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

["David E. Box" <david.e.box@linux.intel.com>]

Hi Mario,

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

...


> +
> +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