power management

From SMSC's datasheet on the LAN9512 @ http://www.smsc.com/media/Downloads_Public/Data_Sheets/9512.pdf  :-

— Implements Reduced Power Operating Modes

— Advanced power saving features

— Downstream PHY goes into low power mode when port power to the port is disabled

— Full Power Management with individual or ganged power control of each downstream port.

 

1.1.6 Power Management

The LAN9512/LAN9512i features three variations of USB suspend: SUSPEND0, SUSPEND1, and SUSPEND2. These modes allow the application to select the ideal balance of remote wakeup functionality and power consumption.

 

   SUSPEND0: Supports GPIO, “Wake On LAN”, and “Magic Packet” remote wakeup events. This suspend state reduces power by stopping the clocks of the MAC and other internal modules.

   SUSPEND1: Supports GPIO and “Link Status Change” for remote wakeup events. This suspend state consumes less power than SUSPEND0.

   SUSPEND2: Supports only GPIO assertion for a remote wakeup event. This is the default suspend mode for the LAN9512/LAN9512i.

 

4.3.1 SUSPEND0

    Power Dissipation (Device and Ethernet components) 379 mW

4.3.2 SUSPEND1

    Power Dissipation (Device and Ethernet components) 229 mW

4.3.2 SUSPEND2

    Power Dissipation (Device and Ethernet components) 14.1 mW

So, it seems that you'll be in luck once we figure out how to activate the power-down modes, which presumably is done in the driver but might already have control points brought out into /sys space.

I'm puzzled why there is so much variation in the temperature that people are seeing under zero traffic conditions though.  It's a long shot, but I guess it's worth checking that the 3.3V really is 3.3V.  Assuming that the supply is in spec, then this does rather look like SMSC's manufacturing parameter control is rather poor.

While I'm at it, the maximum specified operational power seems to be:

4.3.4 Operational Current Consumption & Power Dissipation

100BASE-TX Full Duplex (USB High-Speed)

     Supply current (VDD33IO, VDD33A) 231 mA

     Power Dissipation (Device Only) 763 mW

PS. Great idea to power it from the USB-UART for headless operation!

Morgaine.

jbeale,

   very impressive.

You can disable the usb by doing (as root)

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

which stops the 8000 interrupts/sec, and probably will save power.

You can also desolder the lan chip, as at least one user has done.

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=6747&start=153

Good catch, coder27.  Dom seems to have posted that info:  http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=7866#p95086

I wonder which of the three LAN9512 suspend modes it activates.  Hopefully SUSPEND2, if there is only a single boolean control.

I also posted this at http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=7866&sid=29a2c3f1cba25fb9122f3f047afbbb92&start=25#p111978

In case of interest: with the R-Pi sitting idle with 'top' load average: 0.00, 0.01, 0.05

No monitor, no video, no USB and no Ethernet devices connected (UART serial port only -see http://www.raspberrypi.org/phpBB3/viewtopic.php?f=44&t=9665).

Voltage is measured onboard, TP1-TP2.  Ambient surface temperature is 27 C, air temp 24 C.

IR thermometer: MicroTemp MT100 cross-checked with thermocouple sensor.

RPi power draw:  318 mA at 5.0 V (1.59 W)   Chip temperatures: SoC: 46 C, Eth/USB: 51 C, SD card: 32 C

after this command as root, and waiting 10 minutes for temperature to stabilize

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

RPi power draw: 182 mA at 5.0 V (0.91 W)  Chip temperatures: SoC: 40 C, Eth/USB: 39 C, SD card: 30 C

so the system uses 1.59 W when idle but Eth/USB on, and 0.91 W when Eth/USB shut down, nearly half the power. This could make a difference in some possible use cases, where you want to power up the high-bandwidth link only when needed. I wonder if the Eth/USB system be turned back on after "bussuspend" without doing a full reboot- hopefully so.

echo 0 > /sys/devices/platform/bcm2708_usb/bussuspend

will almost certainly turn it back on.  That's how all the other controls in /sys work.

I should be able to check myself next week.   \o/

Morgaine.

That was the first thing I tried, but assumed it did not work, because the current draw remained at 182 mA, and also I could not mount a USB device. I think something else has to be manually restarted.

Ah.  Well the values of leaf entries in /sys don't have to be boolean, so they might have mapped the suspend values as

0 - SUSPEND0 - 379 mW

1 - SUSPEND1 - 229 mW

2 - SUSPEND2 - 14 mW

3 - No suspend - 763 mW, everything on, default value of bussuspend

or indeed any other numeric mapping.  So it's worth trying all the low numbers.

I could try to figure it out from the driver, but it's really dark in there and I got scared the last time I looked. :-P

PS. Try reading the value first after a reboot, to determine its default value.  (cat .../bussuspend)

Morgaine.

jbeale wrote:

 

I think something else has to be manually restarted.

Are there any other control entries in the same directory as "bussuspend", something related to "wakeup" perhaps, or "resume"?

Immediately after a fresh boot:

pi@raspberrypi:~$ cat /sys/devices/platform/bcm2708_usb/bussuspend

Bus Suspend = 0x0

pi@raspberrypi:~$ cat /sys/devices/platform/bcm2708_usb/buspower

Bus Power = 0x1

pi@raspberrypi:~$ cat /sys/devices/platform/bcm2708_usb/busconnected

Bus Connected = 0x1

and after the suspend action, Bus Power and Bus Connected go to 0. But even root can't write to ~/busconnected, maybe it's a read-only status bit?

root@raspberrypi:/home/pi# echo 0 > /sys/devices/platform/bcm2708_usb/bussuspend

root@raspberrypi:/home/pi# echo 1 > /sys/devices/platform/bcm2708_usb/buspower

root@raspberrypi:/home/pi# echo 1 > /sys/devices/platform/bcm2708_usb/busconnected

bash: /sys/devices/platform/bcm2708_usb/busconnected: Permission denied

root@raspberrypi:/home/pi# cat /sys/devices/platform/bcm2708_usb/busconnected

Bus Connected = 0x0

There are other devices, but I think I need some more info...

pi@raspberrypi:~$ ls /sys/devices/platform/bcm2708_usb/

busconnected  ggpio      gusbcfg     hsic_connect  regdump        subsystem

buspower      gnptxfsiz  hcddump     inv_sel_hsic  regoffset      uevent

bussuspend    gotgctl    hcd_frrem   modalias      regvalue       usb1

devspeed      gpvndctl   hnp         mode          remote_wakeup  wr_reg_test

driver        grxfsiz    hnpcapable  pools         spramdump

enumspeed     gsnpsid    hprt0       power         srp

gadget        guid       hptxfsiz    rd_reg_test   srpcapable