drm/edid: Fix off-by-one in DispID DTD pixel clock

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>
Link: https://patchwork.freedesktop.org/patch/msgid/20200423151743.18767-1-ville.syrjala@linux.intel.com
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 116451101426d40e7acf0c8b002ed4bba823378e..4ede08a84e37238ff893e463710410d13a1b0d12 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5111,7 +5111,7 @@ 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;