linux-kernel - Re: [PATCH] thermal: gov_power_allocator: Update total

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Message-ID: <32fe0e71-e8d9-4404-8b48-a8b8e9ec71e7@arm.com>
Date: Fri, 21 Feb 2025 10:43:00 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Yu-Che Cheng <giver@...omium.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>,
 Zhang Rui <rui.zhang@...el.com>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, Chen-Yu Tsai <wenst@...omium.org>
Subject: Re: [PATCH] thermal: gov_power_allocator: Update total_weight on bind
 and cdev updates



On 2/20/25 19:40, Rafael J. Wysocki wrote:
> On Wed, Feb 19, 2025 at 8:07 AM Yu-Che Cheng <giver@...omium.org> wrote:
>>
>> params->total_weight is not initialized during bind and not updated when
>> the bound cdev changes. The cooling device weight will not be used due
>> to the uninitialized total_weight, until we trigger an update via sysfs.
>>
>> The bound cdev update will be triggered during thermal zone registration,
>> where each cooling device will be bound to the thermal zone one by one.
>>
>> The power_allocator_bind can be called without additional cdev update
>> when manually changing the policy of a thermal zone via sysfs.

Thanks Yu-Che for catching this.

>>
>> Update total_weight when bind and cdev updates to ensure total_weight is
>> correct.
>>
>> Fixes: a3cd6db4cc2e ("thermal: gov_power_allocator: Support new update callback of weights")
>> Signed-off-by: Yu-Che Cheng <giver@...omium.org>
>> ---
>>   drivers/thermal/gov_power_allocator.c | 9 +++++----
>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
>> index 3b644de3292e..600cb0e367c3 100644
>> --- a/drivers/thermal/gov_power_allocator.c
>> +++ b/drivers/thermal/gov_power_allocator.c
>> @@ -656,11 +656,10 @@ static void power_allocator_update_tz(struct thermal_zone_device *tz,
>>                          if (power_actor_is_valid(instance))
>>                                  num_actors++;
>>
>> -               if (num_actors == params->num_actors)
>> -                       return;
>> +               if (num_actors != params->num_actors)
>> +                       allocate_actors_buffer(params, num_actors);
>>
>> -               allocate_actors_buffer(params, num_actors);
>> -               break;
>> +               fallthrough;
> 
> This is basically fine, but I would add a new function, say
> power_allocator_update_weight(), for updating the weight.
> 
>>          case THERMAL_INSTANCE_WEIGHT_CHANGED:
> 
> And I'd call it from here and from power_allocator_bind() below.
> 
>>                  params->total_weight = 0;
>>                  list_for_each_entry(instance, &td->thermal_instances, trip_node)
>> @@ -731,6 +730,8 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
>>
>>          tz->governor_data = params;
>>
>> +       power_allocator_update_tz(tz, THERMAL_INSTANCE_WEIGHT_CHANGED);
> 
> Because this is kind of confusing (although it will work AFAICS).
> 

Thanks Rafael, I agree with suggestions. It would look cleaner.