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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id u7sm14313236lfg.20.2020.04.28.08.15.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Apr 2020 08:15:39 -0700 (PDT) Subject: Re: [RFC PATCH v1 3/5] media: tegra-video: Move PM runtime handle to streaming To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, frankc@nvidia.com, hverkuil@xs4all.nl Cc: linux-media@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <1588047650-29402-1-git-send-email-skomatineni@nvidia.com> <1588047650-29402-4-git-send-email-skomatineni@nvidia.com> <631390cb-9aff-0e3f-6c39-81d6c565987e@gmail.com> <3ef69413-a606-b475-f530-d5534760b73b@nvidia.com> <2b334095-fadb-bf0a-f7a8-62fc798c2bd2@gmail.com> <18a7b095-7f0f-7819-c786-7e011cfd14ed@nvidia.com> From: Dmitry Osipenko Message-ID: Date: Tue, 28 Apr 2020 18:15:38 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <18a7b095-7f0f-7819-c786-7e011cfd14ed@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 28.04.2020 18:08, Sowjanya Komatineni пишет: > > On 4/28/20 7:59 AM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 28.04.2020 17:51, Sowjanya Komatineni пишет: >>> On 4/28/20 6:59 AM, Dmitry Osipenko wrote: >>>> External email: Use caution opening links or attachments >>>> >>>> >>>> 28.04.2020 07:20, Sowjanya Komatineni пишет: >>>>> diff --git a/drivers/staging/media/tegra-video/csi.c >>>>> b/drivers/staging/media/tegra-video/csi.c >>>>> index b3dd0c3..29ccdae 100644 >>>>> --- a/drivers/staging/media/tegra-video/csi.c >>>>> +++ b/drivers/staging/media/tegra-video/csi.c >>>>> @@ -272,8 +272,25 @@ static int tegra_csi_s_stream(struct v4l2_subdev >>>>> *subdev, int enable) >>>>>         struct tegra_vi_channel *chan = >>>>> v4l2_get_subdev_hostdata(subdev); >>>>>         struct tegra_csi_channel *csi_chan = to_csi_chan(subdev); >>>>>         struct tegra_csi *csi = csi_chan->csi; >>>>> +     int ret; >>>>> + >>>>> +     if (enable && atomic_add_return(1, &csi->clk_refcnt) == 1) { >>>>> +             ret = pm_runtime_get_sync(csi->dev); >>>>> +             if (ret < 0) { >>>>> +                     dev_err(csi->dev, >>>>> +                             "failed to get runtime PM: %d\n", ret); >>>>> +                     pm_runtime_put_noidle(csi->dev); Why this pm_runtime_put_noidle() is needed? This should be wrong, please remove it. >>>>> +                     atomic_dec(&csi->clk_refcnt); >>>>> +                     return ret; >>>>> +             } >>>>> +     } >>>>> + >>>>> +     ret = csi->ops->csi_streaming(csi_chan, chan->pg_mode, enable); >>>>> >>>>> -     return csi->ops->csi_streaming(csi_chan, chan->pg_mode, enable); >>>>> +     if ((ret < 0 || !enable) && >>>>> atomic_dec_and_test(&csi->clk_refcnt)) >>>>> +             pm_runtime_put_sync(csi->dev); >>>> Runtime PM maintains its own refcount, why these >>>> clk_refcnt/power_on_refcnt are needed? >>> Streaming is per channel and we can't turn power/clocks off while other >>> channels may still be running. >>> >> All channels use the same CSI device. You should remove the custom >> refcounting. >> >> BTW, next time you'll really need to do refcounting, use the generic >> kref. > > Before channel stream we enable power/clocks and after streaming we stop. > > So without refcount, on stream stop of any of the channel RPM put turns > power/clock but other channels will still be streaming. > Runtime PM uses its own refcounting. Please consult the RPM code and documentation. https://elixir.bootlin.com/linux/v5.7-rc3/source/include/linux/pm_runtime.h#L78 https://elixir.bootlin.com/linux/v5.7-rc3/source/drivers/base/power/runtime.c#L1079