From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowjanya Komatineni Subject: Re: [RFC PATCH v7 6/9] media: tegra: Add Tegra210 Video input driver Date: Wed, 15 Apr 2020 10:21:15 -0700 Message-ID: <6afa951e-d904-f3c0-053f-82a02fb18979@nvidia.com> References: <1586919463-30542-1-git-send-email-skomatineni@nvidia.com> <1586919463-30542-7-git-send-email-skomatineni@nvidia.com> <4118112f-f865-5460-6319-d71271fd78d1@gmail.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-clk-owner@vger.kernel.org To: Dmitry Osipenko , thierry.reding@gmail.com, jonathanh@nvidia.com, frankc@nvidia.com, hverkuil@xs4all.nl, sakari.ailus@iki.fi, helen.koike@collabora.com Cc: sboyd@kernel.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-tegra@vger.kernel.org On 4/15/20 9:54 AM, Sowjanya Komatineni wrote: > > On 4/15/20 7:22 AM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 15.04.2020 05:57, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>> +static int tegra_csi_remove(struct platform_device *pdev) >>> +{ >>> +=C2=A0=C2=A0=C2=A0=C2=A0 struct tegra_csi *csi =3D platform_get_drvdat= a(pdev); >>> +=C2=A0=C2=A0=C2=A0=C2=A0 int err; >>> + >>> +=C2=A0=C2=A0=C2=A0=C2=A0 err =3D host1x_client_unregister(&csi->client= ); >>> +=C2=A0=C2=A0=C2=A0=C2=A0 if (err < 0) { >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0 dev_err(csi->dev, >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "failed to unregister h= ost1x client: %d\n", err); >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0 return err; >>> +=C2=A0=C2=A0=C2=A0=C2=A0 } >>> + >>> +=C2=A0=C2=A0=C2=A0=C2=A0 pm_runtime_disable(csi->dev); >>> +=C2=A0=C2=A0=C2=A0=C2=A0 kfree(csi); >> IIRC, the driver removal is invoked on the unbinding. Hence, I'm not >> sure how moving away from the resource-managed API helps here. Could you >> please explain in a more details? >> >> Have you tried to test this driver under KASAN? I suspect that you just >> masked the problem, instead of fixing it. > Using devm_kzalloc for vi/csi structures based on prior feedback=20 > request to switch to use kzalloc all over this driver. > > Hi Hans, > > video devices lifetime is till video device nodes are released. So,=20 > v4l2 device release callback does the release of tegra channel=20 > allocation which hold video device. > > Below are the 3 possible cases of unbind/unload, > > 1. during tegra-video module unload, if v4l2 device refcnt is not 0=20 > which is the case when any of video device node handle is kept opened=20 > then unloading module will not happen and module refcnt is also=20 > non-zero and unloading tegra-video module reports module in use. > > 2. during tegra-video driver unbind, tegra-video driver removal will=20 > do vi/csi clients exit ops which unregisters video device allocated=20 > memory during release callback of v4l2 device. vi/csi structure=20 > allocation remains same as vi/csi driver removal will not happen in=20 > this case. > > > 3. during direct host1x client drivers vi/csi unbind, both=20 > host1x_clients vi/csi gets unregistered, deletes host1x logical device=20 > which executes tegra-video driver removal() -> vi/csi exit() before=20 > vi/csi memory gets freed in vi/csi driver remove(). > > So, any active streaming will stop and video devices are unregistered=20 > during direct client driver unbind prior to freeing vi/csi memory. > > Also vi/csi driver remove does explicit free vi/csi as its allocated=20 > with kzalloc. So not sure how using kzalloc is different to=20 > devm_kzalloc for vi/csi structure in terms of when vi/csi memory gets=20 > freed? > > Except for channel allocation which holds video device and as video=20 > device life time is beyond tegra-video module unbind->vi exit(), looks=20 > like we can use devm_kzalloc for vi/csi. > > > Can you please comment if you still think we need to use kzalloc=20 > rather than devm_kzalloc for vi/csi structure allocation? > > Thanks > > Sowjanya > One more case is when video device node is kept opened with v4l2-ctl=20 sleep (rather than streaming), where it will keep device node open for=20 specified time and if direct vi client driver unbind happens then vi=20 driver remove() will free vi memory before v4l2 device release happens. But I don't see any crash or errors with this case. Also if we allow direct client driver unbind, then vi structure memory=20 lifetime should also be till v4l2 device release happens. But we can free vi in v4l2 device release callback as in case when=20 device node is not kept opened, video device release happens immediate=20 and we cant free vi that early. Hans/Thierry, Can you please comment on this case? Thanks Sowjanya