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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 E4F7DC61DD3 for ; Mon, 31 Aug 2026 09:01:26 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 1943010E772; Mon, 31 Aug 2026 09:01:26 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="ZOstk24V"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2BD1510E772 for ; Mon, 31 Aug 2026 09:01:24 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id B097643B6E; Mon, 31 Aug 2026 09:01:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B6F31F000E9; Mon, 31 Aug 2026 09:01:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788166883; bh=AsLvywh97tWoMLE1dP3LcmrqBMHLohFtKWi6BDw+w2w=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=ZOstk24VMDYiLcr1tryqBNnsxtMsOA+g468k/bTS0IhuPvtOZ2rCuSepVDQuYLzx6 EKx7T3nOcqxXbEqfP7I4DHmMmeKzxjgC1FN3M8mL9cwYmzVoJub1MqwSstx3/AbiFb PG6vFcfCGJXgtQlVEac2l97oRtMYJp5S/Z3cf8+qw5TTofIQy8TrUUcplORSpHU5cd k0zz3hSyBCGCghGV3Kr9UaoG70ktbgxD4Zi4YCUCTV3SKZ/KdZjXBI0ld/KEwAXwpl 4wp51ByAn4QfW96L3SQiB/aBiwXIIe/OSSH8mz/3+hQEtTRMJR314cATdFMm9mqugP 8B816yYtjBufQ== From: sashiko-bot@kernel.org Subject: Re: [PATCH v6 09/29] drm/msm/dp: add support to enable MST in mainlink control To: "Yongxing Mou" Cc: dri-devel@lists.freedesktop.org In-Reply-To: <20260831-msm-dp-mst-v6-9-c91d35d6fb9e@oss.qualcomm.com> References: <20260831-msm-dp-mst-v6-0-c91d35d6fb9e@oss.qualcomm.com> <20260831-msm-dp-mst-v6-9-c91d35d6fb9e@oss.qualcomm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Mon, 31 Aug 2026 09:01:22 +0000 Message-Id: <20260831090123.5B6F31F000E9@smtp.kernel.org> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: Pre-existing issues: - [High] Sleeping function msleep() is called in an atomic commit context v= ia msm_dp_ctrl_mst_send_act(). -- commit 10a0de5e53b18299bcdd23065b77d3e1f1d02df3 Author: Abhinav Kumar drm/msm/dp: add support to enable MST in mainlink control This commit adds support to program the MST enable bit in the mainlink cont= rol=20 register when an MST session is active or being disabled. > diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp= _ctrl.c > index 65d22505c2b67..cd6ae0d5372c9 100644 > --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c > +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c > @@ -276,6 +276,19 @@ int msm_dp_ctrl_mst_send_act(struct msm_dp_ctrl *msm= _dp_ctrl, [Severity: High] This isn't a bug introduced by this patch, but it is a pre-existing High severity issue that persists through the end of the series. Does this code call a sleeping function from an atomic context? Looking at msm_dp_ctrl_mst_send_act(), it executes a sleeping delay: int msm_dp_ctrl_mst_send_act(...) { ... msleep(frame_time_ms); ... } Calling a sleeping function like msleep() from an atomic context causes ker= nel warnings (might_sleep()), system instability, and potential deadlocks on hot paths. This appears to be triggered on an atomic commit path: msm_dp_display_atomic_enable() (an encoder/bridge atomic enable callback) calls msm_dp_display_enable(), which calls msm_dp_ctrl_on_stream(), which in turn calls msm_dp_ctrl_mst_send_act(). A similar path exists during disable: msm_dp_display_atomic_disable() -> msm_dp_ctrl_mst_send_act(). The DRM Subsystem Details explicitly define encoder atomic enable/disable callbacks as atomic context paths where sleeping is strictly forbidden. Only non-sleeping delays (udelay, ndelay) are safe. Checking the final state of the series (commit 48ec7f7903ee) confirms this = bug is not resolved later; dpu_encoder_mst_atomic_disable() still calls msm_dp_mst_stream_disable(), which reaches msm_dp_ctrl_mst_send_act() and sleeps. > return 0; > } > =20 > +static void msm_dp_ctrl_mst_config(struct msm_dp_ctrl_private *ctrl, boo= l enable) > +{ > + u32 mainlink_ctrl; > + > + mainlink_ctrl =3D msm_dp_read_link(ctrl, REG_DP_MAINLINK_CTRL); > + if (enable) > + mainlink_ctrl |=3D DP_MAINLINK_CTRL_MST_EN; > + else > + mainlink_ctrl &=3D ~DP_MAINLINK_CTRL_MST_EN; > + > + msm_dp_write_link(ctrl, REG_DP_MAINLINK_CTRL, mainlink_ctrl); > +} [ ... ] --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260831-msm-dp-mst= -v6-0-c91d35d6fb9e@oss.qualcomm.com?part=3D9