ACK/Cmnt: [PATCH 1/2][SRU][J/OEM-5.14/OEM-5.17] drm/dp/mst: Read the extended DPCD capabilities during system resume

[Stefan Bader]

On 21.06.22 07:34, Koba Ko wrote:
> From: Imre Deak <imre.deak at intel.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1979267
> 
> The WD22TB4 Thunderbolt dock at least will revert its DP_MAX_LINK_RATE
> from HBR3 to HBR2 after system suspend/resume if the DP_DP13_DPCD_REV
> registers are not read subsequently also as required.
> 
> Fix this by reading DP_DP13_DPCD_REV registers as well, matching what is
> done during connector detection. While at it also fix up the same call
> in drm_dp_mst_dump_topology().
> 
> Cc: Lyude Paul <lyude at redhat.com>
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5292
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> Reviewed-by: Jani Nikula <jani.nikula at intel.com>
> Reviewed-by: Lyude Paul <lyude at redhat.com>
> Ref: https://patchwork.freedesktop.org/patch/489424/?series=105101&rev=1
> Signed-off-by: Koba Ko <koba.ko at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---

Landed upstream now as 7a710a8bc909313951eb9252d8419924c771d7c2

>   drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 86d13d6bc4631..e327c14d66cd3 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3860,9 +3860,7 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,
>   	if (!mgr->mst_primary)
>   		goto out_fail;
>   
> -	ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd,
> -			       DP_RECEIVER_CAP_SIZE);
> -	if (ret != DP_RECEIVER_CAP_SIZE) {
> +	if (drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd) < 0) {
>   		drm_dbg_kms(mgr->dev, "dpcd read failed - undocked during suspend?\n");
>   		goto out_fail;
>   	}
> @@ -4893,8 +4891,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
>   		u8 buf[DP_PAYLOAD_TABLE_SIZE];
>   		int ret;
>   
> -		ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, buf, DP_RECEIVER_CAP_SIZE);
> -		if (ret) {
> +		if (drm_dp_read_dpcd_caps(mgr->aux, buf) < 0) {
>   			seq_printf(m, "dpcd read failed\n");
>   			goto out;
>   		}

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