[PATCH] drm/amd/display: Retry link training if preferred settings not used

[Harry Wentland]

On 2018-07-13 01:40 PM, Bhawanpreet Lakha wrote:
> Some receivers seem to fail the first link training but are good on
> subsequent tries. Check if the max setting was good otherwise retry
> link training.
> 
> This fixes HTC vive pro issue where it would fail to light up after
> being disabled.
> 
> Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>

Reviewed-by: Harry Wentland <harry.wentland at amd.com>

Harry

> ---
>  drivers/gpu/drm/amd/display/dc/core/dc_link.c    | 21 +++++++++++++++++++--
>  drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c |  9 ++++++---
>  drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h  |  3 ++-
>  3 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> index 4de68fa074a0..34ab1a91baab 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> @@ -60,7 +60,14 @@
>  
>  enum {
>  	LINK_RATE_REF_FREQ_IN_MHZ = 27,
> -	PEAK_FACTOR_X1000 = 1006
> +	PEAK_FACTOR_X1000 = 1006,
> +	/*
> +	 * Some receivers fail to train on first try and are good
> +	 * on subsequent tries. 2 retries should be plenty. If we
> +	 * don't have a successful training then we don't expect to
> +	 * ever get one.
> +	 */
> +	LINK_TRAINING_MAX_VERIFY_RETRY = 2
>  };
>  
>  /*******************************************************************************
> @@ -760,7 +767,17 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
>  				 */
>  
>  				/* deal with non-mst cases */
> -				dp_hbr_verify_link_cap(link, &link->reported_link_cap);
> +				for (i = 0; i < LINK_TRAINING_MAX_VERIFY_RETRY; i++) {
> +					int fail_count = 0;
> +
> +					dp_hbr_verify_link_cap(link,
> +							      &link->reported_link_cap,
> +							      &fail_count);
> +
> +					if (fail_count == 0)
> +						break;
> +				}
> +
>  			}
>  
>  			/* HDMI-DVI Dongle */
> 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 8fbb999e4a8a..18258944f442 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
> @@ -1088,7 +1088,8 @@ static struct dc_link_settings get_max_link_cap(struct dc_link *link)
>  
>  bool dp_hbr_verify_link_cap(
>  	struct dc_link *link,
> -	struct dc_link_settings *known_limit_link_setting)
> +	struct dc_link_settings *known_limit_link_setting,
> +	int *fail_count)
>  {
>  	struct dc_link_settings max_link_cap = {0};
>  	struct dc_link_settings cur_link_setting = {0};
> @@ -1146,15 +1147,17 @@ bool dp_hbr_verify_link_cap(
>  				cur);
>  
>  
> -		if (skip_link_training)
> +		if (skip_link_training) {
>  			success = true;
> -		else {
> +		} else {
>  			status = dc_link_dp_perform_link_training(
>  							link,
>  							cur,
>  							skip_video_pattern);
>  			if (status == LINK_TRAINING_SUCCESS)
>  				success = true;
> +			else
> +				(*fail_count)++;
>  		}
>  
>  		if (success)
> diff --git a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h
> index 2f783c650084..5eed19153de5 100644
> --- a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h
> +++ b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h
> @@ -35,7 +35,8 @@ struct dc_link_settings;
>  
>  bool dp_hbr_verify_link_cap(
>  	struct dc_link *link,
> -	struct dc_link_settings *known_limit_link_setting);
> +	struct dc_link_settings *known_limit_link_setting,
> +	int *fail_count);
>  
>  bool dp_validate_mode_timing(
>  	struct dc_link *link,
>