Re: [PATCH] cpufreq/cppc: fix perf_to_khz conversion exception

[liwei (JK)]

Hello Pierre,

Thanks for your reminder.

在 2024/5/3 15:42, Pierre Gondois 写道:
> Hello Liwei,
>
> Thanks for the fix. I think there might be a similar issue
> in cppc_khz_to_perf(),
>
> Regards,
> Pierre

cppc_khz_to_perf() also has similar issue, I will modify the patch again.

Liwei

> On 4/30/24 12:12, liwei wrote:
> > When the nominal_freq recorded by the kernel is equal to lowest_freq and
> > the frequency reduction operation is triggered externally, there is a
> > conversion logic error in cppc_perf_to_khz(), causing the kernel to be
> > unable to feedback the true frequency.
> >
> > Fix this by adding the branch processing logic when nominal_freq is equal
> > to lowest_freq.
> >
> > Fixes: ec1c7ad47664 ("cpufreq: CPPC: Fix performance/frequency 
> > conversion")
> > Signed-off-by: liwei <liwei728@xxxxxxxxxx>
> > ---
> >   drivers/acpi/cppc_acpi.c | 10 ++++++++--
> >   1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> > index a40b6f3946ef..92aac6974e0e 100644
> > --- a/drivers/acpi/cppc_acpi.c
> > +++ b/drivers/acpi/cppc_acpi.c
> > @@ -1869,9 +1869,15 @@ unsigned int cppc_perf_to_khz(struct 
> > cppc_perf_caps *caps, unsigned int perf)
> >       u64 mul, div;
> >       if (caps->lowest_freq && caps->nominal_freq) {
> > -        mul = caps->nominal_freq - caps->lowest_freq;
> > +        /* Avoid the special case when nominal_freq is equal to 
> > lowest_freq */
> > +        if (caps->lowest_freq == caps->nominal_freq) {
> > +            mul = caps->nominal_freq;
> > +            div = caps->nominal_perf;
> > +        } else {
> > +            mul = caps->nominal_freq - caps->lowest_freq;
> > +            div = caps->nominal_perf - caps->lowest_perf;
> > +        }
> >           mul *= KHZ_PER_MHZ;
> > -        div = caps->nominal_perf - caps->lowest_perf;
> >           offset = caps->nominal_freq * KHZ_PER_MHZ -
> >                div64_u64(caps->nominal_perf * mul, div);
> >       } else {