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Date:   Tue, 6 Sep 2022 11:40:50 -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 Tue, Sep 06, 2022 at 11:18:49AM -0600, Raul Rangel wrote:
> On Fri, Sep 2, 2022 at 11:07 PM Dmitry Torokhov
> <dmitry.torokhov@gmail.com> wrote:
> >
> > 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?
> 
> Hrmm, yeah that is wrong and will cause duplicate wake events for the
> device. I'll push a CL to clean up the documentation.

Thanks. I think we also need to clean up our ADL boards (and likely
more).

> 
> >
> > >
> > > 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.
> 
> Oh thanks for pointing that out. I might refactor patch #4 to just set
> the `I2C_CLIENT_WAKE` flag when `acpi_wake_capable` is true.
> 
> >
> > >
> > > 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.
> 
> How should we handle non chromeos boards?

My preference would be to shove something like chromeos_laptop into
drivers/platform/x86... Something like
drivers/platform/x86/x86-android-tablets.c

Thanks.

-- 
Dmitry