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%3Ba=su...

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@vger.kernel.org know about it.

From foo@baz Wed Dec 20 18:17:52 CET 2017

From: Eric Anholt eric@anholt.net 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@anholt.net

[ 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@an... 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 | 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@anholt.net are

queue-4.14/drm-vc4-avoid-using-vrefresh-0-mode-in-dsi-htotal-math.patch