During halt powerdown, what code blinks the led ten times?

[MartyMacGyver]

During a system halt (power down) what code actually blinks the act LED 10 times?

I've been perusing the code and what appears to happen during the processing of the halt command, but I don't see where the activity LED (led0) is blinked ten times before the actual halt (and it's part of halt itself - "halt -d -f -p" will indeed immediately halt the system with the ten blinks). Anyone happen to know the kernel/CPU code enough to say?

Note that I've been poring over the code in https://github.com/raspberrypi/linux but I'm not finding it there. It's been suggested it might be in the GPU blob but I'm not sure of that either.

Is there a good architectural description of a Pi's instance lifecycle, from power on to halt/power off? When the "blob" hands over to the kernel and when or if it resumes control before the halt?

[DougieLawson]

It's the GPU code shutting down. As soon as the ten winks are done you can safely pull the power.

[MartyMacGyver]

Interesting! I thought perhaps the GPU only mediated bootup.

Do you happen to know at what point in the kernel code the Pi hands over to the GPU for the final part of the shutdown? Is it "pm_power_off()"?

[mimi123]

Interesting! I thought perhaps the GPU only mediated bootup.

Do you happen to know at what point in the kernel code the Pi hands over to the GPU for the final part of the shutdown? Is it "pm_power_off()"?

The GPU has always full control...
The ten times blink routine is apparently in bootcode.bin.
I had some fun using the arm_stop(),arm_halt() then arm_setup(),arm_start() videocore routines.

[MartyMacGyver]

The GPU has always full control...
The ten times blink routine is apparently in bootcode.bin.
I had some fun using the arm_stop(),arm_halt() then arm_setup(),arm_start() videocore routines.

Still getting my head wrapped around the GPU being superior to the CU in the hierarchy.

How did you manage to find those routines anyway? (I notice some are buried in the elf binaries...)

[mimi123]

The GPU has always full control...
The ten times blink routine is apparently in bootcode.bin.
I had some fun using the arm_stop(),arm_halt() then arm_setup(),arm_start() videocore routines.

Still getting my head wrapped around the GPU being superior to the CU in the hierarchy.

How did you manage to find those routines anyway? (I notice some are buried in the elf binaries...)

I have a unstripped blob.
commit affe5cd9d3e1e8dcc29509f12fc3ed5153f3fb67 in raspberrypi/firmware