This is a note to let you know that I've just added the patch titled
drm/vc4: Avoid using vrefresh==0 mode in DSI htotal math.
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-vc4-avoid-using-vrefresh-0-mode-in-dsi-htotal-math.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Wed Dec 20 18:17:52 CET 2017
From: Eric Anholt <eric@xxxxxxxxxx>
Date: Tue, 15 Aug 2017 16:47:19 -0700
Subject: drm/vc4: Avoid using vrefresh==0 mode in DSI htotal math.
From: Eric Anholt <eric@xxxxxxxxxx>
[ Upstream commit af2eca53206c59ce9308a4f5f46c4a104a179b6b ]
The incoming mode might have a missing vrefresh field if it came from
drmModeSetCrtc(), which the kernel is supposed to calculate using
drm_mode_vrefresh(). We could either use that or the adjusted_mode's
original vrefresh value.
However, we can maintain a more exact vrefresh value (not just the
integer approximation), by scaling by the ratio of our clocks.
v2: Use math suggested by Andrzej Hajda instead.
v3: Simplify math now that adjusted_mode->clock isn't padded.
v4: Drop some parens.
Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20170815234722.20700-2-eric@xxxxxxxxxx
Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/vc4/vc4_dsi.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -866,7 +866,8 @@ static bool vc4_dsi_encoder_mode_fixup(s
adjusted_mode->clock = pixel_clock_hz / 1000 + 1;
/* Given the new pixel clock, adjust HFP to keep vrefresh the same. */
- adjusted_mode->htotal = pixel_clock_hz / (mode->vrefresh * mode->vtotal);
+ adjusted_mode->htotal = adjusted_mode->clock * mode->htotal /
+ mode->clock;
adjusted_mode->hsync_end += adjusted_mode->htotal - mode->htotal;
adjusted_mode->hsync_start += adjusted_mode->htotal - mode->htotal;
Patches currently in stable-queue which might be from eric@xxxxxxxxxx are
queue-4.14/drm-vc4-avoid-using-vrefresh-0-mode-in-dsi-htotal-math.patch