[PATCH AUTOSEL 5.18 35/93] drm/bridge/tc358775: Fix DSI clock division for vsync delay calculation

Sasha Levin
2022-08-11T15:57:36Z

From: Jiri Vanek <jirivanek1@gmail.com>

[ Upstream commit 993a87917c2af59efb0ee1ce43c878ca8790ba1c ]

Use the same PCLK divide option (divide DSI clock to generate pixel clock)
which is set to LVDS Configuration Register (LVCFG) also for a VSync delay
calculation. Without this change an auxiliary variable could underflow
during the calculation for some dual-link LVDS panels and then calculated
VSync delay is wrong. This leads to a shifted picture on a panel.

Tested-by: Jiri Vanek <jirivanek1@gmail.com>
Signed-off-by: Jiri Vanek <jirivanek1@gmail.com>
Reviewed-by: Vinay Simha BN <simhavcs@gmail.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220615222221.1501-3-jirivanek1@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/bridge/tc358775.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/tc358775.c b/drivers/gpu/drm/bridge/tc358775.c
index 695af3badcc7..0cc047d2a8a1 100644
--- a/drivers/gpu/drm/bridge/tc358775.c
+++ b/drivers/gpu/drm/bridge/tc358775.c
@@ -429,7 +429,7 @@ static void tc_bridge_enable(struct drm_bridge *bridge)
val = TC358775_VPCTRL_MSF(1);

dsiclk = mode->crtc_clock * 3 * tc->bpc / tc->num_dsi_lanes / 1000;
- clkdiv = dsiclk / DIVIDE_BY_3 * tc->lvds_link;
+ clkdiv = dsiclk / (tc->lvds_link == DUAL_LINK ? DIVIDE_BY_6 : DIVIDE_BY_3);
byteclk = dsiclk / 4;
t1 = hactive * (tc->bpc * 3 / 8) / tc->num_dsi_lanes;
t2 = ((100000 / clkdiv)) * (hactive + hback_porch + hsync_len + hfront_porch) / 1000;
--
2.35.1