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Message-ID: <CAJZ5v0iba93EhQB2k3LMdb2YczndbRmF5WGRYHhnqCHq6TQJ0A@mail.gmail.com>
Date: Mon, 29 Jan 2024 16:05:42 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, "Rafael J. Wysocki" <rjw@...ysocki.net>,
"Rafael J. Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org, loongarch@...ts.linux.dev,
linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev, x86@...nel.org,
acpica-devel@...ts.linuxfoundation.org, linux-csky@...r.kernel.org,
linux-doc@...r.kernel.org, linux-ia64@...r.kernel.org,
linux-parisc@...r.kernel.org, Salil Mehta <salil.mehta@...wei.com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>, jianyong.wu@....com, justin.he@....com,
James Morse <james.morse@....com>
Subject: Re: [PATCH RFC v3 01/21] ACPI: Only enumerate enabled (or functional) devices
On Mon, Jan 29, 2024 at 3:55 PM Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> Hi Jonathan,
>
> On Fri, Jan 12, 2024 at 11:52:05AM +0000, Jonathan Cameron wrote:
> > On Thu, 11 Jan 2024 10:26:15 +0000
> > "Russell King (Oracle)" <linux@...linux.org.uk> wrote:
> > > @@ -2381,16 +2388,38 @@ EXPORT_SYMBOL_GPL(acpi_dev_clear_dependencies);
> > > * acpi_dev_ready_for_enumeration - Check if the ACPI device is ready for enumeration
> > > * @device: Pointer to the &struct acpi_device to check
> > > *
> > > - * Check if the device is present and has no unmet dependencies.
> > > + * Check if the device is functional or enabled and has no unmet dependencies.
> > > *
> > > - * Return true if the device is ready for enumeratino. Otherwise, return false.
> > > + * Return true if the device is ready for enumeration. Otherwise, return false.
> > > */
> > > bool acpi_dev_ready_for_enumeration(const struct acpi_device *device)
> > > {
> > > if (device->flags.honor_deps && device->dep_unmet)
> > > return false;
> > >
> > > - return acpi_device_is_present(device);
> > > + /*
> > > + * ACPI 6.5's 6.3.7 "_STA (Device Status)" allows firmware to return
> > > + * (!present && functional) for certain types of devices that should be
> > > + * enumerated. Note that the enabled bit should not be set unless the
> > > + * present bit is set.
> > > + *
> > > + * However, limit this only to processor devices to reduce possible
> > > + * regressions with firmware.
> > > + */
> > > + if (device->status.functional)
> > > + return true;
>
> I have a report from within Oracle that this causes testing failures
> with QEMU using -smp cpus=2,maxcpus=4. I think it needs to be:
>
> if (!device->status.present)
> return device->status.functional;
>
> if (device->status.enabled)
> return true;
>
> return !acpi_device_is_processor(device);
The above is fine by me.
> So we can better understand the history here, let's list it as a
> truth table. P=present, F=functional, E=enabled, Orig=how the code
> is in mainline, James=James' original proposal, Rafael=the proposed
> replacement but seems to be buggy, Rmk=the fixed version that passes
> tests:
>
> P F E Orig James Rafael Rmk
> 0 0 0 0 0 0 0
> 0 0 1 0 0 0 0
> 0 1 0 1 1 1 1
> 0 1 1 1 0 1 1
> 1 0 0 1 0 !processor !processor
> 1 0 1 1 1 1 1
> 1 1 0 1 0 1 !processor
> 1 1 1 1 1 1 1
>
> Any objections to this?
So AFAIAC it can return false if not enabled, but present and
functional. [Side note: I'm wondering what "functional" means then,
but whatever.]
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