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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF29EC433F5 for ; Fri, 8 Apr 2022 11:52:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235150AbiDHLys (ORCPT ); Fri, 8 Apr 2022 07:54:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232866AbiDHLym (ORCPT ); Fri, 8 Apr 2022 07:54:42 -0400 Received: from mail-qk1-x72f.google.com (mail-qk1-x72f.google.com [IPv6:2607:f8b0:4864:20::72f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 017A362CA for ; Fri, 8 Apr 2022 04:52:39 -0700 (PDT) Received: by mail-qk1-x72f.google.com with SMTP id s4so4543636qkh.0 for ; Fri, 08 Apr 2022 04:52:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Jx6/Lgbitqz5l2vaW1Kah0wGVIvKoz5skxFr6Jlav/w=; b=S++XNMlvf3Vbg3Rih1bTFb/lLZQdn7EPa8DKSd1j6649HfU0cdQo29mEKO/CM1UKZm PASfkvYlTmczerTPeFCsnWQhsCz17nJ06x4kVN6JCl6sCIEOfC2CUg0hiZPc/AQ4Ln4t 7W2rglnBywYnttvathHjgcJhn0UzVdsnGI1vr/VO9rZUsvLXxK+1hPIkGbS8BR+IWSn+ IggrY86KAq9S9cEWy5t8J4iTDfPtYX/1+TilDScxqfwi886SS9VDp8q3ITUyiUTUC2Ah CRtJb2ekFG8s6seSnbe3BfEhhW7KuH35uo1ioN1V8UdWV0NKkZ9MpIxqsfW4X+F1vdHv h8dw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Jx6/Lgbitqz5l2vaW1Kah0wGVIvKoz5skxFr6Jlav/w=; b=QEb+1Nr/VmtWlQwsI6cORI78Xv9wo16eSWiTPIsEFDKmhwgcJiRe2K8YrvEkPxyauj l7CDV/OFQc5kRaKIljxkenaKYzcDzQTq7IS8KBj7cRg2Cq/ETLPspYGoPKgOqN4ZTcAk l65Et7rINWtbdTd8W53f6s3wSjOcQYMpwHlf7tdXL0BDpIYdzGfv1ixxBhaTZrKjX4Tv 99aoss0KHt4OTvvgc2YP1xuqPLVfpWboc2alBzVP9gTPX2rBmFVKKtVD0WmGDpJ5rQaA ZZtDefThjsDBAtaOMj7AdYoSuKlu+s+HNdAXRzhYXE+z8EKnfEY1V72fQxL1AL0OR8FU ASjA== X-Gm-Message-State: AOAM5331S+Aka7BG4+FYjcJd8FSyOwof3YRPEJbKD3nMwVLsl5ye58Ld zhbJjJM+7zpVgnBQ68hXyVg2rXpDKZhafmHvpmyezw== X-Google-Smtp-Source: ABdhPJzUx8+jelie1GKF76E3MKGQcEpF3pUQ1g+FajnC79YKu7g3Y5icMIcl67VWS851AmyeK0Edv1CTDuLA810H2Ic= X-Received: by 2002:a05:620a:2449:b0:69a:4ae:85e5 with SMTP id h9-20020a05620a244900b0069a04ae85e5mr4876649qkn.30.1649418758129; Fri, 08 Apr 2022 04:52:38 -0700 (PDT) MIME-Version: 1.0 References: <1649350286-11504-1-git-send-email-quic_khsieh@quicinc.com> In-Reply-To: <1649350286-11504-1-git-send-email-quic_khsieh@quicinc.com> From: Dmitry Baryshkov Date: Fri, 8 Apr 2022 14:52:27 +0300 Message-ID: Subject: Re: [PATCH] drm/msm/dp: add fail safe mode outside of event_mutex context To: Kuogee Hsieh Cc: robdclark@gmail.com, sean@poorly.run, swboyd@chromium.org, vkoul@kernel.org, daniel@ffwll.ch, airlied@linux.ie, agross@kernel.org, bjorn.andersson@linaro.org, quic_abhinavk@quicinc.com, quic_aravindh@quicinc.com, quic_sbillaka@quicinc.com, freedreno@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 7 Apr 2022 at 19:51, Kuogee Hsieh wrote: > > There is possible circular locking dependency detected on event_mutex. > To break this possible circular locking, this patch move setting fail > safe mode out of event_mutex scope. Please provide the lockdep trace here, it might help other people trying to fix the issue or working on backports to stable kernels. > > Fixes: d4aca422539c ("drm/msm/dp: always add fail-safe mode into connector mode list") > Signed-off-by: Kuogee Hsieh > --- > drivers/gpu/drm/msm/dp/dp_display.c | 6 ++++++ > drivers/gpu/drm/msm/dp/dp_panel.c | 20 ++++++++++---------- > drivers/gpu/drm/msm/dp/dp_panel.h | 1 + > 3 files changed, 17 insertions(+), 10 deletions(-) > > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c > index 178b774..a42732b 100644 > --- a/drivers/gpu/drm/msm/dp/dp_display.c > +++ b/drivers/gpu/drm/msm/dp/dp_display.c > @@ -580,6 +580,12 @@ static int dp_hpd_plug_handle(struct dp_display_private *dp, u32 data) > dp->dp_display.connector_type, state); > mutex_unlock(&dp->event_mutex); > > + /* > + * add fail safe mode outside event_mutex scope > + * to avoid potiential circular lock with drm thread > + */ > + dp_panel_add_fail_safe_mode(dp->dp_display.connector); > + > /* uevent will complete connection part */ > return 0; > }; > diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c > index f141872..26c3653 100644 > --- a/drivers/gpu/drm/msm/dp/dp_panel.c > +++ b/drivers/gpu/drm/msm/dp/dp_panel.c > @@ -151,6 +151,15 @@ static int dp_panel_update_modes(struct drm_connector *connector, > return rc; > } > > +void dp_panel_add_fail_safe_mode(struct drm_connector *connector) > +{ > + /* fail safe edid */ > + mutex_lock(&connector->dev->mode_config.mutex); > + if (drm_add_modes_noedid(connector, 640, 480)) > + drm_set_preferred_mode(connector, 640, 480); > + mutex_unlock(&connector->dev->mode_config.mutex); > +} > + > int dp_panel_read_sink_caps(struct dp_panel *dp_panel, > struct drm_connector *connector) > { > @@ -207,16 +216,7 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel, > goto end; > } > > - /* fail safe edid */ > - mutex_lock(&connector->dev->mode_config.mutex); > - if (drm_add_modes_noedid(connector, 640, 480)) > - drm_set_preferred_mode(connector, 640, 480); > - mutex_unlock(&connector->dev->mode_config.mutex); > - } else { > - /* always add fail-safe mode as backup mode */ > - mutex_lock(&connector->dev->mode_config.mutex); > - drm_add_modes_noedid(connector, 640, 480); > - mutex_unlock(&connector->dev->mode_config.mutex); > + dp_panel_add_fail_safe_mode(connector); > } > > if (panel->aux_cfg_update_done) { > diff --git a/drivers/gpu/drm/msm/dp/dp_panel.h b/drivers/gpu/drm/msm/dp/dp_panel.h > index 9023e5b..99739ea 100644 > --- a/drivers/gpu/drm/msm/dp/dp_panel.h > +++ b/drivers/gpu/drm/msm/dp/dp_panel.h > @@ -59,6 +59,7 @@ int dp_panel_init_panel_info(struct dp_panel *dp_panel); > int dp_panel_deinit(struct dp_panel *dp_panel); > int dp_panel_timing_cfg(struct dp_panel *dp_panel); > void dp_panel_dump_regs(struct dp_panel *dp_panel); > +void dp_panel_add_fail_safe_mode(struct drm_connector *connector); > int dp_panel_read_sink_caps(struct dp_panel *dp_panel, > struct drm_connector *connector); > u32 dp_panel_get_mode_bpp(struct dp_panel *dp_panel, u32 mode_max_bpp, > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project > -- With best wishes Dmitry