[RFC PATCH 0/3] Skip thaw sequence for all devices, not just amdgpu

[RFC PATCH 0/3] Skip thaw sequence for all devices, not just amdgpu

[Mario Limonciello (AMD)]

As part of looking at the hibernate code recently again I was considering
whether we really need the thaw stage at all when things are working well.

So I wanted to explore what breaks if we just skip it.  This should speed
up the S4 sequence since nothing needs to resume.

If we do this we can drop the special cases in amdgpu and the exported
symbols too.

Mario Limonciello (3):
  PM: hibernate: Nominally skip thaw sequence for all devices
  drm/amd: Drop special cases for thaw() callback
  PM: Drop pm_hibernate_is_recovering() and
    pm_hibernation_mode_is_suspend()

 drivers/base/power/main.c               | 20 ++++++--------------
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c |  4 ----
 include/linux/suspend.h                 |  8 --------
 kernel/power/hibernate.c                | 24 ++++++++++--------------
 kernel/power/user.c                     |  3 +++
 5 files changed, 19 insertions(+), 40 deletions(-)

-- 
2.43.0

[RFC PATCH 1/3] PM: hibernate: Nominally skip thaw sequence for all devices

[Mario Limonciello (AMD)]

From: Mario Limonciello <mario.limonciello@amd.com>

After the hibernation snapshot is created all devices will have
their thaw() callback called before the next stage.  For the most
common scenarios of hibernation this is not necessary because the
device will be powered off anyway.

If the hibernation snapshot was successfully created skip thawing
devices until it's needed for userspace created hibernation image
or hybrid sleep. To accomplish this use PMSG_INVALID in
hibernation_snapshot() and set the dpm functions to skip running.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/base/power/main.c |  6 ++++++
 kernel/power/hibernate.c  | 13 ++++++++++---
 kernel/power/user.c       |  3 +++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 8179fd53171dc..58f5270a173e8 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1143,6 +1143,9 @@ void dpm_resume(pm_message_t state)
 	struct device *dev;
 	ktime_t starttime = ktime_get();
 
+	if (state.event == PM_EVENT_INVALID)
+		return;
+
 	trace_suspend_resume(TPS("dpm_resume"), state.event, true);
 
 	pm_transition = state;
@@ -1245,6 +1248,9 @@ void dpm_complete(pm_message_t state)
 {
 	struct list_head list;
 
+	if (state.event == PM_EVENT_INVALID)
+		return;
+
 	trace_suspend_resume(TPS("dpm_complete"), state.event, true);
 
 	INIT_LIST_HEAD(&list);
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index aadf82f57e868..7af2e392c574a 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -480,13 +480,14 @@ int hibernation_snapshot(int platform_mode)
 	if (error || !in_suspend)
 		swsusp_free();
 
-	msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE;
+	msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_INVALID) : PMSG_RESTORE;
 	dpm_resume(msg);
 
-	if (error || !in_suspend)
+	if (error || !in_suspend) {
 		pm_restore_gfp_mask();
+		console_resume_all();
+	}
 
-	console_resume_all();
 	dpm_complete(msg);
 
  Close:
@@ -707,7 +708,13 @@ static void power_down(void)
 
 #ifdef CONFIG_SUSPEND
 	if (hibernation_mode == HIBERNATION_SUSPEND) {
+		/* recover from hibernation_snapshot() */
+		dpm_resume(PMSG_THAW);
+		console_resume_all();
+		dpm_complete(PMSG_THAW);
 		pm_restore_gfp_mask();
+
+		/* run suspend sequence */
 		error = suspend_devices_and_enter(mem_sleep_current);
 		if (!error)
 			goto exit;
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 3f9e3efb9f6e7..d70c963b1ba88 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -310,6 +310,9 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 		pm_restore_gfp_mask();
 		error = hibernation_snapshot(data->platform_support);
 		if (!error) {
+			dpm_resume(PMSG_THAW);
+			console_resume_all();
+			dpm_complete(PMSG_THAW);
 			error = put_user(in_suspend, (int __user *)arg);
 			data->ready = !freezer_test_done && !error;
 			freezer_test_done = false;
-- 
2.43.0

[RFC PATCH 2/3] drm/amd: Drop special cases for thaw() callback

[Mario Limonciello (AMD)]

From: Mario Limonciello <mario.limonciello@amd.com>

The special cases to use pm_hibernate_is_recovering() and
pm_hibernation_mode_is_suspend() were for an optimization to avoid
turning the display on and moving memory around when the system
was about to hibernate anyway.

