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[108.49.102.102]) by smtp.gmail.com with ESMTPSA id 192sm3225151qkn.9.2020.09.09.09.33.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2020 09:33:10 -0700 (PDT) Message-ID: Subject: Re: [PATCH] drm/dp: For MST hub, Get max_link_rate&max_lane from extended rx capability field if EXTENDED_RECEIVER_CAPABILITY_FILED_PRESENT is set. From: Lyude Paul To: Koba Ko , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org, Linux Kernel Mailing List Cc: Anthony Wong Date: Wed, 09 Sep 2020 12:33:09 -0400 In-Reply-To: References: <20200827053053.11271-1-koba.ko@canonical.com> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-1.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We just added a new helper for DPCD retrieval to drm_dp_helper.c (which also handles grabbing the extended receiver caps), we should probably make use of it here On Wed, 2020-09-09 at 14:31 +0800, Koba Ko wrote: > On Thu, Aug 27, 2020 at 1:30 PM Koba Ko wrote: > > Currently, DRM get the capability of the mst hub only from DP_DPCD_REV and > > get the slower speed even the mst hub can run in the faster speed. > > > > 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 > > --- > > drivers/gpu/drm/drm_dp_mst_topology.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c > > b/drivers/gpu/drm/drm_dp_mst_topology.c > > index 67dd72ea200e..3b84c6801281 100644 > > --- a/drivers/gpu/drm/drm_dp_mst_topology.c > > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c > > @@ -3497,6 +3497,8 @@ static int drm_dp_get_vc_payload_bw(u8 dp_link_bw, > > u8 dp_link_count) > > 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); > > @@ -3510,9 +3512,15 @@ 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); > > > > /* get dpcd info */ > > - ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, > > DP_RECEIVER_CAP_SIZE); > > + 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"); > > goto out_unlock; > > -- > > 2.25.1 > > > Add Lyude Paul > -- Cheers, Lyude Paul (she/her) Software Engineer at Red Hat