Re: [PATCH 7/9] drm/bridge: synopsys: dw-mipi-dsi: Disable HSTX and LPRX timeout check

[neil.armstrong@linaro.org]

On 17/07/2023 08:18, Liu Ying wrote:
> According to Synopsys DW MIPI DSI host databook, HSTX and LPRX timeout
> contention detections are measured in TO_CLK_DIVISION cycles.  However,
> the current driver programs magic values to TO_CLK_DIVISION, HSTX_TO_CNT
> and LPRX_TO_CNT register fields, which makes timeout error event wrongly
> happen for some video modes, at least for the typical 1920x1080p@60 video
> mode read from a HDMI monitor driven by ADV7535 DSI to HDMI bridge.
> While at it, the current driver doesn't enable interrupt to handle or
> complain about the error status, so true error just happens silently
> except for display distortions by visual check.
> 
> Disable the timeout check by setting those timeout register fields to
> zero for now until someone comes along with better computations for the
> timeout values.  Although the databook doesn't mention what happens when
> they are set to zero, it turns out the false error doesn't happen for
> the 1920x1080p@60 video mode at least.
> 
> Signed-off-by: Liu Ying <victor.liu@nxp.com>
> ---
>   drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index 536306ccea5a..0fcadf99e783 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -684,7 +684,7 @@ static void dw_mipi_dsi_init(struct dw_mipi_dsi *dsi)
>   	 * timeout clock division should be computed with the
>   	 * high speed transmission counter timeout and byte lane...
>   	 */
> -	dsi_write(dsi, DSI_CLKMGR_CFG, TO_CLK_DIVISION(10) |
> +	dsi_write(dsi, DSI_CLKMGR_CFG, TO_CLK_DIVISION(0) |
>   		  TX_ESC_CLK_DIVISION(esc_clk_division));
>   }
>   
> @@ -747,7 +747,7 @@ static void dw_mipi_dsi_command_mode_config(struct dw_mipi_dsi *dsi)
>   	 * compute high speed transmission counter timeout according
>   	 * to the timeout clock division (TO_CLK_DIVISION) and byte lane...
>   	 */
> -	dsi_write(dsi, DSI_TO_CNT_CFG, HSTX_TO_CNT(1000) | LPRX_TO_CNT(1000));
> +	dsi_write(dsi, DSI_TO_CNT_CFG, HSTX_TO_CNT(0) | LPRX_TO_CNT(0));
>   	/*
>   	 * TODO dw drv improvements
>   	 * the Bus-Turn-Around Timeout Counter should be computed

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>