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Tue, 08 Sep 2026 02:17:29 -0700 (PDT) Received: from flyingfox.tail3d542a.ts.net ([2402:a00:163:2ce9:6c87:7904:21fa:8675]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-670f4f6d3cdsm1803318d50.6.2026.09.08.02.17.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2026 02:17:28 -0700 (PDT) From: Vivek Kumar To: Rob Clark , Dmitry Baryshkov , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org Cc: Abhinav Kumar , Jessica Zhang , Sean Paul , Marijn Suijten , Yongxing Mou , Konrad Dybcio , David Airlie , Simona Vetter , linux-kernel@vger.kernel.org, Vivek Kumar Subject: [PATCH v2] drm/msm/dp: don't gate eDP on DP_SINK_COUNT Date: Tue, 8 Sep 2026 14:47:08 +0530 Message-ID: <20260908091708.3123735-1-vk092kumar@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit msm_dp_display_prepare_link(), msm_dp_display_disable(), and msm_dp_hpd_unplug_handle() all treat dp->link->sink_count == 0 as "nothing is connected", and in msm_dp_display_prepare_link() this causes probe/enable to fail outright with -ENOTCONN. This is correct for external DisplayPort, where a compliant sink is required to report a valid DP_SINK_COUNT over the AUX channel. It is not correct for eDP: some eDP sinks -- particularly fixed-format eDP-to-HDMI bridge chips with no downstream AUX-capable panel behind them -- never populate DP_SINK_COUNT with a nonzero value, even while otherwise participating normally in DPCD capability exchange and link training. drm_dp_read_sink_count_cap() already accounts for this by excluding eDP connectors from the sink-count requirement for other DPCD-derived checks (msm_dp_bridge_detect() takes care). Apply the same exemption to the raw sink_count reads in this file via a small shared helper, so eDP outputs with a non-AUX-capable downstream sink are not treated as permanently disconnected. Tested on a Qualcomm QCS6490-based board driving a fixed-format eDP-to-HDMI bridge IC (chrontel,ch7218a) with no negotiable DPCD-capable panel behind it; without this fix, msm_dp_display_prepare_link() unconditionally returns -ENOTCONN and the display never comes up. Fixes: ca16db3d18cf ("drm/msm/dp: break up dp_display_enable into two parts") Signed-off-by: Vivek Kumar --- drivers/gpu/drm/msm/dp/dp_display.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c index bc646d172abe..9254f080f0ea 100644 --- a/drivers/gpu/drm/msm/dp/dp_display.c +++ b/drivers/gpu/drm/msm/dp/dp_display.c @@ -400,6 +400,12 @@ static int msm_dp_display_handle_irq_hpd(struct msm_dp_display_private *dp) return 0; } +static inline bool msm_dp_link_no_sink(struct msm_dp_display_private *dp) +{ + /* eDP sinks are not required to report a valid sink count */ + return !dp->msm_dp_display.is_edp && dp->link->sink_count == 0; +} + static int msm_dp_hpd_plug_handle(struct msm_dp_display_private *dp) { int ret; @@ -467,7 +473,7 @@ static int msm_dp_hpd_unplug_handle(struct msm_dp_display_private *dp) drm_edid_connector_update(dp->msm_dp_display.connector, NULL); /* triggered by irq_hdp with sink_count = 0 */ - if (dp->link->sink_count == 0) + if (msm_dp_link_no_sink(dp)) msm_dp_display_host_phy_exit(dp); /* @@ -634,7 +640,7 @@ static int msm_dp_display_prepare_link(struct msm_dp_display_private *dp) return rc; } - if (dp->link->sink_count == 0) + if (msm_dp_link_no_sink(dp)) return -ENOTCONN; if (!msm_dp_display->power_on) { @@ -723,12 +729,12 @@ static int msm_dp_display_disable(struct msm_dp_display_private *dp, msm_dp_ctrl_off_pixel_clk(dp->ctrl); /* dongle is still connected but sinks are disconnected */ - if (dp->link->sink_count == 0) + if (msm_dp_link_no_sink(dp)) msm_dp_link_psm_config(dp->link, &msm_dp_panel->link_info, true); msm_dp_ctrl_off_link(dp->ctrl, msm_dp_panel); - if (dp->link->sink_count == 0) + if (msm_dp_link_no_sink(dp)) /* re-init the PHY so that we can listen to Dongle disconnect */ msm_dp_ctrl_reinit_phy(dp->ctrl); else -- 2.55.0