From: Mika Westerberg <email@example.com> To: "Rafael J. Wysocki" <firstname.lastname@example.org> Cc: "Rafael J. Wysocki" <email@example.com>, Bjorn Helgaas <firstname.lastname@example.org>, Len Brown <email@example.com>, Lukas Wunner <firstname.lastname@example.org>, Keith Busch <email@example.com>, Alex Williamson <firstname.lastname@example.org>, Alexandru Gagniuc <email@example.com>, ACPI Devel Maling List <firstname.lastname@example.org>, Linux PCI <email@example.com> 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 > <firstname.lastname@example.org> 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.
next prev parent 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
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