] drm/edid: Fix off-by-one in DispID DTD pixel clock

23 Apr 2020

From: Ville Syrjälä ville.syrjala@linux.intel.com
The DispID DTD pixel clock is documented as:
"00 00 00 h → FF FF FF h | Pixel clock ÷ 10,000 0.01 → 167,772.16 Mega Pixels per Sec"
Which seems to imply that we to add one to the raw value.
Reality seems to agree as there are tiled displays in the wild
which currently show a 10kHz difference in the pixel clock
between the tiles (one tile gets its mode from the base EDID,
the other from the DispID block).
Cc: stable@vger.kernel.org
References: https://gitlab.freedesktop.org/drm/intel/-/issues/27
Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com
---
 drivers/gpu/drm/drm_edid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 43b6ca364daa..544d2603f5fc 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5120,7 +5120,7 @@ static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *d
    struct drm_display_mode *mode;
    unsigned pixel_clock = (timings->pixel_clock[0] |
    			(timings->pixel_clock[1] << 8) |
-				(timings->pixel_clock[2] << 16));
+				(timings->pixel_clock[2] << 16)) + 1;
    unsigned hactive = (timings->hactive[0] | timings->hactive[1] << 8) + 1;
    unsigned hblank = (timings->hblank[0] | timings->hblank[1] << 8) + 1;
    unsigned hsync = (timings->hsync[0] | (timings->hsync[1] & 0x7f) << 8) + 1;
-- 
2.24.1


    