Re: [PATCH v4 4/5] thermal: power_allocator: don't require tzp to be present for the thermal zone

Daniel Kurtz
2015-08-31T13:15:11Z

Hi Javi,

On Sat, Aug 29, 2015 at 12:28 AM, Javi Merino <javi.merino@arm.com> wrote:
> On Fri, Aug 28, 2015 at 03:18:20AM +0100, Daniel Kurtz wrote:
>> On Wed, Aug 26, 2015 at 9:26 PM, Javi Merino <javi.merino@arm.com> wrote:
>> > Thermal zones created using thermal_zone_device_create() may not have
>> > tzp. As the governor gets its parameters from there, allocate it while
>> > the governor is bound to the thermal zone so that it can operate in it.
>> > In this case, tzp is freed when the thermal zone switches to another
>> > governor.
>> >
>> > Cc: Zhang Rui <rui.zhang@intel.com>
>> > Cc: Eduardo Valentin <edubezval@gmail.com>
>> > Signed-off-by: Javi Merino <javi.merino@arm.com>
>> > ---
>> >
>> > While this would be easier to do by just ignoring the thermal zone if
>> > there was no tzp, I think the approach in this patch provides a better
>> > behavior.
>>
>> Why?
>> Just ignoring the thermal zone seems reasonable and simpler.
>
> From the developer point of view, I agree that it's simpler. What I
> want to avoid is the system integrator getting different behaviors
> based on the presence of tzp when the thermal zone was created. If
> the integrator was to configure this from userspace, they would only
> be able to do so if the thermal zone was created with tzp. I don't
> like this distinction, I prefer the consistency from the user point of
> view that this patch gives.

Ok, thanks for the answer.

Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>

Thanks!
-Dan

>
> Cheers,
> Javi
>
>> > drivers/thermal/power_allocator.c | 32 +++++++++++++++++++++++++++-----
>> > 1 file changed, 27 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/drivers/thermal/power_allocator.c b/drivers/thermal/power_allocator.c
>> > index 2dfb8ade4d1b..85ce0aac9a41 100644
>> > --- a/drivers/thermal/power_allocator.c
>> > +++ b/drivers/thermal/power_allocator.c
>> > @@ -58,6 +58,8 @@ static inline s64 div_frac(s64 x, s64 y)
>> >
>> > /**
>> > * struct power_allocator_params - parameters for the power allocator governor
>> > + * @allocated_tzp: whether we have allocated tzp for this thermal zone and
>> > + * it needs to be freed on unbind
>> > * @err_integral: accumulated error in the PID controller.
>> > * @prev_err: error in the previous iteration of the PID controller.
>> > * Used to calculate the derivative term.
>> > @@ -70,6 +72,7 @@ static inline s64 div_frac(s64 x, s64 y)
>> > * controlling for.
>> > */
>> > struct power_allocator_params {
>> > + bool allocated_tzp;
>> > s64 err_integral;
>> > s32 prev_err;
>> > int trip_switch_on;
>> > @@ -530,8 +533,7 @@ static void allow_maximum_power(struct thermal_zone_device *tz)
>> > * Initialize the PID controller parameters and bind it to the thermal
>> > * zone.
>> > *
>> > - * Return: 0 on success, -EINVAL if the thermal zone doesn't have tzp or -ENOMEM
>> > - * if we ran out of memory.
>> > + * Return: 0 on success, or -ENOMEM if we ran out of memory.
>> > */
>> > static int power_allocator_bind(struct thermal_zone_device *tz)
>> > {
>> > @@ -539,13 +541,20 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
>> > struct power_allocator_params *params;
>> > unsigned long control_temp;
>> >
>> > - if (!tz->tzp)
>> > - return -EINVAL;
>> > -
>> > params = kzalloc(sizeof(*params), GFP_KERNEL);
>> > if (!params)
>> > return -ENOMEM;
>> >
>> > + if (!tz->tzp) {
>> > + tz->tzp = kzalloc(sizeof(*tz->tzp), GFP_KERNEL);
>>
>> Why bother to allocate this dummy struct?
>> Can't we just leave tz->tzp as NULL, and do a NULL check where needed?
>>
>> > + if (!tz->tzp) {
>> > + ret = -ENOMEM;
>> > + goto free_params;
>> > + }
>> > +
>> > + params->allocated_tzp = true;
>> > + }
>> > +
>> > if (!tz->tzp->sustainable_power)
>> > dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
>> >
>> > @@ -562,11 +571,24 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
>> > tz->governor_data = params;
>> >
>> > return 0;
>> > +
>> > +free_params:
>> > + kfree(params);
>> > +
>> > + return ret;
>> > }
>> >
>> > static void power_allocator_unbind(struct thermal_zone_device *tz)
>> > {
>> > + struct power_allocator_params *params = tz->governor_data;
>> > +
>> > dev_dbg(&tz->device, "Unbinding from thermal zone %d\n", tz->id);
>> > +
>> > + if (params->allocated_tzp) {
>> > + kfree(tz->tzp);
>> > + tz->tzp = NULL;
>> > + }
>> > +
>> > kfree(tz->governor_data);
>> > tz->governor_data = NULL;
>> > }
>> > --
>> > 1.9.1
>> >
>>