[PATCH v2 07/23] drm/amd/display: Update training parameters for DPIA links

[Harry Wentland]

On 2021-10-05 03:51, Wayne Lin wrote:
> From: Jimmy Kizito <Jimmy.Kizito at amd.com>
> 
> [why & how]
> Add codes for commit "ede4f6dac99e drm/amd/display: Update
> setting of DP training parameters." to support USB4 DP tunneling
> feature
> 

Suggested title: Skip DPCD read for DPTX-to-DPIA hop

Suggested description: Driver does not need to train the first hop.

Harry

> Reviewed-by: Jun Lei <Jun.Lei at amd.com>
> Acked-by: Wayne Lin <Wayne.Lin at amd.com>
> Acked-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
> Signed-off-by: Jimmy Kizito <Jimmy.Kizito at amd.com>
> ---
>  drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> 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 9bc5f49ea2ec..dd1d0262ba40 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
> @@ -1777,6 +1777,13 @@ static enum dc_status configure_lttpr_mode_non_transparent(
>  
>  		if (encoding == DP_8b_10b_ENCODING) {
>  			repeater_cnt = dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt);
> +
> +			/* Driver does not need to train the first hop. Skip DPCD read and clear
> +			 * AUX_RD_INTERVAL for DPTX-to-DPIA hop.
> +			 */
> +			if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA)
> +				link->dpcd_caps.lttpr_caps.aux_rd_interval[--repeater_cnt] = 0;
> +
>  			for (repeater_id = repeater_cnt; repeater_id > 0; repeater_id--) {
>  				aux_interval_address = DP_TRAINING_AUX_RD_INTERVAL_PHY_REPEATER1 +
>  							((DP_REPEATER_CONFIGURATION_AND_STATUS_SIZE) * (repeater_id - 1));
>