[PATCH v2 0/4] Add some extra debugging mechanisms for s0i3

[PATCH v2 0/4] Add some extra debugging mechanisms for s0i3

[Mario Limonciello]

Recently there have been reports of problems where the system consumes
too much power after certain interrupts occur that would notify the
kernel of some event but those events aren't marked for wakeup.

These problems have been root caused to the timing of the kernel moving
the cores into ACPI C3 relative to other events from the previous wakeup
not being settled.  Linux will more aggressively move the cores into C3
for s2idle than Windows does for Modern Standby.

To aide with debugging this class of problems in the future add a new
set of optional debugging infrastructure.

Mario Limonciello (4):
  ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops
  platform/x86/amd: pmc: Add defines for STB events
  platform/x86/amd: pmc: Always write to the STB
  platform/x86/amd: pmc: Add an extra STB message for entering s2idle

 drivers/acpi/sleep.h           |  1 +
 drivers/acpi/x86/s2idle.c      | 14 ++++++++++++++
 drivers/platform/x86/amd/pmc.c | 32 ++++++++++++++++++++------------
 include/linux/acpi.h           |  1 +
 include/linux/suspend.h        |  1 +
 kernel/power/suspend.c         |  3 +++
 6 files changed, 40 insertions(+), 12 deletions(-)

-- 
2.34.1

[PATCH v2 1/4] ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops

[Mario Limonciello]

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.

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);
 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

[PATCH v2 2/4] platform/x86/amd: pmc: Add defines for STB events

[Mario Limonciello]

Currently `amd-pmc` has two events, but just adds one to the first to
distinguish the second.  Add a clear definition what these events mean.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/platform/x86/amd/pmc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/amd/pmc.c b/drivers/platform/x86/amd/pmc.c
index 700eb19e8450..39e6ab88861d 100644
--- a/drivers/platform/x86/amd/pmc.c
+++ b/drivers/platform/x86/amd/pmc.c
@@ -39,7 +39,8 @@
 #define AMD_PMC_STB_INDEX_ADDRESS	0xF8
 #define AMD_PMC_STB_INDEX_DATA		0xFC
 #define AMD_PMC_STB_PMI_0		0x03E30600
-#define AMD_PMC_STB_PREDEF		0xC6000001
+#define AMD_PMC_STB_S2IDLE_PREPARE	0xC6000001
+#define AMD_PMC_STB_S2IDLE_RESTORE	0xC6000002
 
 /* STB S2D(Spill to DRAM) has different message port offset */
 #define STB_SPILL_TO_DRAM		0xBE
@@ -701,7 +702,7 @@ static void amd_pmc_s2idle_prepare(void)
 	}
 
 	if (enable_stb) {
-		rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_PREDEF);
+		rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_S2IDLE_PREPARE);
 		if (rc)
 			dev_err(pdev->dev, "error writing to STB: %d\n", rc);
 	}
@@ -724,9 +725,8 @@ static void amd_pmc_s2idle_restore(void)
 	/* Dump the IdleMask to see the blockers */
 	amd_pmc_idlemask_read(pdev, pdev->dev, NULL);
 
-	/* Write data incremented by 1 to distinguish in stb_read */
 	if (enable_stb) {
-		rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_PREDEF + 1);
+		rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_S2IDLE_RESTORE);
 		if (rc)
 			dev_err(pdev->dev, "error writing to STB: %d\n", rc);
 	}
-- 
2.34.1

[PATCH v2 3/4] platform/x86/amd: pmc: Always write to the STB

[Mario Limonciello]

The kernel parameter `enable_stb` currently gates the access to the STB
from debugfs and also controls whether the kernel writes events to the
STB.

Even if not accessing STB data from the kernel it's useful to have this
data stored to review the STB. So in suspend/resume always write it.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/platform/x86/amd/pmc.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/platform/x86/amd/pmc.c b/drivers/platform/x86/amd/pmc.c
index 39e6ab88861d..fba42036682d 100644
--- a/drivers/platform/x86/amd/pmc.c
+++ b/drivers/platform/x86/amd/pmc.c
@@ -701,11 +701,9 @@ static void amd_pmc_s2idle_prepare(void)
 		return;
 	}
 
-	if (enable_stb) {
-		rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_S2IDLE_PREPARE);
-		if (rc)
-			dev_err(pdev->dev, "error writing to STB: %d\n", rc);
-	}
+	rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_S2IDLE_PREPARE);
+	if (rc)
+		dev_err(pdev->dev, "error writing to STB: %d\n", rc);
 }
 
 static void amd_pmc_s2idle_restore(void)
@@ -725,11 +723,9 @@ static void amd_pmc_s2idle_restore(void)
 	/* Dump the IdleMask to see the blockers */
 	amd_pmc_idlemask_read(pdev, pdev->dev, NULL);
 
