From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy for a long time Date: Wed, 29 Apr 2020 18:24:34 +0200 Message-ID: <20200429162434.GA3157354@ulmo> References: <20200427110033.GC3464906@ulmo> <3a06811c-02dc-ce72-ebef-78c3fc3f4f7c@gmail.com> <20200427151234.GE3464906@ulmo> <1ab276cf-c2b0-e085-49d8-b8ce3dba8fbe@gmail.com> <20200429081448.GA2345465@ulmo> <20200429085502.GB2345465@ulmo> <9e36c4ec-ca02-bd15-d765-15635f09db4b@gmail.com> <7442f4cd-6406-41f6-5c9b-932bff8ad5b2@nvidia.com> <5863e364-480e-7839-c42b-73a7f6990a30@gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="HcAYCG3uE/tztfnV" Return-path: Content-Disposition: inline In-Reply-To: <5863e364-480e-7839-c42b-73a7f6990a30-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Dmitry Osipenko Cc: Jon Hunter , Wolfram Sang , Laxman Dewangan , Manikanta Maddireddy , Vidya Sagar , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org --HcAYCG3uE/tztfnV Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 29, 2020 at 05:46:46PM +0300, Dmitry Osipenko wrote: > 29.04.2020 16:57, Jon Hunter =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >=20 > > On 29/04/2020 13:35, Dmitry Osipenko wrote: > >> 29.04.2020 11:55, Thierry Reding =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >> ... > >>>>> It's not "papering over an issue". The bug can't be fixed properly > >>>>> without introducing I2C atomic transfers support for a late suspend > >>>>> phase, I don't see any other solutions for now. Stable kernels do n= ot > >>>>> support atomic transfers at all, that proper solution won't be back= portable. > >>>> > >>>> Hm... on a hunch I tried something and, lo and behold, it worked. I = can > >>>> get Cardhu to properly suspend/resume on top of v5.7-rc3 with the > >>>> following sequence: > >>>> > >>>> revert 9f42de8d4ec2 i2c: tegra: Fix suspending in active runtime PM= state > >>>> apply http://patchwork.ozlabs.org/project/linux-tegra/patch/2019121= 3134417.222720-1-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org/ > >>>> > >>>> I also ran that through our test farm and I don't see any other issu= es. > >>>> At the time I was already skeptical about pm_runtime_force_suspend()= and > >>>> pm_runtime_force_resume() and while I'm not fully certain why exactl= y it > >>>> doesn't work, the above on top of v5.7-rc3 seems like a good option. > >>>> > >>>> I'll try to do some digging if I can find out why exactly force susp= end > >>>> and resume doesn't work. > >>> > >>> Ah... so it looks like pm_runtime_force_resume() never actually does > >>> anything in this case and then disable_depth remains at 1 and the fir= st > >>> tegra_i2c_xfer() will then fail to runtime resume the controller. > >> > >> That's the exactly expected behaviour of the RPM force suspend/resume. > >> The only unexpected part for me is that the tegra_i2c_xfer() runtime > >> resume then fails in the NOIRQ phase. > >=20 > > From reading the changelog for commit 1e2ef05bb8cf ("PM: Limit race > > conditions between runtime PM and system sleep (v2))", this is the > > expected behaviour for runtime resume in the noirq phase. >=20 > I'm curious whether there is a way to tell RPM that it's okay to do it > for a particular device, like I2C that uses IRQ-safe RPM + doesn't have > parent devices that need to be resumed. Been there, done that: http://patchwork.ozlabs.org/project/linux-tegra/patch/20191128160314.23812= 49-2-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org/ Thierry --HcAYCG3uE/tztfnV Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAl6pqj8ACgkQ3SOs138+ s6FufxAAljOq+NRIHB/PrCysp40r4qVToNmFmuf2zWVsbHpiIlzuZ+F7+QcgkgTt Myj7pH0g9k+7Xo/Od6aHpoA3ZaYeP2TzpTWii79LwzphTMOa88bzggP0W6td7WO4 f1NINRTRi8VN6yC55OqJB+6Og/3IemmEENmCR0HuiRTBI9Di8rJD0sA1dKH81emy pf0y/Sct2xkplpGoePczuhOgWZkikqubTRtFjcri7ISzANEMWUc3Sopb//UZ4C/t tpgGUT4TDD1EwLlt4HEGKEKfVn++nmxp7MKcF2kK7g6AmryrxIACq6kcsZPWhjZZ Zz/fxxrsyKucAWfOsr+cvCU97IP+xhFOQqb/q1yygmLu9hgtFBrgg8+N5+NCdVBN lMJYDTsXTrLa/2Px0N51hK1uvlKFiBEll+Ae5COoDb8Qokbxzx0+7ArumgOM/Iq6 kAmvEFKoGNCUovcMzpNAEXU+nPst1rGlbJ0Nbl651mc7JWzKZrVaOU/G63ykm5TG lwkRJ7UmLzc4V+NQsB4WXVZ3tvKPf3bjYTY9tbnKxvQ3RKwRPS7tZB5ZXAsfPH4v UAvcuKezK0AjRBjm7R74zhpd+lbzzcRm5YofPkLsVefYri53c/HNOTiICxPZPzwl HvfrJcVGjDt4r2nSd2qxO451DAU3EflwafxVvSetF51T5GBq8LQ= =rzYl -----END PGP SIGNATURE----- --HcAYCG3uE/tztfnV--