From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4FC7DC5B572 for ; Mon, 17 Aug 2026 08:02:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=45ngM9HYkDjlOXEkj51EXEyna6RLJFPQbYPhzWvixbI=; b=iQvdjtdlYG/o3X lqeBAWHPpRciEyr5A7wLFTbLdzZwI/5ty9c5kGMJmCUCOEcliknw5YkO19FTH6Voi/8lIUSGmWzZ+ brR26IyDHrV5YnUxuOH2JfhxCq70gOEhKMgS3/OtGkr1PWJhUnwao2JBpoIGPiufP+JUjDN3ULmBM ZE6JYS3+b6276i0er+IfvWjXqI/n3n84aa+5cQclzh+KFgYh6zGND0m7aiWNTkQahR46lD5bq0dMp HSgpewDkwj4u6mFYQKJWMiNWy4LNuX+SRTq44lzFtIsPpXbQn06p+Jj5LcVPGIPavZ5HXXG/o3/vB edGJ8zrbmvpjvIj7L6jg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wvsIL-00000005cJu-3kbw; Mon, 17 Aug 2026 08:02:09 +0000 Received: from mx0a-0031df01.pphosted.com ([205.220.168.131]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wvsIJ-00000005cI2-1rGD for linux-amlogic@lists.infradead.org; Mon, 17 Aug 2026 08:02:08 +0000 Received: from pps.filterd (m0279862.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 67H7sovs1297230 for ; Mon, 17 Aug 2026 08:02:07 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qualcomm.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= EfLblXrI2Wp6ZlzzoorT7wBL5Mi+F/9m9+D7Kvm7TA4=; b=M4gF4Is06pSxY56K W3KOFtNM5HsHAYjpCFDzpoJ8wMRVNUAmT2p7b3Ribex5cvyTG+ubAFfuKJNMPV1N AyyWnFu09qGPCbxSLwSBLZTZmiSPOsuxNXRLNAvvWPdtlSTi+IjWVy3VWYIXPwfQ s3cgXIHPxH9ppMlXGOgudH0+gUzaTEJ4lrdVj66mpLEk6/AKr8zucnJmH9YvsVXb jYf3fYfEroD61AVJdHht0op+O4V7Rmybt3iBm+z8g82NNK6C8rQdJg+Txf+5jWUF TEsLJfeveNsl4UAdW2TQSAe3iGzW257Tk8eRvYFsWO8q2Aoso5mtZsqenJy9NGP+ 2WXRtQ== Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 4g3xb1g0us-1 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT) for ; Mon, 17 Aug 2026 08:02:06 +0000 (GMT) Received: by mail-qt1-f200.google.com with SMTP id d75a77b69052e-52d91cc174aso46266931cf.2 for ; Mon, 17 Aug 2026 01:02:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oss.qualcomm.com; s=google; t=1786953726; x=1787558526; darn=lists.infradead.org; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to :content-type; bh=EfLblXrI2Wp6ZlzzoorT7wBL5Mi+F/9m9+D7Kvm7TA4=; b=aMvMUCQiES7SkAQ2aXK9qUHYz+Xr4w2qvlsAa2PmjqhbCoS0uESKbTCVO8LiFk6iNh V4DxuJCDe9ThpRppAn+6DQgIfYaO9x3qnVzGyWNi2yz41tgQDw1cMw32jOlKqgXZrvOL hcjsDYnwLF177qe44KgjQ8Z3kEtucTQsSa43FuLj6aSwTVPr95OF4f+PGm1yfpMdTjaV qqhPlAVs2z2a5gqKUg3yLzCfcljdpNFZmw7cqS0ofOx+pjvbvC6eSFIqs5b2ZuGj9pWv 2ZKNgkNzIFz+MIN8gzWptHuzuYt24o8b3znN4HlNfgvKGYTflUNR7KoEJFfCBV0XXiMa 0Wcw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786953726; x=1787558526; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=EfLblXrI2Wp6ZlzzoorT7wBL5Mi+F/9m9+D7Kvm7TA4=; b=e6D36Nk2xXqSrBWjOzLUIpt4+IdQ9j6SwVILB01Nie5Wtrqg9SnLRf4ezehUp/oKDG gCOFpzdarArplL0BsUshppr4gOdv9ZwzayMutNM7Swei5Y+MJVb133CGZpLoyREZXCy4 YS3RXd5Tsl+7hg8D9vHiRnOuLGZMLQQauXjphyzmFFPsNP6sTkRYemeSjtMZH7YT1dWq SOfbInXvaxfuhNlVEfZnTxqPIR3nTyalhB14Y75R3kPH/TdtnlZr6FCNu6AfyIH+Bw7b eyvgpH+CzrgBvMTbG/GkPWLbBh0WrwHyKb8pbv3XwK07HkQO346UhBjG8c/5Vg2geFBh 3WGg== X-Forwarded-Encrypted: i=1; AHgh+Rq9QgyK0Pr+sbJCQeTp8D324bPBh9rqyhzVto+UQDBX3PugB4XOoCLPIYLkUHubZ9CEx8o+SsxmlDsxGYI1@lists.infradead.org X-Gm-Message-State: