How to disable superfluous Raspberry Pi interfaces?

[RasbPi]

How to disable superfluous Raspberry Pi interfaces in Raspbian?
For work me need only ethernet port and one USB port.
Give step-by-step instruction as it to make.

Whether it is possible to establish the USB 1.1 mode for USB ports?

[jamesh]

What do you mean by disable? Remove the drivers from the Linux kernel, or just ensure that they are not using any CPU? Because if the later, if you are not using them, they shouldn't be affecting the performance at all.

[RasbPi]

Ideal - power off the module
My purpose, heating and power consuming lowering.
First of all it belongs to USB and the LAN9512 chip.

[RaTTuS]

wait for a model A and then use that
the ethernet is connected via the usb port so you need both
the power used by said units is so small as not to be an issue in any office environment

[Grumpy Mike]

First of all it belongs to USB and the LAN9512 chip.

The same chip handles 2 USB connections so you can't only have one and shut the other down.
Anyway the Pi board was not designed to power down individual chips anyway, to do so is a) harder than you might think and then b) adds cost to the Pi.

[mikerr]

It is possible to power down the USB&ethernet chip (saving about 0.5W)
- but that leaves you without any USB or ethernet, so a little pointless.

While the Pi is quite low power on its own - it wasn't primarily built with power saving in mind
- the voltage regulator for instance is not as efficient as it might be, some have replaced that with a better one saving 30%
http://www.raspberrypi.org/phpBB3/viewt ... 63&t=12387

Also there's an optional software patch to reduce the hit of interrupts to service USB to gain a further 10% (while idle):
http://www.raspberrypi.org/phpBB3/viewt ... 6&start=75

[malex984]

It is possible to power down the USB&ethernet chip (saving about 0.5W)
- but that leaves you without any USB or ethernet, so a little pointless.

One can use UART for communication with RPi instead.
Besides, that SMSC usb/ethernet chip is responsible is heating even if unused.

So, how do you power down it?

[mikerr]

Code: Select all

echo 1 > /sys/devices/platform/bcm2708_usb/bussuspend

Unfortunately its then off until reboot ... (not sure if someone has a fix ?)

[rew]

Besides, that SMSC usb/ethernet chip is responsible is heating even if unused.

The lan9512 chip uses a lot less current if you leave it powered down. This can be seen by monitoring the power-use of the raspberry pi during boot. The current shoots up significantly when the '9512 wakes up.

[mikerr]

Mind you if you're powering the ethernet/usb hub down all the time, might as well get a Model A for even lower consumption

[jojopi]

bussuspend does not power down the 9512, although it does save 150mA, which is a lot.

I expected that holding the chip in reset via GPIO6 would be better, but actually the only difference is that that shuts down the ethernet PHY as well. (Which saves another 50mA or so, but only if you actually have an ethernet cable connected.)

The lowest current I could get on an idle Model B with USB/LAN disabled was 200mA, whereas people report the Model A idles at 110mA.

I tested both revisions, because I thought perhaps that IC3 core could be remaining powered via RG1 on a Rev1, but there was no difference.

Incidentally, I did manage to restore USB/LAN without reboot by putting the 9512 in reset during the un-bussuspend, and then ifdown/ifup eth0 afterwards. Not sure if this is reliable though. It is certainly potentially sequence-sensitive; I saw at least one kernel oops testing GPIO6 on its own.