As the hibernate core skips thaw() unless it's necessary drop them.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 6d547f4e4bafc..4a37c3e517a9f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -2671,10 +2671,6 @@ static int amdgpu_pmops_thaw(struct device *dev)
 {
 	struct drm_device *drm_dev = dev_get_drvdata(dev);
 
-	/* do not resume device if it's normal hibernation */
-	if (!pm_hibernate_is_recovering() && !pm_hibernation_mode_is_suspend())
-		return 0;
-
 	return amdgpu_device_resume(drm_dev, true);
 }
 
-- 
2.43.0

[RFC PATCH 3/3] PM: Drop pm_hibernate_is_recovering() and pm_hibernation_mode_is_suspend()

[Mario Limonciello (AMD)]

From: Mario Limonciello <mario.limonciello@amd.com>

All consumers in the kernel of pm_hibernate_is_recovering() and
pm_hibernation_mode_is_suspend() have been dropped.  Remove the symbols.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/base/power/main.c | 14 --------------
 include/linux/suspend.h   |  8 --------
 kernel/power/hibernate.c  | 11 -----------
 3 files changed, 33 deletions(-)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 58f5270a173e8..e2f23e62abb18 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -62,20 +62,6 @@ static pm_message_t pm_transition;
 static DEFINE_MUTEX(async_wip_mtx);
 static int async_error;
 
-/**
- * pm_hibernate_is_recovering - if recovering from hibernate due to error.
- *
- * Used to query if dev_pm_ops.thaw() is called for normal hibernation case or
- * recovering from some error.
- *
- * Return: true for error case, false for normal case.
- */
-bool pm_hibernate_is_recovering(void)
-{
-	return pm_transition.event == PM_EVENT_RECOVER;
-}
-EXPORT_SYMBOL_GPL(pm_hibernate_is_recovering);
-
 static const char *pm_verb(int event)
 {
 	switch (event) {
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 348831cdb60e4..f305fcc7a2cdc 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -420,12 +420,6 @@ static inline int hibernate_quiet_exec(int (*func)(void *data), void *data) {
 }
 #endif /* CONFIG_HIBERNATION */
 
-#if defined(CONFIG_HIBERNATION) && defined(CONFIG_SUSPEND)
-bool pm_hibernation_mode_is_suspend(void);
-#else
-static inline bool pm_hibernation_mode_is_suspend(void) { return false; }
-#endif
-
 int arch_resume_nosmt(void);
 
 #ifdef CONFIG_HIBERNATION_SNAPSHOT_DEV
@@ -486,7 +480,6 @@ extern unsigned int lock_system_sleep(void);
 extern void unlock_system_sleep(unsigned int);
 
 extern bool pm_sleep_transition_in_progress(void);
-bool pm_hibernate_is_recovering(void);
 
 #else /* !CONFIG_PM_SLEEP */
 
@@ -520,7 +513,6 @@ static inline unsigned int lock_system_sleep(void) { return 0; }
 static inline void unlock_system_sleep(unsigned int flags) {}
 
 static inline bool pm_sleep_transition_in_progress(void) { return false; }
-static inline bool pm_hibernate_is_recovering(void) { return false; }
 
 #endif /* !CONFIG_PM_SLEEP */
 
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 7af2e392c574a..ec02a8be20b30 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -80,17 +80,6 @@ static const struct platform_hibernation_ops *hibernation_ops;
 
 static atomic_t hibernate_atomic = ATOMIC_INIT(1);
 
-#ifdef CONFIG_SUSPEND
-/**
- * pm_hibernation_mode_is_suspend - Check if hibernation has been set to suspend
- */
-bool pm_hibernation_mode_is_suspend(void)
-{
-	return hibernation_mode == HIBERNATION_SUSPEND;
-}
-EXPORT_SYMBOL_GPL(pm_hibernation_mode_is_suspend);
-#endif
-
 bool hibernate_acquire(void)
 {
 	return atomic_add_unless(&hibernate_atomic, -1, 0);
-- 
2.43.0

Re: [RFC PATCH 1/3] PM: hibernate: Nominally skip thaw sequence for all devices

[Rafael J. Wysocki]

On Mon, Oct 13, 2025 at 7:48 PM Mario Limonciello (AMD)
<superm1@kernel.org> wrote:
>
> From: Mario Limonciello <mario.limonciello@amd.com>
>
> After the hibernation snapshot is created all devices will have
> their thaw() callback called before the next stage.  For the most
> common scenarios of hibernation this is not necessary because the
> device will be powered off anyway.

And how exactly is the image going to be saved?

It is only in memory when the "thaw" callbacks are invoked.

> If the hibernation snapshot was successfully created skip thawing
> devices until it's needed for userspace created hibernation image
> or hybrid sleep. To accomplish this use PMSG_INVALID in
> hibernation_snapshot() and set the dpm functions to skip running.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>  drivers/base/power/main.c |  6 ++++++
>  kernel/power/hibernate.c  | 13 ++++++++++---
>  kernel/power/user.c       |  3 +++
>  3 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 8179fd53171dc..58f5270a173e8 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1143,6 +1143,9 @@ void dpm_resume(pm_message_t state)
>         struct device *dev;
>         ktime_t starttime = ktime_get();
>
> +       if (state.event == PM_EVENT_INVALID)
> +               return;
> +
>         trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>
>         pm_transition = state;
> @@ -1245,6 +1248,9 @@ void dpm_complete(pm_message_t state)
>  {
>         struct list_head list;
>
> +       if (state.event == PM_EVENT_INVALID)
> +               return;
> +
>         trace_suspend_resume(TPS("dpm_complete"), state.event, true);
>
>         INIT_LIST_HEAD(&list);
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index aadf82f57e868..7af2e392c574a 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -480,13 +480,14 @@ int hibernation_snapshot(int platform_mode)
>         if (error || !in_suspend)
>                 swsusp_free();
>
> -       msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE;
> +       msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_INVALID) : PMSG_RESTORE;
>         dpm_resume(msg);
>
> -       if (error || !in_suspend)
> +       if (error || !in_suspend) {
>                 pm_restore_gfp_mask();
> +               console_resume_all();
> +       }
>
> -       console_resume_all();
>         dpm_complete(msg);
>
>   Close:
> @@ -707,7 +708,13 @@ static void power_down(void)
>
>  #ifdef CONFIG_SUSPEND
>         if (hibernation_mode == HIBERNATION_SUSPEND) {
> +               /* recover from hibernation_snapshot() */
> +               dpm_resume(PMSG_THAW);
> +               console_resume_all();
> +               dpm_complete(PMSG_THAW);
>                 pm_restore_gfp_mask();
> +
> +               /* run suspend sequence */
>                 error = suspend_devices_and_enter(mem_sleep_current);
>                 if (!error)
>                         goto exit;
> diff --git a/kernel/power/user.c b/kernel/power/user.c
> index 3f9e3efb9f6e7..d70c963b1ba88 100644
> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -310,6 +310,9 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
>                 pm_restore_gfp_mask();
>                 error = hibernation_snapshot(data->platform_support);
>                 if (!error) {
> +                       dpm_resume(PMSG_THAW);
> +                       console_resume_all();
> +                       dpm_complete(PMSG_THAW);
>                         error = put_user(in_suspend, (int __user *)arg);
>                         data->ready = !freezer_test_done && !error;
>                         freezer_test_done = false;
> --
> 2.43.0
>

Re: [RFC PATCH 1/3] PM: hibernate: Nominally skip thaw sequence for all devices

[Mario Limonciello]

On 10/13/25 12:58 PM, Rafael J. Wysocki wrote:
> On Mon, Oct 13, 2025 at 7:48 PM Mario Limonciello (AMD)
> <superm1@kernel.org> wrote:
>>
>> From: Mario Limonciello <mario.limonciello@amd.com>
>>
>> After the hibernation snapshot is created all devices will have
>> their thaw() callback called before the next stage.  For the most
>> common scenarios of hibernation this is not necessary because the
>> device will be powered off anyway.
> 
> And how exactly is the image going to be saved?
> 
> It is only in memory when the "thaw" callbacks are invoked.

Ah; right.

I suppose one option would be to thaw "just" the backing device, but 
this could turn into a relatively complex mess because it would have 
relationships (parent/child or device link) to other devices that need 
to thaw too then.

