[PATCH v2 01/10] drm: bridge: dw_hdmi: Disable scrambler feature when not supported

[Neil Armstrong]

On 08/09/2024 15:28, Jonas Karlman wrote:
> The scrambler feature can be left enabled when hotplugging from a sink
> and mode that require scrambling to a sink that does not support SCDC or
> scrambling.
> 
> Typically a blank screen or 'no signal' message can be observed after
> using a HDMI 2.0 4K at 60Hz mode and then hotplugging to a sink that only
> support HDMI 1.4.
> 
> Fix this by disabling the scrambler feature when SCDC is not supported.
> 
> Fixes: 264fce6cc2c1 ("drm/bridge: dw-hdmi: Add SCDC and TMDS Scrambling support")
> Reported-by: Christopher Obbard <chris.obbard at collabora.com>
> Signed-off-by: Jonas Karlman <jonas at kwiboo.se>
> ---
> v2: New patch
> ---
>   drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 0031f3c54882..9e7f86a0bf5c 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -2117,6 +2117,8 @@ static void hdmi_av_composer(struct dw_hdmi *hdmi,
>   				    HDMI_MC_SWRSTZ);
>   			drm_scdc_set_scrambling(hdmi->curr_conn, 0);
>   		}
> +	} else if (hdmi->version >= 0x200a) {
> +		hdmi_writeb(hdmi, 0, HDMI_FC_SCRAMBLER_CTRL);
>   	}
>   
>   	/* Set up horizontal active pixel width */

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