linux-kernel - Re: [PATCH v1 0/6] misc: add reboot mode driver

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Message-ID: <20151222164742.GA8623@piout.net>
Date:	Tue, 22 Dec 2015 17:47:42 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Andy Yan <andy.yan@...k-chips.com>
Cc:	robh+dt@...nel.org, heiko@...ech.de, arnd@...db.de,
	john.stultz@...aro.org, sjg@...omium.org, treding@...dia.com,
	galak@...eaurora.org, ijc+devicetree@...lion.org.uk,
	wxt@...k-chips.com, catalin.marinas@....com, olof@...om.net,
	geert+renesas@...der.be, linux-rockchip@...ts.infradead.org,
	dbaryshkov@...il.com, sre@...nel.org, jun.nie@...aro.org,
	pawel.moll@....com, will.deacon@....com, akpm@...ux-foundation.org,
	devicetree@...r.kernel.org, linux@....linux.org.uk,
	gregkh@...uxfoundation.org, joel@....id.au,
	linux-arm-kernel@...ts.infradead.org, lorenzo.pieralisi@....com,
	khilman@...aro.org, moritz.fischer@...us.com,
	linux-kernel@...r.kernel.org, mark.rutland@....com
Subject: Re: [PATCH v1 0/6] misc: add reboot mode driver

Hi,

On 22/12/2015 at 17:02:29 +0800, Andy Yan 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 vendor specific write interfae
> to store the boot mode in some place like special register
> or sram , which can be read by the bootloader after system
> reboot.
> 
> This is commonly done on Android based devices, in order to
> reboot the device into fastboot or recovery mode.
> 
> Before this patch , I have try some hack on[0], and then found
> John Stultz also doing the same work[1].
> 
> As John is busy these days, I go on with this work.
> 
> [0]https://patchwork.kernel.org/patch/7647751/
> [1]https://patchwork.kernel.org/patch/7802391/
> 
> Changes in v1:
> - fix the embarrassed compile warning
> - correct the maskrom magic number
> - check for the normal reboot
> - correct the maskrom magic number
> - use macro defined in rockchip_boot-mode.h for reboot-mode DT node
> 
> Andy Yan (6):
>   dt-bindings: misc: add document for reboot-mode driver
>   dt-bindings: soc: add document for rockchip reboot-mode driver
>   misc: add reboot mode driver
>   soc: rockchip: add reboot mode driver
>   ARM: dts: rockchip: add reboot-mode node
>   ARM64: dts: rockchip: add reboot-mode node
> 

This seems nice and useful, some further ideas:

>  .../devicetree/bindings/misc/reboot-mode.txt       | 41 +++++++++
>  .../bindings/soc/rockchip/rockchip,reboot-mode.txt | 39 +++++++++
>  arch/arm/boot/dts/rk3288.dtsi                      | 26 ++++++
>  arch/arm/boot/dts/rk3xxx.dtsi                      | 26 ++++++
>  arch/arm64/boot/dts/rockchip/rk3368.dtsi           | 26 ++++++
>  drivers/misc/Kconfig                               |  7 ++
>  drivers/misc/Makefile                              |  1 +
>  drivers/misc/reboot_mode.c                         | 96 ++++++++++++++++++++++

I think this actually belongs to drivers/power/reset/ instead of misc

>  drivers/soc/rockchip/Kconfig                       |  9 ++
>  drivers/soc/rockchip/Makefile                      |  1 +
>  drivers/soc/rockchip/reboot.c                      | 68 +++++++++++++++

And maybe that part could be made generic instead of rockchip specific.
It simply uses a regmap to do the accesses, I guess a lot of other
platforms will do that. We have syscon-reboot and syscon-poweroff for example.

I think then we can extend the "framework" by having generic drivers to
store the value in eeprom or nvram for example.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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