[PATCH] drm/amd/display: fix dp kvm can't light up

[Harry Wentland]

On 2022-03-08 01:50, Tianci Yin wrote:
> From: "Tianci.Yin" <tianci.yin at amd.com>
> 
> [why]
> The DP KVM failed to light up, since the lttpr_mode is not reset to
> default value when failed to read LTTPR capabilities, and the
> variable max_link_rate retains a initial value zero, this cause variable
> link_rate be assigned to an error value zero, consquently pixel_clock
> get wrong value zero, and kvm can't light up.
> 
> [how]
> Reset lttpr_mode to default value when failed to read LTTPR
> capabilities, so that the link_rate fallbacks to the minimum rate that
> supported by link encoder and sink.
> 
> Signed-off-by: Tianci.Yin <tianci.yin at amd.com>

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

Harry

> ---
>  drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> 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 5688b15ca9e6..f9ae06103241 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
> @@ -5101,6 +5101,7 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link)
>  				sizeof(lttpr_dpcd_data));
>  		if (status != DC_OK) {
>  			DC_LOG_DP2("%s: Read LTTPR caps data failed.\n", __func__);
> +			link->lttpr_mode = LTTPR_MODE_NON_LTTPR;
>  			return false;
>  		}
>