Re: [PATCH] cpufreq: Fix initialization with disabled boost

[Robin Murphy]

On 17/06/2025 9:20 am, Christian Loehle wrote:
> On 6/17/25 03:14, zhenglifeng (A) wrote:
> > On 2025/6/17 3:10, Robin Murphy wrote:
> > > On 2025-06-16 6:25 pm, Christian Loehle wrote:
> > > > The boost_enabled early return in policy_set_boost() caused
> > > > the boost disabled at initialization to not actually set the
> > > > initial policy->max, therefore effectively enabling boost while
> > > > it should have been enabled.
> > > >
> > > > Fixes: 27241c8b63bd ("cpufreq: Introduce policy_set_boost()")
> > >
> > > I think it's a bit older than that - I noticed this with 6.15 stable, prior to that refactoring, and from a poke through the history the underlying logic appears to date back to dd016f379ebc ("cpufreq: Introduce a more generic way to set default per-policy boost flag"). Hopefully someone can figure out the appropriate stable backport.
> > >
> > > I can at least confirm that equivalently hacking out the "&& policy->boost_enabled != cpufreq_boost_enabled()" condition previously here does have the desired effect for me of initialising scaling_max_freq correctly at boot, but I'm not sure that's entirely correct on its own...
> > >
> > > Thanks,
> > > Robin.
> > >
> > > > Reported-by: Robin Murphy <robin.murphy@xxxxxxx>
> > > > Signed-off-by: Christian Loehle <christian.loehle@xxxxxxx>
> > > > ---
> > > >    drivers/cpufreq/cpufreq.c | 2 +-
> > > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > > > index d7426e1d8bdd..e85139bd0436 100644
> > > > --- a/drivers/cpufreq/cpufreq.c
> > > > +++ b/drivers/cpufreq/cpufreq.c
> > > > @@ -1630,7 +1630,7 @@ static int cpufreq_online(unsigned int cpu)
> > > >         */
> > > >        if (cpufreq_driver->set_boost && policy->boost_supported &&
> > > >            (new_policy || !cpufreq_boost_enabled())) {
> > > > -        ret = policy_set_boost(policy, cpufreq_boost_enabled());
> > > > +        ret = cpufreq_driver->set_boost(policy, cpufreq_boost_enabled());
> > > >            if (ret) {
> > > >                /* If the set_boost fails, the online operation is not affected */
> > > >                pr_info("%s: CPU%d: Cannot %s BOOST\n", __func__, policy->cpu,
> >
> > I don't quite understand what problem you've met. It semms like you guys
> > propose that set_boost() should be called no matter what
> > policy->boost_enabled is. Having more details would help to clarify things,
> > such as which driver you use and what you expect but not be achieved.
>
> so calling policy_set_boost(policy, enable) is a noop here if
> policy->boost_enabled == cpufreq_boost_enabled():
>
> 	if (policy->boost_enabled == enable)
> 		return 0;
>
> We have policy->boost_enabled == false on boot, thus never actually
> setting policy->max up ever, which leads to the following:

And for clarity, this is with the cpufreq_dt driver (at least in my case).

Thanks,
Robin.

> # cat /sys/devices/system/cpu/cpufreq/policy4/scaling_boost_frequencies
> 2016000
> # cat /sys/devices/system/cpu/cpufreq/policy4/scaling_max_freq
> 2016000
> # cat /sys/devices/system/cpu/cpufreq/boost
> 0
> # echo 1 > /sys/devices/system/cpu/cpufreq/boost
> # echo 0 > /sys/devices/system/cpu/cpufreq/boost
> # cat /sys/devices/system/cpu/cpufreq/policy4/scaling_boost_frequencies
> 1800000
>
> Anyway I'll bisect some more to find the actual first bad commit and
> resend.