AOJu0YyHZSkhYNt4sPIXkmjbBjQwXZGrwFJ9UU3tfJoUwOHXrFvFKmpt J2TzRedV32AWbILWmz/pjOpW2wZxpFPYyjYvtdqsTOMrbnnK5T3WdrZyRpxOSBrygWp+T6ELTo7 y+a7MjTMZf0WFjTpzrHX6hUEuyfajbMF9zQEIPxSzsHENdW+nSvkX0GiHmPDEIn+LcXw1AZ14Ig == X-Gm-Gg: AR+sD10HpXvJRKIt2NIIcapCSx1MRQa+qgotpQxs27GNIxx8R6FmTFhGl1PZriQ/QIn TkRe+T26jJ3k6HO0AuzKS6LbnOnv7BiVUrknyTcMvQSo4INR0P/Amxf+ckU17ZK1SRITYNtAInL jiYMbOgwt0orA7S0O0xS8cBXf+9f5Tjd5lnmf2z50a+tmfO34/+20GRm0sAzggEVAqYep4bgd/2 ZNazfAtxa7gpGmj3eVAhRLQTPVK3Vsp50Iy5wG4mh5mJ4K7/F/GKhQ/ktFKqs3fVLJsADQydX1H FZYum1ZREv0Ro/BMXA0CB17D5ju+O1z/hZN9Aaf/szZ7ptE1wWPypVMZK6xSUPYkl1P1EyEOPce y0mBZCz3/WHRqiuEeM7tCmGQbc4V8uUebP6YWe8UhcWL2DfAAHKb1O2EnYtkl3G1QHA== X-Received: by 2002:a05:622a:1488:b0:52b:4f1a:5fde with SMTP id d75a77b69052e-52d85380e96mr249901221cf.19.1786953725757; Mon, 17 Aug 2026 01:02:05 -0700 (PDT) X-Received: by 2002:a05:622a:1488:b0:52b:4f1a:5fde with SMTP id d75a77b69052e-52d85380e96mr249900321cf.19.1786953725258; Mon, 17 Aug 2026 01:02:05 -0700 (PDT) Received: from [10.111.162.109] (Global_NAT1_IAD_FW.qualcomm.com. [129.46.232.65]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-52db612c2bfsm8319271cf.11.2026.08.17.01.01.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Aug 2026 01:02:04 -0700 (PDT) Message-ID: Date: Mon, 17 Aug 2026 16:01:41 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/5] drm/bridge: allow hpd_notify() to suppress connector hotplug events 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-v1-1-646a10256233@oss.qualcomm.com> Content-Language: en-US From: Yongxing Mou In-Reply-To: X-Authority-Analysis: v=2.4 cv=Ua9hjqSN c=1 sm=1 tr=0 ts=6a82bffe cx=c_pps a=JbAStetqSzwMeJznSMzCyw==:117 a=C3Dk8TwHQYyIj7nOf9RCJw==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_K5XuSEh1TEqbUxoQ0s3:22 a=EUspDBNiAAAA:8 a=EPiK6WrKEJDDbvHRsiMA:9 a=QEXdDO2ut3YA:10 a=uxP6HrT_eTzRwkO_Te1X:22 X-Proofpoint-GUID: YO8JDMrb_PUIBkhgIVbHAKK_DrfMJoLH X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE3MDA1OSBTYWx0ZWRfXwrbSnXgicJGf gfeetjFH3Gg0AETSHPnxjZuhwEbSvZfIDIVLEoOhotcWfVtHO7t2rFEj58N4LY2J2UNy45Ir2Dw NSlTUo2jxVmtmUQxoEctGWDrROCtB1oA7/zidiLgPAQeqvqX8IieB3FMcybn3pQqkiBhf+IHAYK ThNxqtXsDYsIOMua1lq++vzSh4AWnBtmLmorx8IIcP2h5oCHtJyhFwV1E1A9pPqjQq64iNuRgyo 0jFV3ZamGQ+WmmfmWYqHtfTGkOCH5YfJP2npQelhO4dYXuIa8tLUyqAmhbPjO68cvvhTOo9s/KI oXaXGc37RHVUuB3GZdwipWfONPuUlMXN0Gg3IxG3AVL+MAfShvCcWJ8sxsTILWZE9uYikkiiv5n lOkWpMM83iOAjvO0v56CcqvugcOzuWjtRCHZVJQMWXhbb89zi8cY0ISfpqYw/eXqeJpfsxWCXof kgWVEmjOKBXabAJGSsg== X-Proofpoint-Spam-Info: AW1haW4tMjYwODE3MDA1OSBTYWx0ZWRfXy+IxcOs5Ke/H sGCbp2E3kd5403VCs1P+XmRLOS2AAEceTXqhk1nNPAFDR6eX3rQM3rFww6xeTNlQ8sbCOGwHTWs LJecg7GKT4Ypa7JWwIbNajAOgXlHYuI= X-Proofpoint-ORIG-GUID: YO8JDMrb_PUIBkhgIVbHAKK_DrfMJoLH 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 spamscore=0 adultscore=0 priorityscore=1501 malwarescore=0 suspectscore=0 impostorscore=0 bulkscore=0 lowpriorityscore=0 phishscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608170059 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260817_010207_504937_21DD27F7 X-CRM114-Status: GOOD ( 21.03 ) 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On 7/12/2026 