linux-kernel - Re: [PATCH V2 1/6] Documentation: add dts binding for X-Gene reboot dts node.

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Message-Id: <201401132043.52491.arnd@arndb.de>
Date:	Mon, 13 Jan 2014 20:43:51 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Feng Kan <fkan@....com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH V2 1/6] Documentation: add dts binding for X-Gene reboot dts node.

On Monday 13 January 2014, Feng Kan wrote:
> FKAN: I could remove this dts node and create another dts node that
> describe the range of registers on the SCU and use that node in this driver.
> I am not sure which subsystem I can use to handle this case, I do see a reset
> subsystem in the kernel but more used for ip resets. Please kindly let
> me know. Thanks for the great feedback.

Is this related to the standard ARM SCU that manages multiprocessor
systems, or a different unit that uses the same name?

Since this is a global register range with a variety of things in it,
the best candidate IMHO would be to use the "syscon" driver. You can
mark the device node as 'compatible="apm,xgene-scu","syscon"' to let
it get picked up by the drivers/mfd/syscon driver, which creates
a "regmap" structure for it.

The reset driver then uses a DT reference with a phandle to the
SCU node and calls syscon_regmap_lookup_by_phandle() to get the
regmap. It can get the register number inside the regmap from DT
as well and use the regmap API to perform the reset.

	Arnd
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