From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowjanya Komatineni Subject: Re: [RFC PATCH v1 3/5] media: tegra-video: Move PM runtime handle to streaming Date: Tue, 28 Apr 2020 08:22:02 -0700 Message-ID: <5741d5d3-e474-e23c-4841-809df5760067@nvidia.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Language: en-US Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Dmitry Osipenko , thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, frankc-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org Cc: linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org On 4/28/20 8:15 AM, Dmitry Osipenko wrote: > External email: Use caution opening links or attachments > > > 28.04.2020 18:08, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> 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 =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>> 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 =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>>>> 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_subde= v >>>>>> *subdev, int enable) >>>>>> struct tegra_vi_channel *chan =3D >>>>>> v4l2_get_subdev_hostdata(subdev); >>>>>> struct tegra_csi_channel *csi_chan =3D to_csi_chan(subdev); >>>>>> struct tegra_csi *csi =3D csi_chan->csi; >>>>>> + int ret; >>>>>> + >>>>>> + if (enable && atomic_add_return(1, &csi->clk_refcnt) =3D=3D 1)= { >>>>>> + ret =3D 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. pm_runtime_get_sync() increments power.usage_count prior to rpm_resume if rpm_resume fails it does not decrement usage_count. So to balance count on failure, calling pm_runtime_put_noidle() > >>>>>> + atomic_dec(&csi->clk_refcnt); >>>>>> + return ret; >>>>>> + } >>>>>> + } >>>>>> + >>>>>> + ret =3D csi->ops->csi_streaming(csi_chan, chan->pg_mode, enabl= e); >>>>>> >>>>>> - 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 othe= r >>>> 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/runti= me.c#L1079 Got it. Will remove refcount for RPM put/get