> 
>> If the hibernation snapshot was successfully created skip thawing
>> devices until it's needed for userspace created hibernation image
>> or hybrid sleep. To accomplish this use PMSG_INVALID in
>> hibernation_snapshot() and set the dpm functions to skip running.
>>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>>   drivers/base/power/main.c |  6 ++++++
>>   kernel/power/hibernate.c  | 13 ++++++++++---
>>   kernel/power/user.c       |  3 +++
>>   3 files changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>> index 8179fd53171dc..58f5270a173e8 100644
>> --- a/drivers/base/power/main.c
>> +++ b/drivers/base/power/main.c
>> @@ -1143,6 +1143,9 @@ void dpm_resume(pm_message_t state)
>>          struct device *dev;
>>          ktime_t starttime = ktime_get();
>>
>> +       if (state.event == PM_EVENT_INVALID)
>> +               return;
>> +
>>          trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>>
>>          pm_transition = state;
>> @@ -1245,6 +1248,9 @@ void dpm_complete(pm_message_t state)
>>   {
>>          struct list_head list;
>>
>> +       if (state.event == PM_EVENT_INVALID)
>> +               return;
>> +
>>          trace_suspend_resume(TPS("dpm_complete"), state.event, true);
>>
>>          INIT_LIST_HEAD(&list);
>> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
>> index aadf82f57e868..7af2e392c574a 100644
>> --- a/kernel/power/hibernate.c
>> +++ b/kernel/power/hibernate.c
>> @@ -480,13 +480,14 @@ int hibernation_snapshot(int platform_mode)
>>          if (error || !in_suspend)
>>                  swsusp_free();
>>
>> -       msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE;
>> +       msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_INVALID) : PMSG_RESTORE;
>>          dpm_resume(msg);
>>
>> -       if (error || !in_suspend)
>> +       if (error || !in_suspend) {
>>                  pm_restore_gfp_mask();
>> +               console_resume_all();
>> +       }
>>
>> -       console_resume_all();
>>          dpm_complete(msg);
>>
>>    Close:
>> @@ -707,7 +708,13 @@ static void power_down(void)
>>
>>   #ifdef CONFIG_SUSPEND
>>          if (hibernation_mode == HIBERNATION_SUSPEND) {
>> +               /* recover from hibernation_snapshot() */
>> +               dpm_resume(PMSG_THAW);
>> +               console_resume_all();
>> +               dpm_complete(PMSG_THAW);
>>                  pm_restore_gfp_mask();
>> +
>> +               /* run suspend sequence */
>>                  error = suspend_devices_and_enter(mem_sleep_current);
>>                  if (!error)
>>                          goto exit;
>> diff --git a/kernel/power/user.c b/kernel/power/user.c
>> index 3f9e3efb9f6e7..d70c963b1ba88 100644
>> --- a/kernel/power/user.c
>> +++ b/kernel/power/user.c
>> @@ -310,6 +310,9 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
>>                  pm_restore_gfp_mask();
>>                  error = hibernation_snapshot(data->platform_support);
>>                  if (!error) {
>> +                       dpm_resume(PMSG_THAW);
>> +                       console_resume_all();
>> +                       dpm_complete(PMSG_THAW);
>>                          error = put_user(in_suspend, (int __user *)arg);
>>                          data->ready = !freezer_test_done && !error;
>>                          freezer_test_done = false;
>> --
>> 2.43.0
>>

Re: [RFC PATCH 1/3] PM: hibernate: Nominally skip thaw sequence for all devices

[Rafael J. Wysocki]

On Mon, Oct 13, 2025 at 8:27 PM Mario Limonciello <superm1@kernel.org> wrote:
>
> On 10/13/25 12:58 PM, Rafael J. Wysocki wrote:
> > On Mon, Oct 13, 2025 at 7:48 PM Mario Limonciello (AMD)
> > <superm1@kernel.org> wrote:
> >>
> >> From: Mario Limonciello <mario.limonciello@amd.com>
> >>
> >> After the hibernation snapshot is created all devices will have
> >> their thaw() callback called before the next stage.  For the most
> >> common scenarios of hibernation this is not necessary because the
> >> device will be powered off anyway.
> >
> > And how exactly is the image going to be saved?
> >
> > It is only in memory when the "thaw" callbacks are invoked.
>
> Ah; right.
>
> I suppose one option would be to thaw "just" the backing device, but
> this could turn into a relatively complex mess because it would have
> relationships (parent/child or device link) to other devices that need
> to thaw too then.

Right and that's exactly why everything is thawed.