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SubjectRe: [PATCH v3] drm/dp_mst: Retrieve extended DPCD caps for topology manager
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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@canonical.com>
> Reviewed-by: Lyude Paul <lyude@redhat.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

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