linux-kernel - RE: [PATCH 2/3] ACPICA: Make it possible to enable runtime GPEs earlier

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Date:   Thu, 10 Aug 2017 01:52:05 +0000
From:   "Zheng, Lv" <lv.zheng@...el.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>
CC:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Moore, Robert" <robert.moore@...el.com>
Subject: RE: [PATCH 2/3] ACPICA: Make it possible to enable runtime GPEs
 earlier

Hi, Rafael

For this patch, I have a concern.

> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> Subject: [PATCH 2/3] ACPICA: Make it possible to enable runtime GPEs earlier
> 
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Runtime GPEs have corresponding _Lxx/_Exx methods and are enabled
> automatically during the initialization of the ACPI subsystem through
> acpi_update_all_gpes() with the assumption that acpi_setup_gpe_for_wake()
> will be called in advance for all of the GPEs pointed to by _PRW
> objects in the namespace that may be affected by acpi_update_all_gpes().
> That is, acpi_ev_initialize_gpe_block() can only be called for a GPE
> block after acpi_setup_gpe_for_wake() has been called for all of the
> _PRW (wakeup) GPEs in it.
> 
> The platform firmware on some systems, however, expects GPEs to be
> enabled before the enumeration of devices which is when
> acpi_setup_gpe_for_wake() is called and that goes against the above
> assumption.
> 
> For this reason, introduce a new flag to be set by
> acpi_ev_initialize_gpe_block() when automatically enabling a GPE
> to indicate to acpi_setup_gpe_for_wake() that it needs to drop the
> reference to the GPE coming from acpi_ev_initialize_gpe_block()
> and modify acpi_setup_gpe_for_wake() accordingly.  These changes
> allow acpi_setup_gpe_for_wake() and acpi_ev_initialize_gpe_block()
> to be invoked in any order.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/acpica/evgpeblk.c |    2 ++
>  drivers/acpi/acpica/evxfgpe.c  |    8 ++++++++
>  include/acpi/actypes.h         |    3 ++-
>  3 files changed, 12 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/acpi/acpica/evgpeblk.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/acpica/evgpeblk.c
> +++ linux-pm/drivers/acpi/acpica/evgpeblk.c
> @@ -496,6 +496,8 @@ acpi_ev_initialize_gpe_block(struct acpi
>  				continue;
>  			}
> 
> +			gpe_event_info->flags |= ACPI_GPE_AUTO_ENABLED;
> +
>  			if (event_status & ACPI_EVENT_FLAG_STATUS_SET) {
>  				ACPI_INFO(("GPE 0x%02X active on init",
>  					   gpe_number));
> Index: linux-pm/include/acpi/actypes.h
> ===================================================================
> --- linux-pm.orig/include/acpi/actypes.h
> +++ linux-pm/include/acpi/actypes.h
> @@ -783,7 +783,7 @@ typedef u32 acpi_event_status;
>   *   |  | | |  +-- Type of dispatch:to method, handler, notify, or none
>   *   |  | | +----- Interrupt type: edge or level triggered
>   *   |  | +------- Is a Wake GPE
> - *   |  +--------- Is GPE masked by the software GPE masking mechanism
> + *   |  +--------- Has been enabled automatically at init time
>   *   +------------ <Reserved>
>   */
>  #define ACPI_GPE_DISPATCH_NONE          (u8) 0x00
> @@ -799,6 +799,7 @@ typedef u32 acpi_event_status;
>  #define ACPI_GPE_XRUPT_TYPE_MASK        (u8) 0x08
> 
>  #define ACPI_GPE_CAN_WAKE               (u8) 0x10
> +#define ACPI_GPE_AUTO_ENABLED           (u8) 0x20
> 
>  /*
>   * Flags for GPE and Lock interfaces
> Index: linux-pm/drivers/acpi/acpica/evxfgpe.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/acpica/evxfgpe.c
> +++ linux-pm/drivers/acpi/acpica/evxfgpe.c
> @@ -435,6 +435,14 @@ acpi_setup_gpe_for_wake(acpi_handle wake
>  		 */
>  		gpe_event_info->flags =
>  		    (ACPI_GPE_DISPATCH_NOTIFY | ACPI_GPE_LEVEL_TRIGGERED);
> +	} else if (gpe_event_info->flags & ACPI_GPE_AUTO_ENABLED) {
> +		/*
> +		 * A reference to this GPE has been added during the GPE block
> +		 * initialization, so drop it now to prevent the GPE from being
> +		 * permanently enabled and clear its ACPI_GPE_AUTO_ENABLED flag.
> +		 */
> +		(void)acpi_ev_remove_gpe_reference(gpe_event_info);
> +		gpe_event_info->flags &= ~ACPI_GPE_AUTO_ENABLED;

The problem is if the GPE is shared, how can we know decrement reference
once can sufficiently convert it into wakeup dispatcher owned GPE?

Thanks and best regards
Lv