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Wed, 20 Apr 2022 01:05:40 -0700 (PDT) Received: from [192.168.1.100] ([159.226.95.33]) by smtp.gmail.com with ESMTPSA id z1-20020a17090a014100b001d2eb7fe951sm3339335pje.13.2022.04.20.01.05.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Apr 2022 01:05:40 -0700 (PDT) Message-ID: <96d27d1f-55e4-578a-75e5-686362c05dcf@gmail.com> Date: Wed, 20 Apr 2022 16:05:35 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v2] drm/vc4: Fix pm_runtime_get_sync() usage Content-Language: en-US To: Maxime Ripard Cc: Emma Anholt , David Airlie , Daniel Vetter , Eric Anholt , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20220419124407.ugzl7hknsytbhrmr@houat> <20220420004949.20508-1-linmq006@gmail.com> <20220420075108.xm5ujthootlpayy2@houat> From: Miaoqian Lin In-Reply-To: <20220420075108.xm5ujthootlpayy2@houat> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/4/20 15:51, Maxime Ripard wrote: > On Wed, Apr 20, 2022 at 12:49:48AM +0000, Miaoqian Lin wrote: >> If the device is already in a runtime PM enabled state >> pm_runtime_get_sync() will return 1, so a test for negative >> value should be used to check for errors. >> >> Also, we need to call pm_runtime_put_noidle() when pm_runtime_get_sync() >> fails, so use pm_runtime_resume_and_get() instead. this function >> will handle this. >> >> Fixes: 4078f5757144 ("drm/vc4: Add DSI driver") >> Signed-off-by: Miaoqian Lin >> --- >> change in v2: >> - switch to pm_runtime_resume_and_get() to fix refcount leak. >> --- >> drivers/gpu/drm/vc4/vc4_dsi.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c >> index 752f921735c6..9d7ffaf6bc70 100644 >> --- a/drivers/gpu/drm/vc4/vc4_dsi.c >> +++ b/drivers/gpu/drm/vc4/vc4_dsi.c >> @@ -846,8 +846,8 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder) >> unsigned long phy_clock; >> int ret; >> >> - ret = pm_runtime_get_sync(dev); >> - if (ret) { >> + ret = pm_runtime_resume_and_get(dev); >> + if (ret < 0) { > pm_runtime_resume_and_get will return 0 on success, so the previous check was correct previous check is for pm_runtime_get_sync() not for pm_runtime_resume_and_get (), I switch to pm_runtime_resume_and_get() to fix the refcount leak bug at the same time. Sure it's ok to use check if(ret) to check the retval, I just follow a more common way for usage of pm_runtime_resume_and_get() in the codebase—— check ret<0 Since pm_runtime_resume_and_get() return negative error code. > Maxime