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

Daniel Kurtz
2015-08-28T02:18:43Z

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.

>
> 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
>