linux-kernel - Re: [RFC PATCH v4 8/8] acpi_idle: Disallow play

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Message-ID: <3f764538-eaa5-4446-995c-d6b32c891b66@linux.intel.com>
Date: Tue, 26 Nov 2024 13:05:42 +0100
From: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
To: "Gautham R. Shenoy" <gautham.shenoy@....com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
 rafael.j.wysocki@...el.com, len.brown@...el.com,
 artem.bityutskiy@...ux.intel.com, dave.hansen@...ux.intel.com,
 peterz@...radead.org, tglx@...utronix.de
Subject: Re: [RFC PATCH v4 8/8] acpi_idle: Disallow play_dead with FFH cstate
 on AMD platforms

On 11/25/24 4:15 PM, Gautham R. Shenoy wrote:
> On Mon, Nov 25, 2024 at 02:20:28PM +0100, Patryk Wlazlyn wrote:
>> Signed-off-by: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
>> Suggested-by: Gautham R. Shenoy <gautham.shenoy@....com>
>
> You can drop this patch. It is very rare to find a platform that
> supports FFH based C1 and doesn't have a IOPORT based C2.
>
> --
> Thanks and Regards
> gautham.
>
>
>> ---
>>  drivers/acpi/processor_idle.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
>> index 586cc7d1d8aa..4b4ac8d55b55 100644
>> --- a/drivers/acpi/processor_idle.c
>> +++ b/drivers/acpi/processor_idle.c
>> @@ -803,7 +803,11 @@ static int acpi_processor_setup_cstates(struct acpi_processor *pr)
>>  
>>          state->flags = 0;
>>  
>> -        state->enter_dead = acpi_idle_play_dead;
>> +        /* AMD doesn't want to use mwait for play dead. */
>> +        bool amd_or_hygon = boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
>> +                    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON;
>> +        if (!(cx->entry_method == ACPI_CSTATE_FFH && amd_or_hygon))
>> +            state->enter_dead = acpi_idle_play_dead;
>>  
>>          if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2)
>>              drv->safe_state_index = count;
>> --
>> 2.47.0
>>

ACK, thanks!