From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
"Limonciello, Mario" <mario.limonciello@amd.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Len Brown <lenb@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Mehta Sanju <Sanju.Mehta@amd.com>, Lukas Wunner <lukas@wunner.de>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] PCI/ACPI: PCI/ACPI: Validate devices with power resources support D3
Date: Wed, 11 Jan 2023 11:56:05 +0100 [thread overview]
Message-ID: <CAJZ5v0gwLU2rsUWga+aEyWtXb=CHx2wqbrXX1hc+M_Po64a11A@mail.gmail.com> (raw)
In-Reply-To: <20230110205513.GA1608269@bhelgaas>
On Tue, Jan 10, 2023 at 9:55 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Mon, Jan 02, 2023 at 05:59:36PM +0100, Rafael J. Wysocki wrote:
> > On Monday, January 2, 2023 5:34:19 PM CET Rafael J. Wysocki wrote:
> > ...
>
> > > I don't really think that Root Port support is required for a bridge below
> > > a Root Port if that bridge itself is power-manageable via ACPI. Moreover,
> > > I don't think that the _S0W of a Root Port has any bearing on devices below
> > > it that have their own _S0W.
> > >
> > > So what we really want appears to be to evaluate _S0W for the target bridge,
> > > regardless of whether or not it is a Root Port, and return 'false' if that
> > > produces D2 or a shallower power state. Otherwise, we can do what we've
> > > done so far.
>
> > +bool acpi_dev_no_wakeup_from_d3(struct acpi_device *adev)
> > +{
> > + unsigned long long state;
> > + acpi_status status;
> > +
> > + status = acpi_evaluate_integer(adev->handle, "_S0W", NULL, &state);
> > + return ACPI_SUCCESS(status) && state < ACPI_STATE_D3_HOT;
>
> This returns "false" (i.e., "yes, device can signal wakeup from D3")
> if _S0W doesn't exist. Is that right?
Yes, it is.
The reason why I did it that way was because the bridge cannot signal
wakeup from D3 if both the following conditions take place:
1. There is _S0W and it can be evaluated successfully.
2. _S0W produces D2 or a shallower power state.
In particular, if 1 is not the case, it is still not clear whether or
not the bridge can signal wakeup from D3 and additional checks are
needed.
> I think this might be less confusing as:
>
> bool acpi_dev_can_wake_from_d3(struct acpi_device *adev)
> {
> status = acpi_evaluate_integer(adev->handle, "_S0W", NULL, &state);
> return ACPI_SUCCESS(status) && state >= ACPI_STATE_D3_HOT;
> }
So I don't think the above will work, because
!acpi_dev_can_wake_from_d3(adev) is also true if _S0W is not present,
for example, in which case acpi_pci_bridge_d3() should not return
'false' right away.
However, the additional function can simply return the value produced
by _S0W or ACPI_STATE_UNKNOWN on all errors and its caller can do the
checks as needed which is done here:
https://patchwork.kernel.org/project/linux-acpi/patch/5659681.DvuYhMxLoT@kreacher/
(posted as a proper patch, because I wanted patchwork to pick it up).
I've also picked up the idea of using rpadev for representing the ACPI
companion of the Root Port in acpi_pci_bridge_d3().
Cheers!
next prev parent reply other threads:[~2023-01-11 10:57 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-31 22:33 [PATCH v5] PCI/ACPI: PCI/ACPI: Validate devices with power resources support D3 Mario Limonciello
2022-11-11 17:41 ` Bjorn Helgaas
2022-11-11 18:58 ` Limonciello, Mario
2022-11-11 21:42 ` Bjorn Helgaas
2022-11-14 15:33 ` Rafael J. Wysocki
2022-11-14 15:37 ` Limonciello, Mario
2022-11-14 16:54 ` Bjorn Helgaas
2022-11-16 0:37 ` Bjorn Helgaas
2022-11-16 2:31 ` Limonciello, Mario
2022-11-16 12:00 ` Rafael J. Wysocki
2022-11-16 23:28 ` Bjorn Helgaas
2022-11-17 17:01 ` Rafael J. Wysocki
2022-11-17 22:16 ` Bjorn Helgaas
2022-11-18 13:16 ` Rafael J. Wysocki
2022-11-18 20:23 ` Bjorn Helgaas
2022-11-18 21:13 ` Rafael J. Wysocki
2022-11-21 14:33 ` Rafael J. Wysocki
2022-11-21 22:17 ` Bjorn Helgaas
2023-01-02 16:34 ` Rafael J. Wysocki
2023-01-02 16:59 ` Rafael J. Wysocki
2023-01-03 22:44 ` Limonciello, Mario
2023-01-10 18:02 ` Rafael J. Wysocki
2023-01-10 20:55 ` Bjorn Helgaas
2023-01-11 10:56 ` Rafael J. Wysocki [this message]
2023-01-12 20:13 ` Bjorn Helgaas
2023-01-11 10:38 ` [PATCH v3] PCI / ACPI: PM: Take _S0W of the target bridge into account in acpi_pci_bridge_d3(() Rafael J. Wysocki
2023-01-12 20:21 ` Bjorn Helgaas
2023-01-12 20:31 ` Rafael J. Wysocki
2023-01-12 20:51 ` [PATCH v4] " Rafael J. Wysocki
2023-01-12 22:01 ` Bjorn Helgaas
2023-01-12 22:09 ` Limonciello, Mario
2023-01-12 22:40 ` Bjorn Helgaas
2023-01-12 22:45 ` Limonciello, Mario
2023-01-13 17:51 ` Bjorn Helgaas
2023-01-13 17:53 ` Limonciello, Mario
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