linux-kernel - Re: [PATCH v1 5/9] ACPI: processor: idle: Add the verification of processor FFH LPI state

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Message-ID: <CAJZ5v0g0PgicTEAb3gAeF2D3ZqONNt+6odt2SfGE7XtY3zoPyg@mail.gmail.com>
Date: Thu, 23 Oct 2025 12:35:11 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "lihuisong (C)" <lihuisong@...wei.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, lenb@...nel.org, linux-acpi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Sudeep.Holla@....com, linuxarm@...wei.com, 
	jonathan.cameron@...wei.com, zhanjie9@...ilicon.com, zhenglifeng1@...wei.com, 
	yubowen8@...wei.com
Subject: Re: [PATCH v1 5/9] ACPI: processor: idle: Add the verification of
 processor FFH LPI state

On Thu, Oct 23, 2025 at 12:17 PM lihuisong (C) <lihuisong@...wei.com> wrote:
>
>
> 在 2025/10/22 3:42, Rafael J. Wysocki 写道:
> > On Mon, Sep 29, 2025 at 11:38 AM Huisong Li <lihuisong@...wei.com> wrote:
> >> Both ARM64 and RISCV architecture would validate Entry Method of LPI
> >> state and SBI HSM or PSCI cpu suspend. Driver should return failure
> >> if FFH of LPI state are not ok.
> > First of all, I cannot parse this changelog, so I don't know the
> > motivation for the change.
> Sorry for your confusion.
> > Second, if _LPI is ever used on x86, the
> > acpi_processor_ffh_lpi_probe() in acpi_processor_get_power_info() will
> > get in the way.
> AFAICS, it's also ok if X86 platform use LPI.

No, because it returns an error by default as it stands today.

> >
> > Why does the evaluation in acpi_processor_setup_cpuidle_dev() not work?
> The acpi_processor_ffh_lpi_probe does verify the validity of LPI for ARM
> and RISCV.
> But the caller of the acpi_processor_setup_cpuidle_dev()don't verify the
> return value.
> In addition, from the name of acpi_processor_setup_cpuidle_dev(), its
> main purpose is to setup cpudile device rather than to verify LPI.

That's fair enough.

Also, the list of idle states belongs to the cpuidle driver, not to a
cpuidle device.

> So I move it to a more prominent position and redefine the
> acpi_processor_setup_cpuidle_dev to void in patch 9/9.
> >
> >> Fixes: a36a7fecfe60 ("ACPI / processor_idle: Add support for Low Power Idle(LPI) states")
> >> Signed-off-by: Huisong Li <lihuisong@...wei.com>
> >> ---
> >>   drivers/acpi/processor_idle.c | 10 ++++++++--
> >>   1 file changed, 8 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> >> index 5684925338b3..b0d6b51ee363 100644
> >> --- a/drivers/acpi/processor_idle.c
> >> +++ b/drivers/acpi/processor_idle.c
> >> @@ -1264,7 +1264,7 @@ static int acpi_processor_setup_cpuidle_dev(struct acpi_processor *pr,
> >>
> >>          dev->cpu = pr->id;
> >>          if (pr->flags.has_lpi)
> >> -               return acpi_processor_ffh_lpi_probe(pr->id);
> >> +               return 0;
> >>
> >>          return acpi_processor_setup_cpuidle_cx(pr, dev);
> >>   }
> >> @@ -1275,7 +1275,13 @@ static int acpi_processor_get_power_info(struct acpi_processor *pr)
> >>
> >>          ret = acpi_processor_get_lpi_info(pr);
> >>          if (ret)

So I think it would be better to check it here, that is

if (!ret) {
       ret = acpi_processor_ffh_lpi_probe(pr->id));
       if (!ret)
               return 0;

       pr_info("CPU%d: FFH LPI state is invalid\n", pr->id);
       pr->flags.has_lpi = 0;
}

return acpi_processor_get_cstate_info(pr);

And the default acpi_processor_ffh_lpi_probe() needs to be changed to return 0.

> >> -               ret = acpi_processor_get_cstate_info(pr);
> >> +               return acpi_processor_get_cstate_info(pr);
> >> +
> >> +       if (pr->flags.has_lpi) {
> >> +               ret = acpi_processor_ffh_lpi_probe(pr->id);
> >> +               if (ret)
> >> +                       pr_err("Processor FFH LPI state is invalid.\n");
> >> +       }
> >>
> >>          return ret;
> >>   }
> >> --