Hello Lukasz, On Mon, Nov 24, 2014 at 11:38:54AM +0100, Lukasz Majewski wrote: > Hi Eduardo, > > > > > Lukasz, > > > > 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. > > > > > > Signed-off-by: Lukasz Majewski <l.majewski@xxxxxxxxxxx> > > > --- > > > 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. > > > > Have you tried this patch with of-thermal based systems? > > Yes. I did try it with Exynos (after the rework). And there weren't > any regressions. > > To be precise - do you refer to of_cpufreq_cooling_register() [1] or > cpufreq_cooling_register() [2]? > [1] > For the latter [2] - drivers like imx_thermal.c are fully prepared for > -EDEFER_PROBE. > > For the former [1] - only cpufreq-dt.c uses it (and Exynos SoC after > the rework). > > > > > 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. > > I assume, that you mean case [1]? > yup > > > > 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. > > 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. > > > > > 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. > > 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. > Well, I believe for our case, better would be if the cpu_cooling could be done after cpufreq driver registration call. > > > > 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. > > Correct. Such _wrong_ behavior was the original motivation to prepare > this patch. > > > > > And in this case, the system still works besides this bug. > > Unfortunately there is also a "window" in which the driver is not > properly configured and can cause system crash, although it is unlikely. > Agreed. > > > 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: > > > > cdev->ops->get_max_state(cdev, &max_state); > > > > /* lower default 0, upper default max_state */ > > lower = lower == THERMAL_NO_LIMIT ? 0 : lower; > > upper = upper == THERMAL_NO_LIMIT ? > > max_state : upper; > > > > In summary, introducing this patch, although it fix a problem, will > > introduce regressions, in of-thermal based drivers. > > 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. > 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. > Yeah, the grepping is correct. But well, just because it is not in defconfigs does not mean it won't be used. > > > > 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. > > I will think about possible solution and refer to previous discussion. > 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. > > > > Cheers, > > > > > --- > > > drivers/thermal/thermal_core.c | 6 ++++-- > > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > > > 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; > > > > > > if (trip >= tz->trips || (trip < 0 && trip != > > > THERMAL_TRIPS_NONE)) return -EINVAL; > > > @@ -945,7 +945,9 @@ int thermal_zone_bind_cooling_device(struct > > > thermal_zone_device *tz, if (tz != pos1 || cdev != pos2) > > > return -EINVAL; > > > > > > - cdev->ops->get_max_state(cdev, &max_state); > > > + ret = cdev->ops->get_max_state(cdev, &max_state); > > > + if (ret) > > > + return ret; > > > > > > /* lower default 0, upper default max_state */ > > > lower = lower == THERMAL_NO_LIMIT ? 0 : lower; > > > -- > > > 2.0.0.rc2 > > > > > > -- > Best regards, > > Lukasz Majewski > > Samsung R&D Institute Poland (SRPOL) | Linux Platform Group
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