Date:   Fri, 9 Sep 2022 12:47:11 -0600
From:   Raul Rangel <rrangel@...omium.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        linux-input <linux-input@...r.kernel.org>,
        "Limonciello, Mario" <mario.limonciello@....com>,
        Tim Van Patten <timvp@...gle.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wolfram Sang <wsa@...nel.org>,
        "open list:I2C SUBSYSTEM HOST DRIVERS" <linux-i2c@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/8] i2c: acpi: Use ACPI GPIO wake capability bit to set wake_irq

It looks like `i2c_acpi_get_irq` and `platform_get_irq_optional` are
doing pretty much the same thing. Can we replace `i2c_acpi_get_irq`
and switch over to `platform_get_irq_optional`? Is it possible to get
a `platform_device` from an `i2c_client`?

On Thu, Sep 8, 2022 at 9:23 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Thu, Sep 8, 2022 at 4:40 PM Raul Rangel <rrangel@...omium.org> wrote:
> >
> > On Wed, Sep 7, 2022 at 2:12 AM Hans de Goede <hdegoede@...hat.com> wrote:
> > >
> > > Hi,
> > >
> > > On 9/7/22 04:00, Raul Rangel wrote:
> > > > On Tue, Sep 6, 2022 at 7:00 PM Dmitry Torokhov
> > > > <dmitry.torokhov@...il.com> wrote:
> > > >>
> > > >> On Tue, Aug 30, 2022 at 05:15:37PM -0600, Raul E Rangel wrote:
> > > >>> Device tree already has a mechanism to pass the wake_irq. It does this
> > > >>> by looking for the wakeup-source property and setting the
> > > >>> I2C_CLIENT_WAKE flag. This CL adds the ACPI equivalent. It uses at the
> > > >>> ACPI GpioInt wake flag to determine if the interrupt can be used to wake
> > > >>> the system. Previously the i2c drivers had to make assumptions and
> > > >>> blindly enable the wake IRQ. This can cause spurious wake events. e.g.,
> > > >>> If there is a device with an Active Low interrupt and the device gets
> > > >>> powered off while suspending, the interrupt line will go low since it's
> > > >>> no longer powered and wake the system. For this reason we should respect
> > > >>> the board designers wishes and honor the wake bit defined on the
> > > >>> GpioInt.
> > > >>>
> > > >>> This change does not cover the ACPI Interrupt or IRQ resources.
> > > >>>
> > > >>> Signed-off-by: Raul E Rangel <rrangel@...omium.org>
> > > >>> ---
> > > >>>
> > > >>>  drivers/i2c/i2c-core-acpi.c |  8 ++++++--
> > > >>>  drivers/i2c/i2c-core-base.c | 17 +++++++++++------
> > > >>>  drivers/i2c/i2c-core.h      |  4 ++--
> > > >>>  3 files changed, 19 insertions(+), 10 deletions(-)
> > > >>>
> > > >>> diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c
> > > >>> index c762a879c4cc6b..cfe82a6ba3ef28 100644
> > > >>> --- a/drivers/i2c/i2c-core-acpi.c
> > > >>> +++ b/drivers/i2c/i2c-core-acpi.c
> > > >>> @@ -182,12 +182,13 @@ static int i2c_acpi_add_resource(struct acpi_resource *ares, void *data)
> > > >>>  /**
> > > >>>   * i2c_acpi_get_irq - get device IRQ number from ACPI
> > > >>>   * @client: Pointer to the I2C client device
> > > >>> + * @wake_capable: Set to 1 if the IRQ is wake capable
> > > >>>   *
> > > >>>   * Find the IRQ number used by a specific client device.
> > > >>>   *
> > > >>>   * Return: The IRQ number or an error code.
> > > >>>   */
> > > >>> -int i2c_acpi_get_irq(struct i2c_client *client)
> > > >>> +int i2c_acpi_get_irq(struct i2c_client *client, int *wake_capable)
> > > >>>  {
> > > >>>       struct acpi_device *adev = ACPI_COMPANION(&client->dev);
> > > >>>       struct list_head resource_list;
> > > >>> @@ -196,6 +197,9 @@ int i2c_acpi_get_irq(struct i2c_client *client)
> > > >>>
> > > >>>       INIT_LIST_HEAD(&resource_list);
> > > >>>
> > > >>> +     if (wake_capable)
> > > >>> +             *wake_capable = 0;
> > > >>> +
> > > >>>       ret = acpi_dev_get_resources(adev, &resource_list,
> > > >>>                                    i2c_acpi_add_resource, &irq);
> > > >>
> > > >
> > > >
> > > >> You also need to handle "Interrupt(..., ...AndWake)" case here. I would
> > > >> look into maybe defining
> > > >>
> > > >> #define IORESOURCE_IRQ_WAKECAPABLE      (1<<6)
> > > >>
> > > >> in include/linux/ioport.h and plumbing it through from ACPI layer.
> > > >>
> > > >> Thanks.
> > > >
> > > > AFAIK the Intel (Not 100% certain) and AMD IO-APIC's can't actually
> > > > wake a system from suspend/suspend-to-idle.
> > >
> > > That may be true for S3 suspend (it sounds about right) there
> > > certainly is no way to "arm for wakeup" on the APIC, but with
> > > s2idle all IRQs which are not explicitly disabled by the OS
> > > still function normally so there any IRQ can be a wakeup
> > > source (AFAIK).
>
> That's true.
>
> Moreover, even for S3 there are transitions into it and there may be
> wakeup interrupts taking place during those transitions.  Those may be
> any IRQs too.
>
> > > And even with S3 suspend I think some IRQs can act as wakeup,
> > > but that is configured by the BIOS then and not something which
> > > linux can enable/disable. E.g IIRC the parent IRQ of the GPIO
> > > controllers on x86 is an APIC IRQ ...
>
> It's more about how the system is wired up AFAICS.  Basically, in
> order to wake up the system from S3, the given IRQ needs to be
> physically attached to an input that will trigger the platform wakeup
> logic while in S3.
>
> > >
> >
> > SGTM. I wanted to make sure there was interest before I invested the
> > time in adding the functionality. Hopefully I can push up a new patch
> > set tomorrow.
>
> Sounds good. :-)

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