-	if (enable_stb) {
-		rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_S2IDLE_RESTORE);
-		if (rc)
-			dev_err(pdev->dev, "error writing to STB: %d\n", rc);
-	}
+	rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_S2IDLE_RESTORE);
+	if (rc)
+		dev_err(pdev->dev, "error writing to STB: %d\n", rc);
 
 	/* Notify on failed entry */
 	amd_pmc_validate_deepest(pdev);
-- 
2.34.1

[PATCH v2 4/4] platform/x86/amd: pmc: Add an extra STB message for entering s2idle

[Mario Limonciello]

The `enter` callback is run right before the cores are put into HLT.
This will allow checking synchronization problems with other software
that writes into the STB.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/platform/x86/amd/pmc.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/platform/x86/amd/pmc.c b/drivers/platform/x86/amd/pmc.c
index fba42036682d..33300db461d1 100644
--- a/drivers/platform/x86/amd/pmc.c
+++ b/drivers/platform/x86/amd/pmc.c
@@ -41,6 +41,7 @@
 #define AMD_PMC_STB_PMI_0		0x03E30600
 #define AMD_PMC_STB_S2IDLE_PREPARE	0xC6000001
 #define AMD_PMC_STB_S2IDLE_RESTORE	0xC6000002
+#define AMD_PMC_STB_S2IDLE_ENTER	0xC6000003
 
 /* STB S2D(Spill to DRAM) has different message port offset */
 #define STB_SPILL_TO_DRAM		0xBE
@@ -706,6 +707,16 @@ static void amd_pmc_s2idle_prepare(void)
 		dev_err(pdev->dev, "error writing to STB: %d\n", rc);
 }
 
+static void amd_pmc_s2idle_enter(void)
+{
+	struct amd_pmc_dev *pdev = &pmc;
+	int rc;
+
+	rc = amd_pmc_write_stb(pdev, AMD_PMC_STB_S2IDLE_ENTER);
+	if (rc)
+		dev_err(pdev->dev, "error writing to STB: %d\n", rc);
+}
+
 static void amd_pmc_s2idle_restore(void)
 {
 	struct amd_pmc_dev *pdev = &pmc;
@@ -733,6 +744,7 @@ static void amd_pmc_s2idle_restore(void)
 
 static struct acpi_s2idle_dev_ops amd_pmc_s2idle_dev_ops = {
 	.prepare = amd_pmc_s2idle_prepare,
+	.enter = amd_pmc_s2idle_enter,
 	.restore = amd_pmc_s2idle_restore,
 };
 #endif
-- 
2.34.1

Re: [PATCH v2 1/4] ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops

[Rafael J. Wysocki]

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?

> 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.

>  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
>

Re: [PATCH v2 1/4] ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops

[Limonciello, Mario]

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
>>

Re: [PATCH v2 1/4] ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops

[Rafael J. Wysocki]

On Mon, Aug 29, 2022 at 4:32 PM Limonciello, Mario
<mario.limonciello@amd.com> wrote:
>
> 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.

I meant directly, without adding new driver callbacks.  Adding
callbacks for debug only seems a bit excessive.

But I guess the problem is that you need to ask the PMC about
something then, don't you?

> >
> >> 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?

acpi_s2idle_check() or similar.

> >
> >>   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();
> >>          }
> >>
> >> --

Re: [PATCH v2 1/4] ACPI: s2idle: Add a new ->enter() callback for platform_s2idle_ops

[Limonciello, Mario]

On 8/29/2022 09:40, Rafael J. Wysocki wrote:
> On Mon, Aug 29, 2022 at 4:32 PM Limonciello, Mario
> <mario.limonciello@amd.com> wrote:
>>
>> 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.
> 
> I meant directly, without adding new driver callbacks.  Adding
> callbacks for debug only seems a bit excessive.
> 
> But I guess the problem is that you need to ask the PMC about
> something then, don't you?

Yeah, that's exactly it.  The code changes there won't make sense 
generically.  I suppose it's possible to make a global symbol and only 
call it in the AMD case, but this approach should be a lot cleaner.

I did CC you in the other 3 patches in the series (in platform-x86) so 
you can see exactly how it's used.  Patch 4/4 is the one that uses this.

https://patchwork.kernel.org/project/platform-driver-x86/patch/20220829132908.5254-5-mario.limonciello@amd.com/

> 
>>>
>>>> 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?
> 
> acpi_s2idle_check() or similar.

OK, will plan to change over to this name for v3.

> 
>>>
>>>>    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();
>>>>           }
>>>>
>>>> --