0

After installing Arch Linux ARM on Raspberry Pi 3 model B, everything is working as expected but the green LED that indicates the SD card read write activity. The LED just blinks every second for 0.1 seconds and continues.

After installation, I did change the kernel printk otherwise it would show thousands of messages in any tty which is bad while installation. The /etc/sysctl.d/20-quiet-printk.conf goes as follows:

kernel.printk = 7 4 1 7

cat /sys/class/leds/led0/trigger produces the following output:

none rfkill-any rfkill-none kbd-scrolllock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock kbd-ctrlllock kbd-ctrlrlock usb-gadget usb-host timer oneshot heartbeat backlight gpio cpu cpu0 cpu1 cpu2 cpu3 activity default-on transient flash torch input panic netdev mmc1 [mmc0] rfkill0

How can I fix the LED blinking issue?

  • What does cat /sys/class/leds/led0/trigger output? How about grep "dtparam=act_led*" /boot/config.txt? – Roger Jones Feb 28 at 19:43
  • It gives the following output: none rfkill-any rfkill-none kbd-scrolllock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock kbd-ctrlllock kbd-ctrlrlock usb-gadget usb-host timer oneshot heartbeat backlight gpio cpu cpu0 cpu1 cpu2 cpu3 activity default-on transient flash torch input panic netdev mmc1 [mmc0] rfkill0 – Sourav Goswami Feb 28 at 19:44
  • 1
    OK, so the LED is setup to trigger on mmc0 (indicated by the square brackets) so should be indicating SD card activity. As a test try echo heartbeat | sudo tee /sys/class/leds/led0/trigger, should change to a double-flash "heartbeat" pattern. – Roger Jones Feb 28 at 19:49
  • But it doesn't work with SD cards. BTW, I am now using USB to boot for the time being. Is there a way I can add the /dev/sda2 to there? – Sourav Goswami Feb 28 at 19:51
  • 1
    The LED controller is obviously working so I've no idea why mmc0 would not be working as you expect or how you'd go about getting it to show activity for other disks. I think you can create your own LED status triggers but they live in the kernel so might be too much of a stretch and is beyond the original question. Documentation on the available triggers is a little sparse as well so choosing one based on the name is sometimes pot-luck! github.com/torvalds/linux/blob/master/Documentation/leds/… github.com/raspberrypi/linux/tree/rpi-4.19.y/drivers/leds/… – Roger Jones Feb 28 at 21:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.