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Subject: Re: udev USB autosupend whitelist (was Re: [PATCH] Bluetooth: btusb:
 Restore QCA Rome suspend/resume fix with a "rewritten" version)
To:     Brian Norris <briannorris@chromium.org>
Cc:     Marcel Holtmann <marcel@holtmann.org>,
        Gustavo Padovan <gustavo@padovan.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        linux-bluetooth@vger.kernel.org, linux-serial@vger.kernel.org,
        linux-acpi@vger.kernel.org, stable@vger.kernel.org,
        Leif Liddy <leif.linux@gmail.com>,
        Matthias Kaehlcke <mka@chromium.org>,
        Daniel Drake <drake@endlessm.com>,
        Kai-Heng Feng <kai.heng.feng@canonical.com>,
        matadeen@qti.qualcomm.com, linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Benson Leung <bleung@chromium.org>
References: <20180108094416.4789-1-hdegoede@redhat.com>
 <20180213022455.GA151190@rodete-desktop-imager.corp.google.com>
 <8cd918fd-bf6f-70ac-e561-e7deffa695f0@redhat.com>
 <20180216022721.GA69988@rodete-desktop-imager.corp.google.com>
 <0a13d0f3-8e0d-74df-df9c-2bf0622a9fb6@redhat.com>
 <20180216164924.GA72213@rodete-desktop-imager.corp.google.com>
From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <28da6a0a-cda6-82f1-9200-4a0bb30c0663@redhat.com>
Date:   Mon, 19 Feb 2018 15:59:42 +0100
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Hi,

On 16-02-18 17:49, Brian Norris wrote:
> + Benson (and there are probably others that know better answers)
> 
> Hi,
> 
> On Fri, Feb 16, 2018 at 09:26:37AM +0100, Hans de Goede wrote:
>> Going a bit off-topic here, so changed the subject.
>> I will reply on topic in another mail.
>>
>> On 16-02-18 03:27, Brian Norris wrote:
>>> I use a set of udev rules that manually whitelist devices for
>>> autosuspend. You can see it here:
>>>
>>> https://chromium.googlesource.com/chromiumos/platform2/+/43728a93f6de137006c6b92fbb2a7cc4f353c9bf/power_manager/udev/gen_autosuspend_rules.py#83
>>>
>>> You'll find at least one Rome chip in there.
>>
>> Oh, that is a very interesting link for the work I've been doing to
>> improve Linux power-consumption in general:
>>
>> https://fedoraproject.org/wiki/Changes/ImprovedLaptopBatteryLife
>>
>> I was actually planning on at least doing such a list for WWAN modems,
>> for btusb my approach has been to just enable it everywhere
>> (except for QCA devices as I got bugreports for those).
>>
>> Note that I plan to eventually submit this whitelist to the
>> udev rules which are part of systemd upstream, so if chromeos
>> is using systemd too, this is something to be aware of for you.
> 
> Chrome OS does not currently use systemd, but thanks for the heads up.
> 
>> Question, is the white-listing of the root and rate-limiting
>> hubs really necessary? I thought these have this enabled by default?
> 
> This list is old and maintained by several of my team, originating from
> quite a ways back (i.e., much older kernels). It's quite possible that
> some of it is redundant today.

Ok, I double checked and it seems that explicitly setting power/control
to auto for any USB hub is not necessary as they all default to auto
now.

So FWIW you may want to consider removing this.

Regards,

Hans