Re: [PATCH v2 2/3] watchdog: bcm2835: Add poweroff code for the Raspberry Pi

From: Noralf TrÃnnes
Date: Tue Jun 16 2015 - 05:39:49 EST

Den 16.06.2015 05:07, skrev Stephen Warren:
On 06/13/2015 05:39 AM, Noralf TrÃnnes wrote:
This adds a new poweroff function to the watchdog driver for the
Raspberry Pi. Currently poweroff/halt results in a reboot.

The Raspberry Pi firmware uses the RSTS register to know which
partiton to boot from. The partiton value is spread into bits
0, 2, 4, 6, 8, 10. Partiton 63 is a special partition used by
the firmware to indicate halt.

The firmware made this change in 19 Aug 2013 and was matched
by the downstream commit:
Changes for new NOOBS multi partition booting from gsh
I don't understand why we need a new compatible value here; why not
simply modify the existing bcm2835_power_off() function. That is written
to do something that's interpreted by the RPi firmware, not something
that the bcm2835 HW does.

Admittedly the current name is a bit misleading, but fixing that should
be a separate change to fixing the implementation to do what the current
firmware expects.

There are other boards that use the BCM2835 and I didn't want to break the
behaviour for those that use the reference firmware. Roku 2 device uses
this soc, and changing bcm2835_power_off() would break support for it.
ODROID-W also use BCM2835, but this is a Pi clone so I don't know if they
have matched their firmware behaviour to that of the Pi (admittedly not
many boards were made, their source of chips went dry).

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