Public bug reported:
Impact:
People are reporting that the green led (the one next to the red power
led) is not working on the RaspberryPi 3B+ board.
After debugging the issue, this is what i found:
1) in reality, it's not the green led that is not working, but is the
power led that "fails":
...
[ 2.299216] leds-gpio: probe of soc:leds failed with error -2
...
what happens is that, since all leds are initialized in a loop, if one
of them fail to init properly, the loop tears down all the initialized
leds in that loop - one can easily proof that by adding debug to
drivers/leds/leds-gpio.c::gpio_leds_create() and drivers/leds/leds-
gpio.c::gpio_led_probe(), or simply commenting out the pwr_led block in
arch/arm/boot/dts/bcm2710-rpi-3-b-plus.dts - the board will boot up, the
above leds-gpio error will disappear and act_led will work properly.
2) the pwr_led in all rpi3 boards (rpi3 a/b classic or b+) are not
available direcly by the OS, instead only the Bradcom firmware can
manipulate its gpio, thus a new mechanism that used the bcm firmware as
a middleman was developed - the exgpio driver: using a mailbox
mechanism, messages are sent from the Linux kernel to the Broadcom
firmware to query the status of the led GPIO or set it, this was it's
possible for the linux led trigger to make it work.
Fix:
The original
Regression:
** Affects: linux-raspi2 (Ubuntu)
Importance: Undecided
Status: Invalid
** Changed in: linux-raspi2 (Ubuntu)
Status: New => Invalid
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https://bugs.launchpad.net/bugs/1808366
Title:
Led trigger not working on rpi3b+
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