From: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date: Thu, 8 Oct 2015 08:43:33 +0000 (+0300)
Subject: drm/edid: Round to closest when computing the CEA/HDMI alternate clock
X-Git-Tag: v4.14-rc1~4339^2~14^2~6
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9afd808cf3c45810492f2e05b7c422c99edc88cc;p=platform%2Fkernel%2Flinux-rpi.git

drm/edid: Round to closest when computing the CEA/HDMI alternate clock

Rounding to the closest kHz seems like the better option that round
down or up when computing the alternate clock for CEA/HDMI modes.
It'll give us a slightly more accurate clock in some cases.

Not sure why I went for the down+up approach originally. Perhaps
I was thinking we can go back and forth betwen the two frequencies
without introducing errors, but round to closest still maintains
that property.

Cc: Adam Jackson <ajax@redhat.com>
Cc: Clint Taylor <clinton.a.taylor@intel.com>
Cc: Libin Yang <libin.yang@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 977915cf530a..d5d2c03fd136 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2538,9 +2538,9 @@ cea_mode_alternate_clock(const struct drm_display_mode *cea_mode)
 	 * and the 60Hz variant otherwise.
 	 */
 	if (cea_mode->vdisplay == 240 || cea_mode->vdisplay == 480)
-		clock = clock * 1001 / 1000;
+		clock = DIV_ROUND_CLOSEST(clock * 1001, 1000);
 	else
-		clock = DIV_ROUND_UP(clock * 1000, 1001);
+		clock = DIV_ROUND_CLOSEST(clock * 1000, 1001);
 
 	return clock;
 }