Disable power management on Raspberry Pi USB Wifi interface

gistfile1.md

Too early to tell whther this solved my problem but recording for posterity anyway. In theory this will stop my Raspberry Pi from dropping off the network after it has been idle for a while.

Before

pi@dashboard ~ $ iwconfig
wlan0     IEEE 802.11bgn  ESSID:"Professor Ping"
     Mode:Managed  Frequency:2.437 GHz  Access Point: B8:E6:25:9B:62:02
     Bit Rate=39 Mb/s   Tx-Power=20 dBm
     Retry  long limit:7   RTS thr:off   Fragment thr:off
     Power Management:on
     Link Quality=43/70  Signal level=-67 dBm
     Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
     Tx excessive retries:70  Invalid misc:14   Missed beacon:0

lo        no wireless extensions.

eth0      no wireless extensions.

Note: Power Management:on

Then

sudo nano  /etc/network/interfaces

add line: wireless-power off

After

pi@dashboard ~ $ iwconfig
wlan0     IEEE 802.11bgn  ESSID:"Professor Ping"
          Mode:Managed  Frequency:2.437 GHz  Access Point: B8:E6:25:9B:62:02
          Bit Rate=26 Mb/s   Tx-Power=20 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=43/70  Signal level=-67 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:29  Invalid misc:8   Missed beacon:0

lo        no wireless extensions.

eth0      no wireless extensions.

Note: Power Management:off

gistfile2.md

OK, new theory: pm-utils is disabling the interface.

Based on pm-utils info on ArchWiki I found a hook invoking wpa_supplicant to disable the wifi interface:

$ cat /usr/lib/pm-utils/sleep.d/60_wpa_supplicant

#!/bin/sh

# /etc/pm/sleep.d/60_wpa_supplicant
# Action script to notify wpa_supplicant of pm-action events.

PATH=/sbin:/usr/sbin:/bin:/usr/bin

WPACLI=wpa_cli

case "$1" in
    suspend|hibernate)
        $WPACLI suspend
        ;;
    resume|thaw)
        $WPACLI resume
        ;;
esac

exit 0

To disable that hook I created a dummy hook in 1/etc/pm/sleep.d/`:

sudo touch /etc/pm/sleep.d/60_wpa_supplicant
sudo chmod 644 /etc/pm/sleep.d/60_wpa_supplicant # Instructions said no exec flag

I rebooted for good measure. We'll see whether this one takes.

I'm also interested...

Did this work? Trying to ensure USB power management is disabled on a Raspberry Pi, but typical Debian Jessie install on Raspberry Pi, does not have pm-utils installed, does not have a /etc/pm directory tree at all.

Thank you so much! For me the solution in gistfile2.md works (on RPi 4, Raspbian buster) and the WiFi finally works properly.