6:21 PM, Dmitry Baryshkov wrote: > On Mon, Jun 29, 2026 at 10:48:03PM +0800, Yongxing Mou wrote: >> The bridge connector framework currently invokes all bridge >> hpd_notify() callbacks and unconditionally emits a connector hotplug >> event afterwards. >> >> However, not every HPD notification requires a userspace hotplug event. >> >> In particular, DP MST bridges may use hpd_notify() to propagate HPD and >> IRQ notifications through the bridge chain while the actual hotplug >> handling is performed by the DRM DP MST core. Connector creation, >> removal and userspace hotplug events are already managed by the MST >> topology framework. >> >> Allow hpd_notify() implementations to suppress the bridge connector >> hotplug event by introducing a bool *send_hotplug parameter. Drivers >> can clear this flag when HPD processing should not result in a >> connector hotplug notification. > > Why? Worst case the kernel receives another hotplug notification which > gets ignored by the driver. > Hi, thanks for reviwing those patches. Let me try to explain the motivation. Semantically, IRQ_HPD is just an IRQ notification, not a connection state transition, and shouldn't be turned into a userspace hotplug in the first place. However, drm_bridge_connector_handle_hpd() currently calls drm_kms_helper_connector_hotplug_event() unconditionally after processing the event, so every IRQ_HPD ends up reported as a hotplug. Second, MST IRQ_HPD is level-sticky -- as long as the ACK has not been cleared, the IRQ keeps firing repeatedly, and MST bring-up (link training / MST enable handshake) itself generates a burst of IRQ_HPDs. So this is not about "one extra hotplug", but about a burst of them within a short window. Every one of those hotplugs is delivered to userspace via udev and prompts the compositor to re-probe the connector. In the window before mst_active is set, that re-probe walks back into msm_dp_bridge_detect() and performs aux/DPCD accesses, racing with the MST enable flow. The amplification also isn't limited to a single connector: on Hamoa there are 4 connectors (3x DP + eDP), and we observe that a hotplug on any one connector causes the compositor to re-query all 4. So this burst of spurious IRQ_HPDs during MST enable ends up amplified across the whole card. >> >> A NULL pointer indicates that hotplug suppression is not supported by >> the caller, such as the connector detect polling path. > > And nothing in this patch makes any use of it. I'd say, it's > questionable addition. Let me check other patches... > You are right, I will reorganize the patches in next patchset. >> >> Signed-off-by: Yongxing Mou >> --- >> drivers/gpu/drm/bridge/lontium-lt9611uxc.c | 3 ++- >> drivers/gpu/drm/display/drm_bridge_connector.c | 15 +++++++++------ >> drivers/gpu/drm/meson/meson_encoder_hdmi.c | 3 ++- >> drivers/gpu/drm/msm/dp/dp_display.c | 3 ++- >> drivers/gpu/drm/msm/dp/dp_drm.h | 3 ++- >> drivers/gpu/drm/omapdrm/dss/hdmi4.c | 3 ++- >> include/drm/drm_bridge.h | 3 ++- >> 7 files changed, 21 insertions(+), 12 deletions(-) > _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic