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[2001:14ba:a073:af00:264b:feff:fe8b:be8a]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5b46cf95803sm836861e87.1.2026.08.17.20.22.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 20:22:10 -0700 (PDT) Date: Tue, 18 Aug 2026 06:22:07 +0300 From: Dmitry Baryshkov To: Yongxing Mou Cc: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , Rob Clark , Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Sean Paul , Marijn Suijten , Tomi Valkeinen , Bjorn Andersson , Konrad Dybcio , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org Subject: Re: [PATCH 3/5] drm/msm/dp: suppress bridge hotplug events during MST operation Message-ID: References: <20260629-msm-dp-msttypec-v1-0-646a10256233@oss.qualcomm.com> <20260629-msm-dp-msttypec-v1-3-646a10256233@oss.qualcomm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Proofpoint-GUID: YzzgAe2dtU9pqz2vAnKleV2GZcT6AGj5 X-Proofpoint-ORIG-GUID: YzzgAe2dtU9pqz2vAnKleV2GZcT6AGj5 X-Proofpoint-Spam-Info: AW1haW4tMjYwODE4MDAyMyBTYWx0ZWRfX244WllxvW8pt 8G5X4OjnCMmHnHYTlEQ74AlZe1GeITVkAi/bFfp0pvwtWEq1Yfn3TT0PdSXH99v/bEunyac59Y9 L1UBwZYwYhtsv/W+EajfTMd/00wT+VE= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE4MDAyMyBTYWx0ZWRfX53fx7wiSXzbI mMtpzWAKeDedsxBWCDxW6LKUA2CnfcHR2Wm/X8FoBuBNdP/V7DsH6+J/Uqi97/tB0DMIWkdXiwB XfFN/P5X+1XVRd6nDaPoz5Z5jNyY91elApmNuAPF26vMGzmJyb15XOgmTzZ7G5dp2cabnNRngaO gH/gFKV8SoYWzuCSVF1qREjh96kkIyaVruxiNwfMiRRotftTCcvyUniNFanVdv9EuoM5MnFQ35o I2qb5RcyRk+QRog8cg1OhyK3voILCJifAOUEbQprbeMfRvFWdblw52PsyyKp157ckhlPMG092vo LFk3bgEpyUCjK8zbZ2hrePLUtGAKBufIkMGeq2FZTWrWkJvWbFbbTCB+pujjARkmMkvllD9Toqp JMdKx5ZvpvrC02iYR3dCraScxXN967SDFkE4pVGIyBHKwwO+xGo4B5rG1coXEMXwuj89SXFsWbw a6f6Gzs1323WIasW/sA== X-Authority-Analysis: v=2.4 cv=UslT8ewB c=1 sm=1 tr=0 ts=6a83cfe5 cx=c_pps a=HLyN3IcIa5EE8TELMZ618Q==:117 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=rJkE3RaqiGZ5pbrm-msn:22 a=EUspDBNiAAAA:8 a=pvfFc-ymSHibiSm0GcIA:9 a=CjuIK1q_8ugA:10 a=bTQJ7kPSJx9SKPbeHEYW:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-17_04,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 suspectscore=0 phishscore=0 bulkscore=0 priorityscore=1501 malwarescore=0 spamscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608180023 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260817_202214_581504_8915115C X-CRM114-Status: GOOD ( 34.91 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On Mon, Aug 17, 2026 at 04:01:36PM +0800, Yongxing Mou wrote: > > > On 7/12/2026 6:44 PM, Dmitry Baryshkov wrote: > > On Mon, Jun 29, 2026 at 10:48:05PM +0800, Yongxing Mou wrote: > > > The DP MST framework already generates the required hotplug events for > > > MST topology changes. > > > > > > Suppress connector hotplug event generation from the bridge connector > > > path while MST is active, and continue propagating HPD notifications to > > > the DP driver. > > > > > > Signed-off-by: Yongxing Mou > > > --- > > > drivers/gpu/drm/display/drm_bridge_connector.c | 6 ++++-- > > > drivers/gpu/drm/msm/dp/dp_display.c | 9 ++++++++- > > > > No, it can't go as this. The drm_bridge_connector part should have been > > a part of the first patch. > > > Got it. > > > 2 files changed, 12 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c > > > index 7334d6677604..82ed0dc450ab 100644 > > > --- a/drivers/gpu/drm/display/drm_bridge_connector.c > > > +++ b/drivers/gpu/drm/display/drm_bridge_connector.c > > > @@ -162,6 +162,7 @@ static void drm_bridge_connector_handle_hpd(struct drm_bridge_connector *drm_bri > > > { > > > struct drm_connector *connector = &drm_bridge_connector->base; > > > struct drm_device *dev = connector->dev; > > > + bool send_hotplug = true; > > > /* > > > * IRQ-only notification: extra_status carries the event but > > > @@ -179,9 +180,10 @@ static void drm_bridge_connector_handle_hpd(struct drm_bridge_connector *drm_bri > > > connector->status = status; > > > mutex_unlock(&dev->mode_config.mutex); > > > - drm_bridge_connector_hpd_notify(connector, status, extra_status, NULL); > > > + drm_bridge_connector_hpd_notify(connector, status, extra_status, &send_hotplug); > > > - drm_kms_helper_connector_hotplug_event(connector); > > > + if (send_hotplug) > > > + drm_kms_helper_connector_hotplug_event(connector); > > > > But now I can also see that the idea seems to be incorrect. You are > > preventing the kernel from sending the events, but it doesn't really > > matter. If connection status oscillates, then other components might > > notice it even without the event being sent. > > > Here our original intent behind suppressing the hotplug was > that, under MST, hotplugs should be sent independently by the MST > framework, rather than being emitted along the IRQ handling path. > > Following the extra_status approach you introduced, would it make sense > to let the bridge_connector layer distinguish between long pulses (HPD) > and short pulses (IRQ_HPD) -- a short pulse would not update > connector->status and would not emit a hotplug, only forwarding the > event to the bridge driver. Does this direction sound reasonable to > you? IRQ_HPD is not limited to the MST usecase. > > > > > } > > > static void drm_bridge_connector_hpd_cb(void *cb_data, > > > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c > > > index 6835c68fe510..bc93b566fbca 100644 > > > --- a/drivers/gpu/drm/msm/dp/dp_display.c > > > +++ b/drivers/gpu/drm/msm/dp/dp_display.c > > > @@ -1790,10 +1790,17 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge, > > > msm_dp_hpd_plug_handle(dp); > > > } else { > > > msm_dp_hpd_plug_handle(dp); > > > + /* mst_active is set in plug_handle; suppress SST hotplug */ > > > + if (send_hotplug && msm_dp_display->mst_active) > > > + *send_hotplug = false; > > > } > > > } else { > > > - if (hpd_link_status == ISR_DISCONNECTED) > > > + if (!msm_dp_display->mst_active) { > > > msm_dp_hpd_unplug_handle(dp); > > > + } else if (send_hotplug) { > > > + msm_dp_hpd_unplug_handle(dp); > > > + *send_hotplug = false; > > > > Why? Disconnected events definitely should be reported further. > > > In MST case, MST DRM framework will send the discconnected hotplug by > msm_dp_mst_display_set_mgr_state(&dp->msm_dp_display, false);. msm_dp_mst_display_set_mgr_state() is not a part of MST DRM framework. But, while we are at it. The MST framwork needs to be updated to send connector-specific HPD events. > > > + } > > > } > > > pm_runtime_put_sync(&msm_dp_display->pdev->dev); > > > > > > -- > > > 2.43.0 > > > > > > -- With best wishes Dmitry _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic