Re: [PATCH 2/2] drm/bridge/tc358775: Fix DSI clock division for vsync delay calculation

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Reviewed-by: Vinay Simha BN <simhavcs@xxxxxxxxx>

On Thu, Jun 16, 2022 at 3:55 AM Jiri Vanek <jirivanek1@xxxxxxxxx> wrote:
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@xxxxxxxxx>
Signed-off-by: Jiri Vanek <jirivanek1@xxxxxxxxx>
---
 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 cd2721ab02a9..fecb8558b49a 100644
--- a/drivers/gpu/drm/bridge/tc358775.c
+++ b/drivers/gpu/drm/bridge/tc358775.c
@@ -430,7 +430,7 @@ 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;
--
2.30.2



--
regards,
vinaysimha

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