linux-kernel - Re: [PATCH v2 2/4] power: reset: add reboot mode driver

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Date:	Tue, 19 Jan 2016 16:38:20 +0800
From:	Andy Yan <andy.yan@...k-chips.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	Heiko Stübner <heiko@...ech.de>,
	Arnd Bergmann <arnd@...db.de>, linux@...ck-us.net,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	geert+renesas@...der.be, sre@...nel.org,
	Olof Johansson <olof@...om.net>, dbaryshkov@...il.com,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	jun.nie@...aro.org,
	Paweł Moll <pawel.moll@....com>,
	f.fainelli@...il.com, Will Deacon <will.deacon@....com>,
	linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
	Linux PM list <linux-pm@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, lorenzo.pieralisi@....com,
	moritz.fischer@...us.com, cernekee@...il.com,
	lkml <linux-kernel@...r.kernel.org>, dwmw2@...radead.org,
	Mark Rutland <mark.rutland@....com>,
	maxime.ripard@...e-electrons.com,
	Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v2 2/4] power: reset: add reboot mode driver

Hi John:

On 2016年01月16日 04:27, John Stultz wrote:
> On Tue, Jan 12, 2016 at 3:31 AM, Andy Yan <andy.yan@...k-chips.com> wrote:
>> This driver parse the reboot commands like "reboot loader"
>> and "reboot recovery" to get a boot mode described in the
>> device tree , then call the write interfae to store the boot
>> mode in some persistent storage  like special register or ram,
>> which can be read by the bootloader after system reboot, then
>> the bootloader can take different action according to the mode
>> stored.
>>
>> This is commonly used on Android based devices, which in order
>> to reboot the device into fastboot or recovery mode.
>>
>> Signed-off-by: Andy Yan <andy.yan@...k-chips.com>
>
> Hey Andy!
>    Thanks for keeping this work going! I've just successfully reworked
> my Nexus7 tree to use your implementation (using the syscon version,
> setting up a syscon for IMEM as Bjorn had requested earlier).
>
> All is working well so far!
>
> The one thing I was working on supporting with my own version that
> seems to be missing here are for devices that use string based codes,
> rather then magic numbers.
>
> This was mostly a theoretical issue. I think the Galaxy Nexus used it,
> and when I was looking at some of the HTC devices, they support a text
> based reason along with the magic code, but at least in some
> implementations the text mode isn't used, so I suspect there its just
> for extra debugging.  So this may not be critical to solve until
> someone tries to add support for such a device.
>
> Anyway, I'm going to look at porting this to the HiKey board next
> (which just uses reserved ram, not syscon), so I'll try to do a an
> SRAM driver implementaiton to see how that goes.
>
> thanks!
> -john
>
>
>
>

  Very glad to hear news from you. And welcome your SRAM based driver 
implementation.