From: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date: Thu, 23 Apr 2020 15:17:43 +0000 (+0300)
Subject: drm/edid: Fix off-by-one in DispID DTD pixel clock
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=6292b8efe32e6be408af364132f09572aed14382;p=linux.git

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 116451101426d..4ede08a84e372 100644
--- 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;