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SubjectRe: [PATCH v2 1/4] ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops
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On 8/29/2022 09:20, Rafael J. Wysocki wrote:
> On Mon, Aug 29, 2022 at 3:29 PM Mario Limonciello
> <mario.limonciello@amd.com> wrote:
>>
>> On some platforms it is found that Linux more aggressively enters s2idle
>> than Windows enters Modern Standby and this uncovers some synchronization
>> issues for the platform. To aid in debugging this class of problems in
>> the future, add support for an extra optional callback intended for
>> drivers to emit extra debugging.
>
> I'm not liking this.
>
> If you want debug, why not simply add it where it is needed?

Actually this is exactly where it's needed. The synchronization issue
is with what non-x86 is doing while x86 transitions into ACPI C3.

>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v1->v2:
>> * Add a prototype for `acpi_s2idle_enter`
>>
>> drivers/acpi/sleep.h | 1 +
>> drivers/acpi/x86/s2idle.c | 14 ++++++++++++++
>> include/linux/acpi.h | 1 +
>> include/linux/suspend.h | 1 +
>> kernel/power/suspend.c | 3 +++
>> 5 files changed, 20 insertions(+)
>>
>> diff --git a/drivers/acpi/sleep.h b/drivers/acpi/sleep.h
>> index 7fe41ee489d6..7856930a7da9 100644
>> --- a/drivers/acpi/sleep.h
>> +++ b/drivers/acpi/sleep.h
>> @@ -18,6 +18,7 @@ static inline acpi_status acpi_set_waking_vector(u32 wakeup_address)
>> extern int acpi_s2idle_begin(void);
>> extern int acpi_s2idle_prepare(void);
>> extern int acpi_s2idle_prepare_late(void);
>> +extern void acpi_s2idle_enter(void);
>
> And this name is confusing, because it suggests that the role of the
> callback is to make the platform enter s2idle which isn't the case.

Can you propose another name?

>
>> extern bool acpi_s2idle_wake(void);
>> extern void acpi_s2idle_restore_early(void);
>> extern void acpi_s2idle_restore(void);
>> diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
>> index f9ac12b778e6..c984093a3657 100644
>> --- a/drivers/acpi/x86/s2idle.c
>> +++ b/drivers/acpi/x86/s2idle.c
>> @@ -486,6 +486,19 @@ int acpi_s2idle_prepare_late(void)
>> return 0;
>> }
>>
>> +void acpi_s2idle_enter(void)
>> +{
>> + struct acpi_s2idle_dev_ops *handler;
>> +
>> + if (!lps0_device_handle || sleep_no_lps0)
>> + return;
>> +
>> + list_for_each_entry(handler, &lps0_s2idle_devops_head, list_node) {
>> + if (handler->enter)
>> + handler->enter();
>> + }
>> +}
>> +
>> void acpi_s2idle_restore_early(void)
>> {
>> struct acpi_s2idle_dev_ops *handler;
>> @@ -527,6 +540,7 @@ static const struct platform_s2idle_ops acpi_s2idle_ops_lps0 = {
>> .begin = acpi_s2idle_begin,
>> .prepare = acpi_s2idle_prepare,
>> .prepare_late = acpi_s2idle_prepare_late,
>> + .enter = acpi_s2idle_enter,
>> .wake = acpi_s2idle_wake,
>> .restore_early = acpi_s2idle_restore_early,
>> .restore = acpi_s2idle_restore,
>> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> index 6f64b2f3dc54..9df14b5a875c 100644
>> --- a/include/linux/acpi.h
>> +++ b/include/linux/acpi.h
>> @@ -1076,6 +1076,7 @@ struct acpi_s2idle_dev_ops {
>> struct list_head list_node;
>> void (*prepare)(void);
>> void (*restore)(void);
>> + void (*enter)(void);
>> };
>> int acpi_register_lps0_dev(struct acpi_s2idle_dev_ops *arg);
>> void acpi_unregister_lps0_dev(struct acpi_s2idle_dev_ops *arg);
>> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
>> index 70f2921e2e70..5a3fdca0a628 100644
>> --- a/include/linux/suspend.h
>> +++ b/include/linux/suspend.h
>> @@ -191,6 +191,7 @@ struct platform_s2idle_ops {
>> int (*begin)(void);
>> int (*prepare)(void);
>> int (*prepare_late)(void);
>> + void (*enter)(void);
>> bool (*wake)(void);
>> void (*restore_early)(void);
>> void (*restore)(void);
>> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
>> index 827075944d28..0c08032d6b50 100644
>> --- a/kernel/power/suspend.c
>> +++ b/kernel/power/suspend.c
>> @@ -136,6 +136,9 @@ static void s2idle_loop(void)
>> break;
>> }
>>
>> + if (s2idle_ops && s2idle_ops->enter)
>> + s2idle_ops->enter();
>> +
>> s2idle_enter();
>> }
>>
>> --
>> 2.34.1
>>

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