Linux-ACPI Archive on lore.kernel.org
 help / color / Atom feed
From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Bjorn Helgaas <helgaas@kernel.org>, Len Brown <lenb@kernel.org>,
	Lukas Wunner <lukas@wunner.de>,
	Keith Busch <keith.busch@intel.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Alexandru Gagniuc <mr.nuke.me@gmail.com>,
	ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
	Linux PCI <linux-pci@vger.kernel.org>
Subject: Re: [PATCH v2 1/3] PCI / ACPI: Use cached ACPI device state to get PCI device power state
Date: Tue, 25 Jun 2019 13:08:51 +0300
Message-ID: <20190625100851.GB2640@lahna.fi.intel.com> (raw)
In-Reply-To: <CAJZ5v0gca0ey-NonUS4vgsv-kXwvnUzhGcDJpVotwscU3wc-nQ@mail.gmail.com>

On Tue, Jun 25, 2019 at 12:00:57PM +0200, Rafael J. Wysocki wrote:
> On Tue, Jun 25, 2019 at 11:46 AM Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
> >
> > On Mon, Jun 24, 2019 at 01:14:47PM +0200, Rafael J. Wysocki wrote:
> > > > The problem here is that acpi_device_get_power() really only should be
> > > > used for two purposes: (1) To initialize adev->power.state, or to
> > > > update it via acpi_device_update_power(), and (2) by the
> > > > "real_power_state" sysfs attribute (of ACPI device objects).  The
> > > > adev->power.state value should be used anywhere else, in principle, so
> > > > the Mika's patch is correct.
> > >
> > > Well, it is an improvement, but it is not sufficient.
> > >
> > > > [Note that adev->power.state cannot be updated after calling
> > > > acpi_device_get_power() to the value returned by it without updating
> > > > the reference counters of the power resources that are "on" *exactly*
> > > > because of the problem at hand here.]
> > >
> > > That is obviously correct, but ->
> > >
> > > > > but that's just an idle thought, not a suggestion.
> > > >
> > > > After the initialization of the ACPI subsystem, the authoritative
> > > > source of the ACPI device power state information is
> > > > adev->power.state.  The ACPI subsystem is expected to update this
> > > > value as needed going forward (including system-wide transitions like
> > > > resume from S3).
> > >
> > > -> the "resume from S3 or hibernation" case needs special handling, because
> > > in that case the device power state need not reflect the information the ACPI
> > > subsystem has.  That only matters if adev->power.state is ACPI_STATE_D0 and
> > > the device is actually *not* in D0, because in that case acpi_device_set_power()
> > > will not work.
> >
> > I guess you are talking about the special-cased devices that we leave in
> > D0 when system suspend (via firmware) is entered?
> >
> > > So that case is not covered currently (it should be rare in practice,
> > > though, if it happens at all), so something like the patch below (untested) may
> > > be needed in addition to the Mika's patch.
> >
> > Looks good to me.
> 
> I actually decided to address this issue in acpi_device_set_power() as
> it may affect devices beyond PCI in principle.  I will send a patch
> for that shortly.

Thanks!

> > > Still, there is also the "power state not matching" case in pci_pm_complete() that's
> > > need to be covered and the non-PCI ACPI PM has a similar issue in theory, so I
> > > need to think about this a bit more.
> >
> > Do you want me to hold off sending an updated version of the patch
> > series while we figure this one out or is it fine if I send it out now
> > and we can add further details on top?
> 
> It is independent of the other fix, so it can be sent now just fine IMO.

OK, I'll send it out in a minute.

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-18 16:18 [PATCH v2 0/3] PCI / ACPI: Handle sibling devices sharing power resources Mika Westerberg
2019-06-18 16:18 ` [PATCH v2 1/3] PCI / ACPI: Use cached ACPI device state to get PCI device power state Mika Westerberg
2019-06-19 21:28   ` Bjorn Helgaas
2019-06-20  8:27     ` Mika Westerberg
2019-06-20 13:16       ` Bjorn Helgaas
2019-06-20 13:37         ` Mika Westerberg
2019-06-20 14:15           ` Bjorn Helgaas
2019-06-21 10:32             ` Rafael J. Wysocki
2019-06-21 13:09               ` Bjorn Helgaas
2019-06-22  8:51                 ` Rafael J. Wysocki
2019-06-24 10:57                   ` Mika Westerberg
2019-06-24 11:14               ` Rafael J. Wysocki
2019-06-25  9:45                 ` Mika Westerberg
2019-06-25 10:00                   ` Rafael J. Wysocki
2019-06-25 10:08                     ` Mika Westerberg [this message]
2019-06-21 11:56   ` Rafael J. Wysocki
2019-06-24 10:58     ` Mika Westerberg
2019-06-18 16:18 ` [PATCH v2 2/3] ACPI / PM: Introduce concept of a _PR0 dependent device Mika Westerberg
2019-06-19 13:20   ` Rafael J. Wysocki
2019-06-19 13:34     ` Mika Westerberg
2019-06-18 16:18 ` [PATCH v2 3/3] PCI / ACPI: Add _PR0 dependent devices Mika Westerberg
2019-06-19 13:24 ` [PATCH v2 0/3] PCI / ACPI: Handle sibling devices sharing power resources Rafael J. Wysocki

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190625100851.GB2640@lahna.fi.intel.com \
    --to=mika.westerberg@linux.intel.com \
    --cc=alex.williamson@redhat.com \
    --cc=helgaas@kernel.org \
    --cc=keith.busch@intel.com \
    --cc=lenb@kernel.org \
    --cc=linux-acpi@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=lukas@wunner.de \
    --cc=mr.nuke.me@gmail.com \
    --cc=rafael@kernel.org \
    --cc=rjw@rjwysocki.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-ACPI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-acpi/0 linux-acpi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-acpi linux-acpi/ https://lore.kernel.org/linux-acpi \
		linux-acpi@vger.kernel.org linux-acpi@archiver.kernel.org
	public-inbox-index linux-acpi

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-acpi


AGPL code for this site: git clone https://public-inbox.org/ public-inbox