[Gta04-owner] Modem USB suspend (possible ~80mA reduction on active system?)

Sebastian Krzyszkowiak dos at dosowisko.net
Sun Jun 1 22:27:37 CEST 2014


On Sun, Jun 1, 2014 at 10:09 AM, Dr. H. Nikolaus Schaller
<hns at goldelico.com> wrote:
>> I have added following udev rule:
>> ACTION=="add", SUBSYSTEMS=="*", TEST=="power/control",
>> ATTR{power/control}="auto"
> isn't that a little too generic?

Right, it was just a quick test. Proper "production-ready" rule would
be limited either to the modem or to USB devices (I guess suspend
could be beneficial also for devices connected to OTG, although it
most likely depends on specific use case).

>> ...and power saving mode is now enabled automatically on boot.
>> Is this something that was already known or a new finding? (it's for
>> sure something new for SHR it seems ;))
> I don't remember that we did discuss that before. Maybe it was done
> in QtMoko because Radek just was more aware, but he can comment
> best on this.
> At least it should reduce power consumption while the device is
> resumed. It will not save power during suspend (which is the more
> critical part because id defines the standby time).

Sure, but with WiFi (or 3G data connection, although this finding
won't help much there) enabled the device becomes a massive power hog,
eating more than 500mA from the battery, making it hot and discharged
in very short time. I noticed that sometimes on both SHR and
Replicant, so reducing power consumption while the device is not in
suspend is IMHO very important as well.

> There is also a minor difference between GTM601 and PHS8. The
> PHS8 has a sense line to detect the +5V VBUS while the GTM601
> doesn't (it just looks for 3.3V activity on D+ and D-).
> So the way VBUS of a real or "virtual" USB host socket is controlled
> by the EHCI+PHY subsystem may also influence the modem going
> to sleep.
> BR,
> Nikolaus
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Sebastian Krzyszkowiak, dos

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