Re: [PATCH v3 1/1] drm: bridge: ti-sn65dsi83: Fix DSI mode flags for stable LVDS output

[Alexander Stein]

Am Sonntag, 12. April 2026, 07:38:11 CEST schrieb Sudarshan Shetty:
> The current DSI mode configuration enables VIDEO_BURST and disables
> horizontal front porch (HFP) and back porch (HBP) transmission using
> MIPI_DSI_MODE_VIDEO_NO_HFP and MIPI_DSI_MODE_VIDEO_NO_HBP.
> 
> However, the SN65DSI83/84 bridge relies on receiving full horizontal
> timing information over DSI in order to correctly reconstruct the LVDS
> output timings. When HFP and HBP are not transmitted, the bridge cannot
> recreate the required timing parameters, resulting in unstable or
> missing display output on some panels.
> 
> Additionally, while burst mode is supported by the hardware, its use
> depends on continuous clock behavior from the DSI host. In practice,
> burst mode may introduce instability depending on the host controller
> implementation, as the DSI link may transition to low-power state
> between bursts.
> 
> In testing, removing burst mode and ensuring full horizontal timing
> transmission results in stable LVDS output across affected panels.
> 
> Update the DSI mode flags to:
>   - Drop MIPI_DSI_MODE_VIDEO_BURST
>   - Drop MIPI_DSI_MODE_VIDEO_NO_HFP
>   - Drop MIPI_DSI_MODE_VIDEO_NO_HBP
> 
> This aligns with common system configurations where non-burst mode is
> preferred and full timing information is transmitted over DSI.
> 
> Signed-off-by: Sudarshan Shetty <tessolveupstream@xxxxxxxxx>

Tested-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxx># imx8mq, imx8mm, imx8mm

on both tm070jvhg33 and g133han01 displays.

Best regards
Alexander

> ---
>  drivers/gpu/drm/bridge/ti-sn65dsi83.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> index fef6bca3273f..9d51dc2b75bc 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> @@ -976,9 +976,8 @@ static int sn65dsi83_host_attach(struct sn65dsi83 *ctx)
>  
>  	dsi->lanes = dsi_lanes;
>  	dsi->format = MIPI_DSI_FMT_RGB888;
> -	dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
> -			  MIPI_DSI_MODE_VIDEO_NO_HFP | MIPI_DSI_MODE_VIDEO_NO_HBP |
> -			  MIPI_DSI_MODE_VIDEO_NO_HSA | MIPI_DSI_MODE_NO_EOT_PACKET;
> +	dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_NO_HSA |
> +			  MIPI_DSI_MODE_NO_EOT_PACKET;
>  
>  	ret = devm_mipi_dsi_attach(dev, dsi);
>  	if (ret < 0) {
> 


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