From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751549AbdBYBlX (ORCPT ); Fri, 24 Feb 2017 20:41:23 -0500 Received: from szxga03-in.huawei.com ([45.249.212.189]:2968 "EHLO dggrg03-dlp.huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751424AbdBYBlW (ORCPT ); Fri, 24 Feb 2017 20:41:22 -0500 Subject: Re: [RFC][PATCH v2] drm: kirin: Add a mutex to avoid fb initialization race To: John Stultz , lkml References: <1487985916-29450-1-git-send-email-john.stultz@linaro.org> CC: Rongrong Zou , Xinwei Kong , Chen Feng , "David Airlie" , Daniel Vetter , Sean Paul , From: liuxinliang Message-ID: <58B0E044.6010905@hisilicon.com> Date: Sat, 25 Feb 2017 09:39:16 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <1487985916-29450-1-git-send-email-john.stultz@linaro.org> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.46.44.48] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A090202.58B0E03D.0062,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 825e6a91f3c10da18ec7647905d220d1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi John, The patch seems good to me, except one minus comment. Maybe change fb_lock to fbdev_lock would be better. Thanks, -xinliang On 2017/2/25 9:25, John Stultz wrote: > In some cases I've been seeing a race where two framebuffers > would be initialized, as kirin_fbdev_output_poll_changed() > might get called quickly in succession, resulting in the > initialization happening twice. This could cause the system > to boot up with a blank screen. > > This patch adds a simple mutex to serialize it and seems to > avoid the race. > > Suggestions or feedback would be greatly appreciated! > > Cc: Xinliang Liu > Cc: Rongrong Zou > Cc: Xinwei Kong > Cc: Chen Feng > Cc: David Airlie > Cc: Daniel Vetter > Cc: Sean Paul > Cc: dri-devel@lists.freedesktop.org > Signed-off-by: John Stultz > --- > drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c | 4 ++++ > drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h | 1 + > 2 files changed, 5 insertions(+) > > diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c > index 7ec93ae..b83556a 100644 > --- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c > +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c > @@ -55,6 +55,7 @@ static void kirin_fbdev_output_poll_changed(struct drm_device *dev) > { > struct kirin_drm_private *priv = dev->dev_private; > > + mutex_lock(&priv->fb_lock); > if (priv->fbdev) { > drm_fbdev_cma_hotplug_event(priv->fbdev); > } else { > @@ -63,6 +64,7 @@ static void kirin_fbdev_output_poll_changed(struct drm_device *dev) > if (IS_ERR(priv->fbdev)) > priv->fbdev = NULL; > } > + mutex_unlock(&priv->fb_lock); > } > #endif > > @@ -95,6 +97,8 @@ static int kirin_drm_kms_init(struct drm_device *dev) > if (!priv) > return -ENOMEM; > > + mutex_init(&priv->fb_lock); > + > dev->dev_private = priv; > dev_set_drvdata(dev->dev, dev); > > diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h > index 7f60c649..9b6d2b1 100644 > --- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h > +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h > @@ -23,6 +23,7 @@ struct kirin_drm_private { > #ifdef CONFIG_DRM_FBDEV_EMULATION > struct drm_fbdev_cma *fbdev; > #endif > + struct mutex fb_lock; > }; > > extern const struct kirin_dc_ops ade_dc_ops;