Hi Andrzej,

On 17/04/2020 18:20, Andrzej Pietrasiewicz wrote:

Thermal zone devices' mode is stored in individual drivers. This patch
changes it so that mode is stored in struct thermal_zone_device instead.

As a result all driver-specific variables storing the mode are not needed
and are removed. Consequently, the get_mode() implementations have nothing
to operate on and need to be removed, too.

Some thermal framework specific functions are introduced:

thermal_zone_device_get_mode()
thermal_zone_device_set_mode()
thermal_zone_device_enable()
thermal_zone_device_disable()

thermal_zone_device_get_mode() and its "set" counterpart take tzd's lock
and the "set" calls driver's set_mode() if provided, so the latter must
not take this lock again. At the end of the "set"
thermal_zone_device_update() is called so drivers don't need to repeat this
invocation in their specific set_mode() implementations.

The scope of the above 4 functions is purposedly limited to the thermal
framework and drivers are not supposed to call them. This encapsulation
does not fully work at the moment for some drivers, though:

- platform/x86/acerhdf.c
- drivers/thermal/imx_thermal.c
- drivers/thermal/intel/intel_quark_dts_thermal.c
- drivers/thermal/of-thermal.c

and they manipulate struct thermal_zone_device's members directly.

struct thermal_zone_params gains a new member called initial_mode, which
is used to set tzd's mode at registration time.

The sysfs "mode" attribute is always exposed from now on, because all
thermal zone devices now have their get_mode() implemented at the generic
level and it is always available. Exposing "mode" doesn't hurt the drivers
which don't provide their own set_mode(), because writing to "mode" will
result in -EPERM, as expected.

The result is great, that is a nice cleanup of the thermal framework.

After review it appears there are still problems IMO, especially with
the suspend / resume path. The patch is big, it is a bit complex to
comment. I suggest to re-org the changes as following:

 - patch 1 : Add the four functions:

 * thermal_zone_device_set_mode()
 * thermal_zone_device_enable()
 * thermal_zone_device_disable()
 * thermal_zone_device_is_enabled()

*but* do not export thermal_zone_device_set_mode(), it must stay private
to the thermal framework ATM.

 - patch 2 : Add the mode THERMAL_DEVICE_SUSPENDED

In the thermal_pm_notify() in the:

 - PM_SUSPEND_PREPARE case, set the mode to THERMAL_DEVICE_SUSPENDED if
the mode is THERMAL_DEVICE_ENABLED

 - PM_POST_SUSPEND case, set the mode to THERMAL_DEVICE_ENABLED, if the
mode is THERMAL_DEVICE_SUSPENDED

 - patch 3 : Change the monitor function

Change monitor_thermal_zone() function to set the polling to zero if the
mode is THERMAL_DEVICE_DISABLED

 - patch 4 : Do the changes to remove get_mode() ops

Make sure there is no access to tz->mode from the drivers anymore but
use of the functions of patch 1. IMO, this is the tricky part because a
part of the drivers are not calling the update after setting the mode
while the function thermal_zone_device_enable()/disable() call update
via the thermal_zone_device_set_mode(), so we must be sure to not break
anything.

 - patch 5 : Do the changes to remove set_mode() ops users

As the patch 3 sets the polling to zero, the routine in the driver
setting the polling to zero is no longer needed (eg. in the mellanox
driver). I expect int300 to be the last user of this ops, hopefully we
can find a way to get rid of the specific call done inside and then
remove the ops.

The initial_mode approach looks hackish, I suggest to make the default
the thermal zone disabled after creating and then explicitly enable it.
Note that is what do a lot of drivers already.

Hopefully, these changes are git-bisect safe.

Does it make sense ?












-- 
<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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel