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

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Message-ID: <ab814879-37d6-49dc-8a38-6b94cabf9327@huawei.com>
Date: Fri, 24 Oct 2025 17:40:41 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
CC: <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


在 2025/10/23 18:35, Rafael J. Wysocki 写道:
> 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.
Sorry, I don't understand why pr->flags.has_lpi is true if 
acpi_processor_ffh_lpi_probe() return failure.
In addition, X86 platform doesn't define acpi_processor_ffh_lpi_probe(). 
this function will return EOPNOTSUPP.
>
>>>> -               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;
>>>>    }
>>>> --