-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Somebody in the thread at some point said:
|> But there is an argument that sticking LEDs on in suspend is not good, |> it can violate user expectation about battery life while in suspend (ie, |> halve it). And currently entry to suspend is a user action, he can |> notice LED lit at that time; again currently by definition the |> notificaton cannot be started to be displayed during the time the CPU is |> suspended either... but it can be shown quickly on wake when the user is |> definitely attending to it. |> | In my application, suspend is not a user action. It occurs when there is | no event within a specified period of time. Just like any modern screen Well I wholeheartedly approve of this stern powersaving attitude, it's clearly the way. | saver. I didn't realize that LEDs were so power hungry. But I would like It's not that the LEDs are so bad but that the suspend current with GSM up is pretty low already, IIRC 7 - 10mA @ VB average. LEDs eat 5 - 20mA @ ~2V depending on the type. And because of the logic above, an LED is going to either be off the whole duration of suspend or on the whole duration. | to essentially prevent them from suspending when I am plugged into I guess the way for this would be to extend the led class to expose a /sys attribute per LED that lets you defeat suspend turnoff (defaulting to current situation) and take care of setting it in userspace. I don't mind carrying it as a local patch, as upstream may or may not treat the idea kindly. | power. How about the timers that they are connected to for a timed | trigger? I'd assume it is an on or off deal when in suspend and no | blinking. Yes, in suspend the CPU core is literally unpowered and the PLLs are down; the GPIO registers are held just as dumb registers. All the peripherals are unclocked or unpowered... in this way we get the very best power behaviour. Vast bulk of that 7 - 10mA is going in the GSM section because that's up, our suspend current with GSM off was in 1 - 2mA range. - -Andy -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iEYEARECAAYFAkhPjA8ACgkQOjLpvpq7dMpKZwCeNynr/tSvgq/xl/mFy7Zwy5Ch t0MAn2lwNUjoxKY/OW0aEtywRy9DXs/f =QUZl -----END PGP SIGNATURE-----
