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

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Date:   Fri, 11 Aug 2017 06:13:07 +0000
From:   "Zheng, Lv" <lv.zheng@...el.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
CC:     Linux ACPI <linux-acpi@...r.kernel.org>,
        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,

> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> Subject: Re: [PATCH 2/3] ACPICA: Make it possible to enable runtime GPEs earlier
> 
> On Thursday, August 10, 2017 3:52:05 AM CEST Zheng, Lv wrote:
> > 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?
> 
> Even if it is shared, the current code will not enable it if it sees
> ACPI_GPE_CAN_WAKE set.
> 
> We can change that logic, but that should be a separate patch IMO and
> this is not related to the problem at hand.

OK, I see.
We can enhance that on top of these fixes.

Thanks,
Lv