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

From: Noralf TrÃnnes
Date: Wed Jun 17 2015 - 06:59:03 EST

Den 17.06.2015 03:28, skrev Stephen Warren:
On 06/16/2015 03:39 AM, Noralf TrÃnnes wrote:
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.
We don't support those other board in mainline Linux AFAIK. In other
discussions, Eric Anholt stated that the Roku 2 for example doesn't use
the same firmware (albeit they were derived from the same base a long
way back apparently) so I have no good reason to believe this logic is a
standard across difference bcm2835 devices. Do you know more specific

I didn't know that only Raspberry Pi was supported and I have no details about
the other boards. I'll send a new patch. Thanks.

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