linux-kernel - Re: [PATCH 4/8] i2c: acpi: Use ACPI GPIO wake capability bit to set wake

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Date:   Thu, 8 Sep 2022 08:40:04 -0600
From:   Raul Rangel <rrangel@...omium.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     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>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        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

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).
>
> 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 ...
>
> Regards,
>
> Hans
>

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.