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Thu, 22 Oct 2026 23:10:43 -0700 (PDT) Received: from [10.64.69.173] ([114.94.8.21]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ada4890bb2sm7186038a91.1.2026.10.22.23.10.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Oct 2026 23:10:42 -0700 (PDT) Message-ID: <8c0dd87d-d054-4423-a62f-ac30d34a23ca@oss.qualcomm.com> Date: Fri, 23 Oct 2026 14:10:36 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/bridge: aux-hpd-bridge: replay last HPD status on hpd_enable To: Luca Ceresoli Cc: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Dmitry Baryshkov , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20260803-drm-usbdp-preboot-v1-1-2539b362be00@oss.qualcomm.com> <179256808506.89747.16992632119493179553.b4-review@b4> Content-Language: en-US From: Yongxing Mou In-Reply-To: <179256808506.89747.16992632119493179553.b4-review@b4> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: W9lZ_zrIFjdQ8m2DskqyThaQCWBXgdxd X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIzMDAyNCBTYWx0ZWRfXxVA372fjRI9t wc89EgCIW4MqDCFrnO3MSFhfbTjqt2tphv4ut0e1Q0i2n1iSX4PlluR1BxliJu1VzlB9FAt5o7b pakIflijnZUmbVYSFmZL/ip+57DoAJA= X-Authority-Analysis: v=2.4 cv=VNZIDNPX c=1 sm=1 tr=0 ts=6adafa65 cx=c_pps a=UNFcQwm+pnOIJct1K4W+Mw==:117 a=Uz3yg00KUFJ2y2WijEJ4bw==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=Um2Pa8k9VHT-vaBCBUpS:22 a=EUspDBNiAAAA:8 a=KstRv3tEx54DabmpsY0A:9 a=QEXdDO2ut3YA:10 a=uKXjsCUrEbL0IQVhDsJ9:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIzMDAyNCBTYWx0ZWRfXyOO3BipBiBU2 nJSFwhbj5qxi0Zpx48yb4aQi8zDyvWAokFLyHDt1YeE9nEftYEiWO5Vi76xedgZOtfjlVyCrQmU 36GHP/UWM5hJW7FKDmiagYbw/nzU44IcyEQIiePCTlfB1/b/tOBOVjhzG14wIi1Wz7Yl74GKU1e ShUMv7gFLz5gowK7jV7mIChwUgz0TuJdu5awZKAMOEQ5uZMQyicoMRWqKzfCt1BKklirXhOehpb 2NcMmmWL8LpQk8DYaOc/s3+cPG/SwjVdYggQrMNNVa11NqdZw3thOgF+0um7IpQ3ZeCODuutUwZ 7dOsV2esY5OU+0yPVkkWOMOOLTC857DeyU2ykQNN8UxDfNAmp0qw9jVKM8UndvR2YcW9tjQd62q TG6xvA345Ha8YshFaNABXdN0PcBqEYrohqY+5r+yMzCFk3gIsEuxgKo2WvTVAkaAfSChajDUTe8 YuPtBjRcHX+8V7xZKwg== X-Proofpoint-ORIG-GUID: W9lZ_zrIFjdQ8m2DskqyThaQCWBXgdxd X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-23_01,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 bulkscore=0 adultscore=0 phishscore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610230024 On 10/21/2026 3:34 PM, Luca Ceresoli wrote: > Hello Yongxing, Dmitry, > >> If a downstream consumer (e.g. drm_bridge_connector attached by the >> msm/dp driver) registers its HPD callback after an upstream driver >> has already reported a HPD event through drm_aux_hpd_bridge_notify(), >> the notification is dropped because bridge->hpd_cb is still NULL. >> This can affect any user of drm_aux_hpd_bridge_notify() whose >> downstream consumer arms HPD only after upstream events have started. >> >> The race has been observed on Qualcomm X1E-based laptops during boot, >> when pmic_glink_altmode reports the initial USB-C DP connection state >> before the DP driver has finished probing and enabled HPD handling on >> the bridge. The consumer then never observes the initial connected >> state and the external display remains dark. >> >> Cache the last HPD status reported through drm_aux_hpd_bridge_notify() >> and replay it when HPD is enabled by the downstream consumer. >> >> The replay is deferred to a work item so that the replayed HPD >> notification is delivered outside drm_bridge_hpd_enable()'s call >> context. >> >> This follows the same pattern as display-connector, which also defers >> an initial HPD notification from .hpd_enable(), but reuses the cached >> status since aux-hpd-bridge cannot re-detect sink presence on its own. >> >> Fixes: e560518a6c2e ("drm/bridge: implement generic DP HPD bridge") >> Signed-off-by: Yongxing Mou > > Is this patch still current? > > It looks mostly OK at quick glance, but there are issues reported by > sashiko which look valid to me. If you could reply to those remarks, either > confirming the issue or explaining why it isn't, it would help reviewing. > Hi, thanks for reminder, will apply AI commenst later and post V2.> @Dmitry: I'm not familiar with this code, do you have any comment on this > patch? > > Luca >