linux-kernel - Re: [PATCH v3] drm/dp_mst: Retrieve extended DPCD caps for topology manager

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Message-ID: <5f99b65c8a092df343c68249f2bce62e4cd0abff.camel@redhat.com>
Date:   Mon, 21 Sep 2020 14:11:24 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Koba Ko <koba.ko@...onical.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     anthony.wong@...onical.com
Subject: Re: [PATCH v3] drm/dp_mst: Retrieve extended DPCD caps for topology
 manager

Hi, sorry I lost track of this until just now. Comments down below:

On Fri, 2020-09-11 at 11:44 +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@...onical.com>
> Reviewed-by: Lyude Paul <lyude@...hat.com>
> ---
> Changelog:
> 1. Adjust the commit message.
> 2. use drm_dbg_kms instead and print the return code.
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 14 +++-----------
>  1 file changed, 3 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 7753c718ddf9..63f8809b9aa4 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3671,8 +3671,6 @@ EXPORT_SYMBOL(drm_dp_read_mst_cap);
>  int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr,
> bool mst_state)
>  {
>  	int ret = 0;
> -	u8 dpcd_ext = 0;
> -	unsigned int dpcd_offset = 0;
>  	struct drm_dp_mst_branch *mstb = NULL;
>  
>  	mutex_lock(&mgr->payload_lock);
> @@ -3686,17 +3684,11 @@ int drm_dp_mst_topology_mgr_set_mst(struct
> drm_dp_mst_topology_mgr *mgr, bool ms
>  		struct drm_dp_payload reset_pay;
>  
>  		WARN_ON(mgr->mst_primary);
> -		drm_dp_dpcd_read(mgr->aux,
> -				 DP_TRAINING_AUX_RD_INTERVAL,
> -				 &dpcd_ext, sizeof(dpcd_ext));
> -
> -		dpcd_offset =
> -			((dpcd_ext & DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT)
> ?  DP_DP13_DPCD_REV : DP_DPCD_REV);


Uh, are you sure you formatted this patch correctly? None of these hunks are present upstream, this looks like it's a diff for the previous version of this patch that you sent out
>  
>  		/* get dpcd info */
> -		ret = drm_dp_dpcd_read(mgr->aux, dpcd_offset, 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