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

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Date:	Tue, 16 Jun 2015 11:39:26 +0200
From:	Noralf Trønnes <noralf@...nnes.org>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-watchdog@...r.kernel.org,
	linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] watchdog: bcm2835: Add poweroff code for the Raspberry
 Pi


Den 16.06.2015 05:07, skrev Stephen Warren:
> On 06/13/2015 05:39 AM, Noralf Trønnes 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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