Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754444AbaKXSCS (ORCPT ); Mon, 24 Nov 2014 13:02:18 -0500 Received: from mail-qg0-f45.google.com ([209.85.192.45]:55264 "EHLO mail-qg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752887AbaKXSCP (ORCPT ); Mon, 24 Nov 2014 13:02:15 -0500 Date: Mon, 24 Nov 2014 14:02:25 -0400 From: Eduardo Valentin To: Lukasz Majewski Cc: Zhang Rui , Ezequiel Garcia , Kuninori Morimoto , Linux PM list , Vincenzo Frascino , Bartlomiej Zolnierkiewicz , Lukasz Majewski , Nobuhiro Iwamatsu , Mikko Perttunen , Stephen Warren , Thierry Reding , Alexandre Courbot , linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, Viresh Kumar Subject: Re: [PATCH v2] thermal:core:fix: Check return code of the ->get_max_state() callback Message-ID: <20141124180222.GA1449@developer> References: <1415898165-27406-1-git-send-email-l.majewski@samsung.com> <1416305790-27746-1-git-send-email-l.majewski@samsung.com> <20141121180826.GA3331@developer> <20141124113854.36975fb2@amdc2363> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ZGiS0Q5IWpPtfppv" Content-Disposition: inline In-Reply-To: <20141124113854.36975fb2@amdc2363> User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ZGiS0Q5IWpPtfppv Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello Lukasz, On Mon, Nov 24, 2014 at 11:38:54AM +0100, Lukasz Majewski wrote: > Hi Eduardo, >=20 > >=20 > > Lukasz, > >=20 > > On Tue, Nov 18, 2014 at 11:16:30AM +0100, Lukasz Majewski wrote: > > > The return code from ->get_max_state() callback was not checked > > > during binding cooling device to thermal zone device. > > >=20 > > > Signed-off-by: Lukasz Majewski > > > --- > > > Changes for v2: > > > - It turned out that patches from 1 to 6 from v1 are not needed, > > > since they either already solve the problem (like imx_thermal.c) or > > > not use cpufreq as a thermal cooling device. > > > - The patch 7 from v1 is also not needed since this patch on error > > > exits this function without using max_state variable. > > > - In thermal driver probe the cpufreq_cooling_register() method > > > presence is crucial to evaluate if the thermal driver needs any > > > actions with -EPROBE_DEFER. > >=20 > > Have you tried this patch with of-thermal based systems? >=20 > Yes. I did try it with Exynos (after the rework). And there weren't > any regressions. >=20 > To be precise - do you refer to of_cpufreq_cooling_register() [1] or > cpufreq_cooling_register() [2]? >=20 [1] > For the latter [2] - drivers like imx_thermal.c are fully prepared for > -EDEFER_PROBE. >=20 > For the former [1] - only cpufreq-dt.c uses it (and Exynos SoC after > the rework). >=20 > >=20 > > The above proposal works if the thermal driver is dealing with loading > > cpu_cooling. But for of-thermal based drivers, the idea is to leave to > > cpufreq code to load it.=20 >=20 > I assume, that you mean case [1]? >=20 yup > >=20 > > As an example, I am taking the ti-soc-thermal, but we already have > > other of-thermal based drivers. Booting with this patch ti-soc-thermal > > (of-based boot) loads fine, but the cpu_cooling never gets bound to > > the thermal zone. >=20 > Could you share the exact SoC/board/_defconfig setup to reproduce this > behavior? I possess Beagle Bone Black, but it doesn't have thermal > support (perhaps because its lack of accuracy). > Well, it may happen any system a driver with of-thermal + cpufreq-dt. One board that is easily available is OMAP4460 panda board (tried myself, the problem is there). > With my Exynos setup I didn't experience any problems with this patch. >=20 > >=20 > > The thing is that the bind may happen before cpufreq-dt code loads the > > cpufreq driver, and when cpu_cooling is checking what is the max freq, > > by using cpufreq table, it won't be able to do it, as there is no > > table. >=20 > As I look into the cpufreq-dt.c driver - in the cpufreq_init() > function, the call to of_cpufreq_cooling_register() is performed just > before cpufreq_table_validate_and_show(). > It looks like a mistake in the cpufreq-dt.c code. >=20 Well, I believe for our case, better would be if the cpu_cooling could be done after cpufreq driver registration call. > >=20 > > While, without the patch, it will use wrong in the binding, but after > > it gets bound, and cpufreq loads, the max will be used correctly. >=20 > Correct. Such _wrong_ behavior was the original motivation to prepare > this patch. >=20 > >=20 > > And in this case, the system still works besides this bug.