Re: [PATCH] x86/ACPI/State: Optimize C3 entry on AMD CPUs

Sharma, Deepak
2021-09-22T03:50:24Z

Hi Rafael,

On 9/1/2021 5:45 AM, Rafael J. Wysocki wrote:
> On Wed, Sep 1, 2021 at 4:14 AM Deepak Sharma <deesharm@amd.com> wrote:
>>
>> On 8/25/21 11:07 AM, Rafael J. Wysocki wrote:
>>> On Thu, Aug 19, 2021 at 2:43 AM Deepak Sharma <deepak.sharma@amd.com> wrote:
>>>> AMD CPU which support C3 shares cache. Its not necessary to flush the
>>>> caches in software before entering C3. This will cause performance drop
>>>> for the cores which share some caches. ARB_DIS is not used with current
>>>> AMD C state implementation. So set related flags correctly.
>>>>
>>>> Signed-off-by: Deepak Sharma <deepak.sharma@amd.com>
>>> Applied as 5.15 material under the edited subject "x86: ACPI: cstate:
>>> Optimize C3 entry on AMD CPUs", thanks!
>> I might need to send subsequent patch for this. Can you please point me
>> to git and branch where this has been merged.
> git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next

Still I am not able to see this patch merged on linux-next branch.

Thanks,

Deepak

>>>> ---
>>>> arch/x86/kernel/acpi/cstate.c | 15 +++++++++++++++
>>>> 1 file changed, 15 insertions(+)
>>>>
>>>> diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
>>>> index 7de599eba7f0..62a5986d625a 100644
>>>> --- a/arch/x86/kernel/acpi/cstate.c
>>>> +++ b/arch/x86/kernel/acpi/cstate.c
>>>> @@ -79,6 +79,21 @@ void acpi_processor_power_init_bm_check(struct acpi_processor_flags *flags,
>>>> */
>>>> flags->bm_control = 0;
>>>> }
>>>> + if (c->x86_vendor == X86_VENDOR_AMD) {
>>>> + /*
>>>> + * For all AMD CPUs that support C3, caches should not be
>>>> + * flushed by software while entering C3 type state. Set
>>>> + * bm->check to 1 so that kernel doesn't need to execute
>>>> + * cache flush operation.
>>>> + */
>>>> + flags->bm_check = 1;
>>>> + /*
>>>> + * In current AMD C state implementation ARB_DIS is no longer
>>>> + * used. So set bm_control to zero to indicate ARB_DIS is not
>>>> + * required while entering C3 type state.
>>>> + */
>>>> + flags->bm_control = 0;
>>>> + }
>>>> }
>>>> EXPORT_SYMBOL(acpi_processor_power_init_bm_check);
>>>>
>>>> --
>>>> 2.25.1
>>>>