RE: [PATCH 1/4] ACPI / x86: Add support for LPS0 callback handler

["Limonciello, Mario" <Mario.Limonciello@amd.com>]

[Public]

> On Thu, 2022-03-10 at 09:17 -0600, Mario Limonciello wrote:
> > Currenty the latest thing run during a suspend to idle attempt is
> > the LPS0 `prepare_late` callback and the earliest thing is the
> > `resume_early` callback.
> >
> > There is a desire for the `amd-pmc` driver to suspend later in the
> > suspend process (ideally the very last thing), so create a callback
> > that it or any other driver can hook into to do this.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> > ---
> >  drivers/acpi/x86/s2idle.c | 76
> ++++++++++++++++++++++++++++++++++++++-
> >  include/linux/acpi.h      |  9 ++++-
> >  2 files changed, 83 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
> > index abc06e7f89d8..652dc2d75458 100644
> > --- a/drivers/acpi/x86/s2idle.c
> > +++ b/drivers/acpi/x86/s2idle.c
> > @@ -86,6 +86,16 @@ struct lpi_device_constraint_amd {
> >  	int min_dstate;
> >  };
> >
> > +struct lps0_callback_handler {
> > +	struct list_head list_node;
> > +	int (*prepare_late_callback)(void *context);
> > +	void (*restore_early_callback)(void *context);
> > +	void *context;
> > +};
> 
> Maybe put this in acpi.h

Wonderful suggestion, thanks!
I'll adopt this for v2 after some other feedback comes in on the approach.

> 
> ...
> 
> 
> > +
> > +static LIST_HEAD(lps0_callback_handler_head);
> > +static DEFINE_MUTEX(lps0_callback_handler_mutex);
> > +
> >  static struct lpi_constraints *lpi_constraints_table;
> >  static int lpi_constraints_table_size;
> >  static int rev_id;
> > @@ -444,6 +454,9 @@ static struct acpi_scan_handler lps0_handler = {
> >
> >  int acpi_s2idle_prepare_late(void)
> >  {
> > +	struct lps0_callback_handler *handler;
> > +	int rc = 0;
> > +
> >  	if (!lps0_device_handle || sleep_no_lps0)
> >  		return 0;
> >
> > @@ -474,14 +487,31 @@ int acpi_s2idle_prepare_late(void)
> >  		acpi_sleep_run_lps0_dsm(ACPI_LPS0_MS_ENTRY,
> >  				lps0_dsm_func_mask_microsoft,
> > lps0_dsm_guid_microsoft);
> >  	}
> > -	return 0;
> > +
> > +	mutex_lock(&lps0_callback_handler_mutex);
> > +	list_for_each_entry(handler, &lps0_callback_handler_head,
> list_node) {
> > +		rc = handler->prepare_late_callback(handler->context);
> > +		if (rc)
> > +			goto out;
> > +	}
> > +out:
> > +	mutex_unlock(&lps0_callback_handler_mutex);
> > +
> > +	return rc;
> >  }
> >
> >  void acpi_s2idle_restore_early(void)
> >  {
> > +	struct lps0_callback_handler *handler;
> > +
> >  	if (!lps0_device_handle || sleep_no_lps0)
> >  		return;
> >
> > +	mutex_lock(&lps0_callback_handler_mutex);
> > +	list_for_each_entry(handler, &lps0_callback_handler_head,
> list_node)
> > +		handler->restore_early_callback(handler->context);
> > +	mutex_unlock(&lps0_callback_handler_mutex);
> > +
> >  	/* Modern standby exit */
> >  	if (lps0_dsm_func_mask_microsoft > 0)
> >  		acpi_sleep_run_lps0_dsm(ACPI_LPS0_MS_EXIT,
> > @@ -524,4 +554,48 @@ void acpi_s2idle_setup(void)
> >  	s2idle_set_ops(&acpi_s2idle_ops_lps0);
> >  }
> >
> > +int acpi_register_lps0_callbacks(int (*prepare_late)(void *context),
> > +				 void (*restore_early)(void *context),
> > +				 void *context)
> 
> ... and just have "struct lps0_callback_handler *handler" be the argument
> here.
> 
> David
> 
> > +{
> > +	struct lps0_callback_handler *handler;
> > +
> > +	if (!lps0_device_handle || sleep_no_lps0)
> > +		return -ENODEV;
> > +
> > +	handler = kmalloc(sizeof(*handler), GFP_KERNEL);
> > +	if (!handler)
> > +		return -ENOMEM;
> > +	handler->prepare_late_callback = prepare_late;
> > +	handler->restore_early_callback = restore_early;
> > +	handler->context = context;
> > +
> > +	mutex_lock(&lps0_callback_handler_mutex);
> > +	list_add(&handler->list_node, &lps0_callback_handler_head);
> > +	mutex_unlock(&lps0_callback_handler_mutex);
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_register_lps0_callbacks);
> > +
> > +void acpi_unregister_lps0_callbacks(int (*prepare_late)(void *context),
> > +				    void (*restore_early)(void *context),
> > +				    void *context)
> > +{
> > +	struct lps0_callback_handler *handler;
> > +
> > +	mutex_lock(&lps0_callback_handler_mutex);
> > +	list_for_each_entry(handler, &lps0_callback_handler_head,
> list_node) {
> > +		if (handler->prepare_late_callback == prepare_late &&
> > +		    handler->restore_early_callback == restore_early &&
> > +		    handler->context == context) {
> > +			list_del(&handler->list_node);
> > +			kfree(handler);
> > +			break;
> > +		}
> > +	}
> > +	mutex_unlock(&lps0_callback_handler_mutex);
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_unregister_lps0_callbacks);
> > +
> >  #endif /* CONFIG_SUSPEND */
> > diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> > index 6274758648e3..cae0fde309f2 100644
> > --- a/include/linux/acpi.h
> > +++ b/include/linux/acpi.h
> > @@ -1023,7 +1023,14 @@ void acpi_os_set_prepare_extended_sleep(int
> (*func)(u8
> > sleep_state,
> >
> >  acpi_status acpi_os_prepare_extended_sleep(u8 sleep_state,
> >  					   u32 val_a, u32 val_b);
> > -
> > +#ifdef CONFIG_X86
> > +int acpi_register_lps0_callbacks(int (*prepare_late)(void *context),
> > +				 void (*restore_early)(void *context),
> > +				 void *context);
> > +void acpi_unregister_lps0_callbacks(int (*prepare_late)(void *context),
> > +				    void (*restore_early)(void *context),
> > +				    void *context);
> > +#endif /* CONFIG_X86 */
> >  #ifndef CONFIG_IA64
> >  void arch_reserve_mem_area(acpi_physical_address addr, size_t size);
> >  #else