drm/vc4: Avoid using vrefresh==0 mode in DSI htotal math.
authorEric Anholt <eric@anholt.net>
Tue, 15 Aug 2017 23:47:19 +0000 (16:47 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 25 Dec 2017 13:26:30 +0000 (14:26 +0100)
commit0d74c05ca7ef083cbc676aacfd147ff60de54c95
treea79800cbc98ae8d3328a03aef3389bc5d0517da5
parent80879ecb4624d58e10cfe03550056c34483187a5
drm/vc4: Avoid using vrefresh==0 mode in DSI htotal math.

[ 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@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20170815234722.20700-2-eric@anholt.net
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/gpu/drm/vc4/vc4_dsi.c