[PATCH V4] drm/dp_mst: Retrieve extended DPCD caps for topology manager

[Lyude Paul]

One last change I realized we should do is print the name of the AUX adapter
in question. I don't mind just adding that myself before I push it though so
you don't need to send a respin.

Going to go push this to drm-misc-next, thanks!

On Tue, 2020-09-22 at 14:53 +0800, Koba Ko wrote:
> As per DP-1.3, First check DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT.
> If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 1,read the DP_DP13_DPCD_REV to
> get the faster capability.
> If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 0,read DP_DPCD_REV.
> 
> Signed-off-by: Koba Ko <koba.ko at canonical.com>
> Reviewed-by: Lyude Paul <lyude at redhat.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index e87542533640..63f8809b9aa4 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3686,9 +3686,9 @@ int drm_dp_mst_topology_mgr_set_mst(struct
> drm_dp_mst_topology_mgr *mgr, bool ms
>  		WARN_ON(mgr->mst_primary);
>  
>  		/* get dpcd info */
> -		ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd,
> DP_RECEIVER_CAP_SIZE);
> -		if (ret != DP_RECEIVER_CAP_SIZE) {
> -			DRM_DEBUG_KMS("failed to read DPCD\n");
> +		ret = drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd);
> +		if (ret < 0) {
> +			drm_dbg_kms(mgr->dev, "failed to read DPCD, ret %d\n",
> ret);
>  			goto out_unlock;
>  		}
>  
-- 
Cheers,
	Lyude Paul (she/her)
	Software Engineer at Red Hat