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

[Yin, Tianci (Rico)]

[AMD Official Use Only]

Thank you very much Harry!

Regards,
Rico
________________________________
From: Wentland, Harry <Harry.Wentland at amd.com>
Sent: Tuesday, March 8, 2022 21:55
To: Yin, Tianci (Rico) <Tianci.Yin at amd.com>; amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Wang, Yu (Charlie) <Yu.Wang4 at amd.com>; Zhuo, Qingqing (Lillian) <Qingqing.Zhuo at amd.com>; Liu, Wenjing <Wenjing.Liu at amd.com>; Chen, Guchun <Guchun.Chen at amd.com>
Subject: Re: [PATCH] drm/amd/display: fix dp kvm can't light up

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;
>                }
>

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