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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Fri, 5 Aug 2022 19:08:05 +0200
Message-ID: <CAJZ5v0ie7B=GvhbfBsi7Zxu+=YzYKUqvUNs6dNZQfT3CRm=KPg@mail.gmail.com>
Subject: Re: [PATCH] i2c: ACPI: Do not check ACPI_FADT_LOW_POWER_S0
To:     "Limonciello, Mario" <mario.limonciello@amd.com>
Cc:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Jiri Kosina <jikos@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux ACPI <linux-acpi@vger.kernel.org>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        linux-input <linux-input@vger.kernel.org>,
        "rrangel@chromium.org" <rrangel@chromium.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Kai-Heng Feng <kai.heng.feng@canonical.com>
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On Fri, Aug 5, 2022 at 6:59 PM Limonciello, Mario
<mario.limonciello@amd.com> wrote:
>
> On 8/5/2022 11:51, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > The ACPI_FADT_LOW_POWER_S0 flag merely means that it is better to
> > use low-power S0 idle on the given platform than S3 (provided that
> > the latter is supported) and it doesn't preclude using either of
> > them (which of them will be used depends on the choices made by user
> > space).
> >
> > Because of that, ACPI_FADT_LOW_POWER_S0 is generally not sufficient
> > for making decisions in device drivers and so i2c_hid_acpi_probe()
> > should not use it.
> >
> > Moreover, Linux always supports suspend-to-idle, so if a given
> > device can wake up the system from suspend-to-idle, then it can be
> > marked as wakeup capable unconditionally, so make that happen in
> > i2c_hid_acpi_probe().
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> +Raul
> +Hans
> +KH
>
> Raul had a patch that was actually going to just tear out this code
> entirely:
> https://lkml.kernel.org/lkml/20211220163823.1.Ie20ca47a26d3ea68124d8197b67bb1344c67f650@changeid/
>
> As part of that patch series discussion another suggestion had
> transpired
> (https://patchwork.kernel.org/project/linux-input/patch/20211220163823.2.Id022caf53d01112188308520915798f08a33cd3e@changeid/#24681016):
>
> ```
> if ((acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0) &&
>             !adev->flags.power_manageable) {
>                  device_set_wakeup_capable(dev, true);
>                  device_set_wakeup_enable(dev, false);
>          }
> ```
>
> If this is being changed, maybe consider that suggestion to
> check `adev->flags.power_manageable`.

Fair enough, I'll send a v2 with this check added.