Messages in this thread | | | Date | Sat, 21 Mar 2020 09:43:21 +0000 | From | Willy Wolff <> | Subject | Re: weird cooling_device/cur_state sysfs behaviour |
| |
Indeed, many thanks for you help.
On Fri, Mar 20, 2020 at 09:17:47pm +0100, Daniel Lezcano wrote: > Adding Rafael, > > On 20/03/2020 18:43, Daniel Lezcano wrote: > > On 20/03/2020 16:10, Willy Wolff wrote: > >> Hi all, > >> Hope you're doing well with the situation. > >> > >> I fill that my board get a cold too... > >> > >> When I write to a sysfs node, I have a weird behaviour about the function that is called behind. > >> This bug appears on an arm32 odroid-xu3, and only after v5.4, v5.3.18 behave correctly. > >> > >> > >> Here my modification to see what's going on: > >> > >> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c > >> index aa99edb4dff7..a437ae3f4b9f 100644 > >> --- a/drivers/thermal/thermal_sysfs.c > >> +++ b/drivers/thermal/thermal_sysfs.c > >> @@ -706,11 +706,22 @@ cur_state_store(struct device *dev, struct device_attribute *attr, > > > > [ ... ] > > > >> return result ? result : count; > >> } > >> > >> + > > > > [ ... ] > > > >> > >> As you can see, the function is recalled with one character less, until the "buffer is empty". > >> I don't understand why. Can anybody help me for this thing? > >> Many thanks in advance. > > > > [ ... ] > > > > Very likely the problem is coming from: > > > > result = cdev->ops->set_cur_state(cdev, state); > > > > which returns '1' as showed by the traces: > > > > drivers/thermal/thermal_sysfs.c:735:cur_state_store result = 1, count = 3 > > > > And because of the return condition above: > > > > return result ? result : count; > > > > the function is returning result, so '1', which is interpreted by the > > sysfs as "I wrote one character', so it recalls the function with the > > two remaining characters, etc ... > > > > The problem is from the governor AFAICT, which governor is it? > > I went through the code and I believe the problem is coming from: > > cpufreq_set_cur_state > -> freq_qos_update_request > -> freq_qos_apply > -> pm_qos_update_target => > > " * This function returns 1 if the aggregated constraint value has changed," > > freq_qos_apply() does: > > ret = pm_qos_update_target() > ... > return ret; > > > At the first glance, it is related to commit 77751a466ebd1 (Nov 2019). > > > > > -- > <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs > > Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | > <http://twitter.com/#!/linaroorg> Twitter | > <http://www.linaro.org/linaro-blog/> Blog >
| |