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[129.46.232.65]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-52db612c2bfsm8319271cf.11.2026.08.17.01.01.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Aug 2026 01:01:55 -0700 (PDT) Message-ID: Date: Mon, 17 Aug 2026 16:01:36 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/5] drm/msm/dp: suppress bridge hotplug events during MST operation To: Dmitry Baryshkov 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 References: <20260629-msm-dp-msttypec-v1-0-646a10256233@oss.qualcomm.com> <20260629-msm-dp-msttypec-v1-3-646a10256233@oss.qualcomm.com> Content-Language: en-US From: Yongxing Mou In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=FqI1OWrq c=1 sm=1 tr=0 ts=6a82bff4 cx=c_pps a=EVbN6Ke/fEF3bsl7X48z0g==:117 a=C3Dk8TwHQYyIj7nOf9RCJw==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=EUspDBNiAAAA:8 a=4e0XemQSoReXIs4U_p4A:9 a=QEXdDO2ut3YA:10 a=a_PwQJl-kcHnX1M80qC6:22 X-Proofpoint-ORIG-GUID: HY3eY8_3MBfBSbT-X1mwBpiMuduMdPSj X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE3MDA1OSBTYWx0ZWRfXy21/jVOSD+6L QZzmyVW8KdGWTM4POTGeemJzx3nnyk+DSkSoFgDeZW+28DtjTfqPteHJZ79yy6+JdiSu1PHZnKT xicFulWXrPTnkb5HsH1FjnP7nWxUku+FaaXFE3t3Vp5jDX8gqgT9oH3mMCvllBzfeqXSBYyzVqq wsolPEYyhPBM3bCQVBllllXWHEk6eui+Fa3rymGP2KpBGa91K9T8Jzep8qiRQ9gbrtvbRqn9qRC HD5taIbdBSmgwCA6AMhOUpeI48iZ1lxbwiXXQ0C6jM97Yv7mYdRX1KtAudSmcwSnKcDfM0iGH2p AwZ1Zage7ajqAnh8VynZ41OrPEYC2CAyaj1hcBk3ZyifcZYgPYLcsKkZAydc40uelmGAjrxGn6q YNOpwbHdVA7q/tK9RH2wfmjWRRhzSvw+j7jxA0Yeon9ZswZeuZrmzv4pokYObx9iMs/go3OMMw+ bNRCRLOHATmuo+eEwng== X-Proofpoint-GUID: HY3eY8_3MBfBSbT-X1mwBpiMuduMdPSj X-Proofpoint-Spam-Info: AW1haW4tMjYwODE3MDA1OSBTYWx0ZWRfX+CzHa5WH+2RC udsVSVEdkvPaD045AErMFR9mUjlgzuQWYqgRB8yzc8HYgfzgunOjx5wGwpWpaA33d2Kjx/vtzBQ J6EJcUeRK7p/jAY+WbF/V1pKGfFLP9k= 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=2026-08-16_06,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 adultscore=0 priorityscore=1501 bulkscore=0 suspectscore=0 clxscore=1015 phishscore=0 lowpriorityscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608170059 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? > >> } >> >> 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);. >> + } >> } >> >> pm_runtime_put_sync(&msm_dp_display->pdev->dev); >> >> -- >> 2.43.0 >> >