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Date:   Fri, 2 Sep 2022 22:06:54 -0700
From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
To:     Raul Rangel <rrangel@chromium.org>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        linux-input <linux-input@vger.kernel.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Mario Limonciello <mario.limonciello@amd.com>,
        Tim Van Patten <timvp@google.com>,
        "jingle.wu" <jingle.wu@emc.com.tw>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Tony Lindgren <tony@atomide.com>
Subject: Re: [PATCH 1/8] Input: elan_i2c - Use PM subsystem to manage wake irq
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On Wed, Aug 31, 2022 at 08:17:23PM -0600, Raul Rangel wrote:
> On Wed, Aug 31, 2022 at 1:16 PM Dmitry Torokhov
> <dmitry.torokhov@gmail.com> wrote:
> >
> > On Wed, Aug 31, 2022 at 12:12:41PM -0700, Dmitry Torokhov wrote:
> > > On Wed, Aug 31, 2022 at 08:01:12PM +0200, Rafael J. Wysocki wrote:
> > > > On Wed, Aug 31, 2022 at 1:16 AM Raul E Rangel <rrangel@chromium.org> wrote:
> > > > >
> > > > > The Elan I2C touchpad driver is currently manually managing the wake
> > > > > IRQ. This change removes the explicit enable_irq_wake/disable_irq_wake
> > > > > and instead relies on the PM subsystem. This is done by calling
> > > > > dev_pm_set_wake_irq.
> > > > >
> > > > > i2c_device_probe already calls dev_pm_set_wake_irq when using device
> > > > > tree, so it's only required when using ACPI. The net result is that this
> > > > > change should be a no-op. i2c_device_remove also already calls
> > > > > dev_pm_clear_wake_irq, so we don't need to do that in this driver.
> > > > >
> > > > > I tested this on an ACPI system where the touchpad doesn't have _PRW
> > > > > defined. I verified I can still wake the system and that the wake source
> > > > > was the touchpad IRQ GPIO.
> > > > >
> > > > > Signed-off-by: Raul E Rangel <rrangel@chromium.org>
> > > >
> > > > I like this a lot [...]
> > >
> 
> > > I also like this a lot, but this assumes that firmware has correct
> > > settings for the interrupt... Unfortunately it is not always the case
> > > and I see that at least Chrome OS devices, such as glados line (cave, chell, sentry,
> > > ect) do not mark interrupt as wakeup:
> > >
> > > src/mainboard/google/glados/variants/chell/overridetree.cb
> > >
> > >                         chip drivers/i2c/generic
> > >                                 register "hid" = ""ELAN0000""
> > >                                 register "desc" = ""ELAN Touchpad""
> > >                                 register "irq" = "ACPI_IRQ_LEVEL_LOW(GPP_B3_IRQ)"
> > >                                 register "wake" = "GPE0_DW0_05"
> > >                                 device i2c 15 on end
> > >
> 
> So the above entry specifies the `wake` register. This generates an
> ACPI _PRW resource. The patch series will actually fix devices like
> this. Today without this patch series we get two wake events for a
> device. The ACPI wake GPE specified by the _PRW resource, and the
> erroneous GPIO wake event. But you bring up a good point.

Does this mean that the example that we currently have in coreboot
documentation (Documentation/acpi/devicetree.md) is not correct:

device pci 15.0 on
        chip drivers/i2c/generic
                register "hid" = ""ELAN0000""
                register "desc" = ""ELAN Touchpad""
                register "irq" = "ACPI_IRQ_WAKE_LEVEL_LOW(GPP_A21_IRQ)"
                register "wake" = "GPE0_DW0_21"
                device i2c 15 on end
        end
end # I2C #0

Doesn't in say that we have both GpioIrq and GPE wakeup methods defined
for the same device?

> 
> I wrote a quick and dirty script (https://0paste.com/391849) to parse
> the coreboot device tree entries. Open source firmware is great isn't
> it? ;)
> 
> $ find src/mainboard/google/ -iname '*.cb' | xargs awk -f touch.awk --
> src/mainboard/google/eve/devicetree.cb

...

> src/mainboard/google/sarien/variants/sarien/devicetree.cb
> 1
> chip drivers/i2c/generic
> register "hid" = ""ELAN0000""
> register "desc" = ""ELAN Touchpad""
> register "irq" = "ACPI_IRQ_EDGE_LOW(GPP_B3_IRQ)"
> register "probed" = "1"
> device i2c 2c on end
> end
> Total Touchpad: 202
> Total Wake: 195
> 
> Out of all the touchpads defined on ChromeOS it looks like only 4
> devices are missing a wake declaration. I omitted touchpanels because
> ChromeOS doesn't use those as a wake source. chromeos_laptop.c already
> defines some devices with i2c board_info and it sets the
> `I2C_CLIENT_WAKE` flag. I'm not sure if this is actually working as
> expected. `i2c_device_probe` requires a `wakeup` irq to be present in
> the device tree if the `I2C_CLIENT_WAKE` flag is set, but I'm assuming

No it does not. If there is no wakeup IRQ defined of_irq_get_byname()
will return an error and we'll take the "else if (client->irq > 0)"
branch and will set up client->irq as the wakeup irq.

> the device tree was missing wake attributes.

> 
> Anyway, patches 6, and 7 are the ones that drop the legacy behavior. I
> can figure out how to add the above boards to chromeos_laptop.c and
> get the wake attribute plumbed, or I can add something directly to the
> elan_i2c_core, etc so others can add overrides for their boards there.
> I'll also send out CLs to fix the device tree configs (not that we
> would run a FW qual just for this change).

My preference is to limit board-specific hacks in drivers if we can, so
adding missing properties to chromeos_laptop.c would be my preference.

Thanks.

-- 
Dmitry