[PATCH] drm/amd/display: Don't disable DP PHY when link loss happens

[Harry Wentland]

On 2019-12-23 3:46 p.m., Zhan Liu wrote:
> [Why]
> There is a use case that link loss happens accidentally,
> and we need to recover that link loss as soon as possible.
> Under this circumstance, DP PHY will perform link training,
> then try to recover the link that's just lost.
> 
> However, if link PHY is disabled by code here, then
> DP display will never come back again.
> 
> [How]
> Don't disable DP transmitter and its encoder, even if
> link loss is detected.
> 
> Signed-off-by: Zhan Liu <zhan.liu at amd.com>
> ---
>  drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> index 38b0f4347383..49f48d432923 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
> @@ -2876,7 +2876,6 @@ bool dc_link_handle_hpd_rx_irq(struct dc_link *link, union hpd_irq_data *out_hpd
>  			return false;
>  
>  		previous_link_settings = link->cur_link_settings;
> -		dp_disable_link_phy(link, pipe_ctx->stream->signal);

Have you synced with Paul to make sure this doesn't regress his patch?
We don't want to break USB-C displays again.

It sounds like that dp_disable_link_phy was added here for a reason but
it's hard to see from Paul's patch whether this line is integral or
incidental.

Harry

>  
>  		perform_link_training_with_retries(&previous_link_settings,
>  			true, LINK_TRAINING_ATTEMPTS,
>