=20 >=20 > Unfortunately there is also a "window" in which the driver is not > properly configured and can cause system crash, although it is unlikely. >=20 Agreed. >=20 > > The > > reasoning is because the max state comes from DT (2) and lower and > > upper wont be equal to THERMAL_NO_LIMIT. Then, the following check > > will use the parameter, instead of max_state: > >=20 > > cdev->ops->get_max_state(cdev, &max_state); > >=20 > > /* lower default 0, upper default max_state */ > > lower =3D lower =3D=3D THERMAL_NO_LIMIT ? 0 : lower; > > upper =3D upper =3D=3D THERMAL_NO_LIMIT ? > > max_state : upper; > >=20 > > In summary, introducing this patch, although it fix a problem, will > > introduce regressions, in of-thermal based drivers. >=20 > To be more precise - it will affect systems, which use of-thermal.c and > cpufreq-dt.c in the same time, due to wrong ordering in the latter file. >=20 Exactly. > Could you give me a hint about the exact affected system? I've grep'ed > for CPUFREQ_DT in the ./arch/arm/configs with no success. >=20 Yeah, the grepping is correct. But well, just because it is not in defconfigs does not mean it won't be used.=20 > >=20 > > I believe, to have this fix, you need to provide a way to have probing > > deferring also in cpu_cooling. That needs also the change in the > > cpufreq driver, as I mentioned in the other thread. >=20 > I will think about possible solution and refer to previous discussion.=20 >=20 Good. For your patch, it is still sane to have it. But needs to be taken after fixing the ordering between cpufreq-dt and cpu_cooling. > >=20 > > Cheers, > >=20 > > > --- > > > drivers/thermal/thermal_core.c | 6 ++++-- > > > 1 file changed, 4 insertions(+), 2 deletions(-) > > >=20 > > > diff --git a/drivers/thermal/thermal_core.c > > > b/drivers/thermal/thermal_core.c index 43b9070..8567929 100644 > > > --- a/drivers/thermal/thermal_core.c > > > +++ b/drivers/thermal/thermal_core.c > > > @@ -928,7 +928,7 @@ int thermal_zone_bind_cooling_device(struct > > > thermal_zone_device *tz, struct thermal_zone_device *pos1; > > > struct thermal_cooling_device *pos2; > > > unsigned long max_state; > > > - int result; > > > + int result, ret; > > > =20 > > > if (trip >=3D tz->trips || (trip < 0 && trip !=3D > > > THERMAL_TRIPS_NONE)) return -EINVAL; > > > @@ -945,7 +945,9 @@ int thermal_zone_bind_cooling_device(struct > > > thermal_zone_device *tz, if (tz !=3D pos1 || cdev !=3D pos2) > > > return -EINVAL; > > > =20 > > > - cdev->ops->get_max_state(cdev, &max_state); > > > + ret =3D cdev->ops->get_max_state(cdev, &max_state); > > > + if (ret) > > > + return ret; > > > =20 > > > /* lower default 0, upper default max_state */ > > > lower =3D lower =3D=3D THERMAL_NO_LIMIT ? 0 : lower; > > > --=20 > > > 2.0.0.rc2 > > >=20 >=20 >=20 > --=20 > Best regards, >=20 > Lukasz Majewski >=20 > Samsung R&D Institute Poland (SRPOL) | Linux Platform Group --ZGiS0Q5IWpPtfppv Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBAgAGBQJUc3KmAAoJEMLUO4d9pOJW6+MH/2OtzuPuyRglPkTJIhtHdZRt 9xEAK/5Rf5HtMFqAFCD7SdKnO0Qt6lkFlXgq0mpCyT6p0FWrUwEm1Axsus5MIKv0 iCMhpAflxYanY06x2uwVbLXlzc+JP9ngJXJjlNlt8PCPn4+jr951Xul2aMf5ixDO Jwtbx6OqCIg3pP1FEh3ln7U7gXMv6+pRC5Nizjh6mn0/LM9T5EW8lnF3nnEh3Qvb OUEgZA/MaK3nxCGRCQLBfU9FijCSdrKjM8Du5KYsJ1pIxx1MipT0uEj6vDT5Flal ImpBwvXp+ivaoOnVySyThYgVnGlArZ1u/Hw94agD2OELG/v9JTQTi0VgwnSf+r0= =pWWw -----END PGP SIGNATURE----- --ZGiS0Q5IWpPtfppv-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/