linux-kernel - Re: [PATCH] thermal: gov_power_allocator: Fix incorrect calculation in divvy_up

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Message-ID: <CAJZ5v0ikFjYsCfzYX6utX4=sraaBYH==Vdwz7ZPU9gHX=JaGgA@mail.gmail.com>
Date: Fri, 21 Feb 2025 18:15:00 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Lukasz Luba <lukasz.luba@....com>, 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: Fix incorrect calculation
 in divvy_up_power

On Fri, Feb 21, 2025 at 11:35 AM Lukasz Luba <lukasz.luba@....com> wrote:
>
>
>
> On 2/20/25 19:45, Rafael J. Wysocki wrote:
> > On Wed, Feb 19, 2025 at 8:07 AM Yu-Che Cheng <giver@...omium.org> wrote:
> >>
> >> divvy_up_power should use weighted_req_power instead of req_power to
> >> calculate the granted_power. Otherwise, the granted_power may be
> >> unexpected as the denominator total_req_power is weighted sum.
> >
> > Yes, this is what's happening, to my eyes.
> >
> >> This is a mistake during the previous refactor.
> >>
> >> Replace the req_power with weighted_req_power in divvy_up_power
> >> calculation.
> >>
> >> Fixes: 912e97c67cc3 ("thermal: gov_power_allocator: Move memory allocation out of throttle()")
> >> Signed-off-by: Yu-Che Cheng <giver@...omium.org>
> >> ---
> >>   drivers/thermal/gov_power_allocator.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
> >> index 3b644de3292e..3b626db55b2b 100644
> >> --- a/drivers/thermal/gov_power_allocator.c
> >> +++ b/drivers/thermal/gov_power_allocator.c
> >> @@ -370,7 +370,7 @@ static void divvy_up_power(struct power_actor *power, int num_actors,
> >>
> >>          for (i = 0; i < num_actors; i++) {
> >>                  struct power_actor *pa = &power[i];
> >> -               u64 req_range = (u64)pa->req_power * power_range;
> >> +               u64 req_range = (u64)pa->weighted_req_power * power_range;
> >>
> >>                  pa->granted_power = DIV_ROUND_CLOSEST_ULL(req_range,
> >>                                                            total_req_power);
> >>
> >> ---
> >
> > And the fix looks good to me.
> >
> > Lukasz, any concerns?
>
> Good catch! It went through since the test didn't set different weights.
>
> Thanks for the fix!
>
> Reviewed-by: Lukasz Luba <lukasz.luba@....com>

Applied as 6.14-rc material, thanks!