does the BBGW wifi hardware have a power saving mode?

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1

Does the BBGW or the wifi hardware on the BBGW have some sort of power saving mode?

Something interesting I noticed about those “wlcore: ERROR SW watchdog interrupt received! starting recovery” messages that fill up my serial console: I get one almost every time the BBGW sends out a packet. This corresponds to my ~95% packet loss.

But if I run this command on my BBGW to frequently ping the wifi router, I never see the error message, and wifi networking works correctly:

sudo ping -i 0.1 192.168.1.1

If I increase the length of time to 0.2 seconds or longer, then the problem happens and I lose wifi connectivity. But as long as there is a steady stream of packets every 0.1 seconds or shorter, wifi works perfectly. Which is why I was wondering – could the wifi hardware be trying to go into some sort of power saving mode?

$ uname -a
Linux beaglebone 4.4.27-ti-r63 #1 SMP Thu Nov 3 19:58:15 UTC 2016 armv7l GNU/Linux

Stéphane

2

Hi Stephane,
Yes WL18xx does have a power save mode which is on by default. It can be disabled with

echo 0 > /sys/kernel/debug/ieee80211/phy0/wlcore/sleep_auth

The SW interrupt message means that the linux driver did not get a response from the WL18xx firmware within a defined time and so represents the fact that WL18xx has gone off into the weeds. It is often related to power management changes in the MMC driver.

Iain

3

Yes WL18xx does have a power save mode which is on by default. It can be disabled with
echo 0 > /sys/kernel/debug/ieee80211/phy0/wlcore/sleep_auth

That seems to have made a difference, Iain. My BBGW doesn’t do it every time, so I cannot yet say for certain, but so far today the 2 times the BBGW boots up with those error messages and a non-working wlan0, I login through the serial console interface, run that command, and everything then starts working again.

The default value for /sys/kernel/debug/ieee80211/phy0/wlcore/sleep_auth seems to be 2. I eventually found WL1271_PSM_ELP = 2 (power saving move, extreme low power) in acx.h. If anyone else is curious, the possible values 0, 1, and 2 are defined as:

/* Active mode */

WL1271_PSM_CAM = 0,

/* Power save mode */
WL1271_PSM_PS = 1,

/* Extreme low power */
WL1271_PSM_ELP = 2

Stéphane