To disable power saving on the card reader you need to write to the devices power/control file. To find the required file path you can check lsusb -tvv
your looking for the details of the 'media card controller`.
From the terminal…
loki@sikozu:~$ lsusb -tvv
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
ID 1d6b:0003 Linux Foundation 3.0 root hub
/sys/bus/usb/devices/usb2 /dev/bus/usb/002/001
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
ID 1d6b:0002 Linux Foundation 2.0 root hub
/sys/bus/usb/devices/usb1 /dev/bus/usb/001/001
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/3p, 480M
ID 0424:2640 Microchip Technology, Inc. (formerly SMSC) USB 2.0 Hub
/sys/bus/usb/devices/1-1 /dev/bus/usb/001/002
|__ Port 1: Dev 3, If 0, Class=Mass Storage, Driver=usb-storage, 480M
ID 0424:4041 Microchip Technology, Inc. (formerly SMSC) Hub and media card controller
/sys/bus/usb/devices/1-1.1 /dev/bus/usb/001/003
|__ Port 2: Dev 4, If 3, Class=Vendor Specific Class, Driver=option, 480M
ID 2020:2060
/sys/bus/usb/devices/1-1.2 /dev/bus/usb/001/004
|__ Port 2: Dev 4, If 1, Class=Vendor Specific Class, Driver=option, 480M
ID 2020:2060
/sys/bus/usb/devices/1-1.2 /dev/bus/usb/001/004
|__ Port 2: Dev 4, If 4, Class=Vendor Specific Class, Driver=qmi_wwan, 480M
ID 2020:2060
/sys/bus/usb/devices/1-1.2 /dev/bus/usb/001/004
|__ Port 2: Dev 4, If 2, Class=Vendor Specific Class, Driver=option, 480M
ID 2020:2060
/sys/bus/usb/devices/1-1.2 /dev/bus/usb/001/004
|__ Port 2: Dev 4, If 0, Class=Vendor Specific Class, Driver=option, 480M
ID 2020:2060
/sys/bus/usb/devices/1-1.2 /dev/bus/usb/001/004
From the above output you’ll see that the path for the Microchip Technology, Inc. (formerly SMSC) Hub and media card controller
is /sys/bus/usb/devices/1-1.1
You can check the current value (which should be “auto”) with…
cat /sys/bus/usb/devices/1-1.1/power/control
To disable power saving set the value to “on”…
sudo -i
echo on > /sys/bus/usb/devices/1-1.1/power/control
exit
This setting is not persistent and rebooting the phone will reset the option back to the default “auto”, echoing the default “auto” to the file will also revert the change.