linux-kernel - Re: [PATCH] ACPI: x86: Adjust Microsoft LPS0

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Date:   Thu, 1 Jun 2023 20:46:24 -0500
From:   "Limonciello, Mario" <mario.limonciello@....com>
To:     david.e.box@...ux.intel.com, rafael@...nel.org
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH] ACPI: x86: Adjust Microsoft LPS0 _DSM handling sequence


On 6/1/2023 8:31 PM, David E. Box wrote:
> On Thu, 2023-06-01 at 18:39 -0500, Mario Limonciello wrote:
>> In Windows the Microsoft _DSM doesn't call functions 3->5->7 for suspend
>> and 8->6->4 for resume like Linux currently does.
>>
>> Rather it calls 3->7->5 for suspend and 6->8->4 for resume.
>> Align this calling order for Linux as well.
>>
>> Link:
>> https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/modern-standby-states
> I didn't catch the ordering in the link.

Yeah it's tough to interpret from the link, because the picture at the 
bottom
is missing annotations.

Basically if you look at the picture the blue part is the screen on/off.

The green part is "modern standby" and then the little "humps" are LPS0 
enter/exit.

> Was there any issue that prompted this
> change?


We were debugging an unrelated problem and noticed the difference 
comparing the

BIOS debugging log from Windows and Linux.

If an OEM depends on this call order in that code used in LPS0 phase 
requires
changes from MS phase I could hypothesize this fixes it.


> David

BTW - is there interest in supporting the Microsoft _DSM GUID for Intel 
side too?

It's an incongruity today that we run both AMD GUID and Microsoft GUID 
for AMD systems
but only run Intel GUID for Intel systems.

>
>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>> ---
>>   drivers/acpi/x86/s2idle.c | 14 +++++++-------
>>   1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
>> index e499c60c4579..7214197c15a0 100644
>> --- a/drivers/acpi/x86/s2idle.c
>> +++ b/drivers/acpi/x86/s2idle.c
>> @@ -485,11 +485,11 @@ int acpi_s2idle_prepare_late(void)
>>                                          ACPI_LPS0_ENTRY,
>>                                          lps0_dsm_func_mask, lps0_dsm_guid);
>>          if (lps0_dsm_func_mask_microsoft > 0) {
>> -               acpi_sleep_run_lps0_dsm(ACPI_LPS0_ENTRY,
>> -                               lps0_dsm_func_mask_microsoft,
>> lps0_dsm_guid_microsoft);
>>                  /* modern standby entry */
>>                  acpi_sleep_run_lps0_dsm(ACPI_LPS0_MS_ENTRY,
>>                                  lps0_dsm_func_mask_microsoft,
>> lps0_dsm_guid_microsoft);
>> +               acpi_sleep_run_lps0_dsm(ACPI_LPS0_ENTRY,
>> +                               lps0_dsm_func_mask_microsoft,
>> lps0_dsm_guid_microsoft);
>>          }
>>   
>>          list_for_each_entry(handler, &lps0_s2idle_devops_head, list_node) {
>> @@ -524,11 +524,6 @@ void acpi_s2idle_restore_early(void)
>>                  if (handler->restore)
>>                          handler->restore();
>>   
>> -       /* Modern standby exit */
>> -       if (lps0_dsm_func_mask_microsoft > 0)
>> -               acpi_sleep_run_lps0_dsm(ACPI_LPS0_MS_EXIT,
>> -                               lps0_dsm_func_mask_microsoft,
>> lps0_dsm_guid_microsoft);
>> -
>>          /* LPS0 exit */
>>          if (lps0_dsm_func_mask > 0)
>>                  acpi_sleep_run_lps0_dsm(acpi_s2idle_vendor_amd() ?
>> @@ -539,6 +534,11 @@ void acpi_s2idle_restore_early(void)
>>                  acpi_sleep_run_lps0_dsm(ACPI_LPS0_EXIT,
>>                                  lps0_dsm_func_mask_microsoft,
>> lps0_dsm_guid_microsoft);
>>   
>> +       /* Modern standby exit */
>> +       if (lps0_dsm_func_mask_microsoft > 0)
>> +               acpi_sleep_run_lps0_dsm(ACPI_LPS0_MS_EXIT,
>> +                               lps0_dsm_func_mask_microsoft,
>> lps0_dsm_guid_microsoft);
>> +
>>          /* Screen on */
>>          if (lps0_dsm_func_mask_microsoft > 0)
>>                  acpi_sleep_run_lps0_dsm(ACPI_LPS0_SCREEN_ON,