linux-kernel - Re: [PATCH v3 1/7] mfd: add syscon driver based on regmap

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Date:	Wed, 29 Aug 2012 10:00:50 +0800
From:	Dong Aisheng <b29396@...escale.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
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	<broonie@...nsource.wolfsonmicro.com>,
	Zhao Richard-B20223 <B20223@...escale.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [PATCH v3 1/7] mfd: add syscon driver based on regmap

On Wed, Aug 29, 2012 at 06:54:00AM +0800, Stephen Warren wrote:
> On 08/28/2012 02:09 AM, Dong Aisheng wrote:
> > From: Dong Aisheng <dong.aisheng@...aro.org>
> > 
> > Add regmap based syscon driver.
> > This is usually used for access misc bits in registers which does not belong
> > to a specific module, for example, IMX IOMUXC GPR and ANATOP.
> > With this driver, client can use generic regmap API to access registers
> > which are registered into syscon.
> 
> > diff --git a/Documentation/devicetree/bindings/mfd/syscon.txt b/Documentation/devicetree/bindings/mfd/syscon.txt
> 
> > +* System Controller Registers R/W driver
> 
> I think the binding document could use some information about what a
> "syscon" actually is, especially since the compatible value is something
> generic like "syscon" rather than something with a vendor-specific
> prefix.
Yes, we'd better have it.

> How about:
> 
> A system controller node represents a register region containing a set
> of miscellaneous registers. The registers are not cohesive enough to
> represent as any specific type of device. The typical use-case is for
> some other node's driver, or platform-specific code, to acquire a
> reference to the syscon node (e.g. by phandle, node path, or search
> using a specific compatible value), interrogate the node (or associated
> OS driver) to determine the location of the registers, and access the
> registers directly.
> 
It looks very good to me.
Thanks for the help.

> > +Required properties:
> > +- compatible: Should contain "syscon".
> > +- reg: the register range can be access from syscon
> > +
> > +Examples:
> > +gpr: iomuxc-gpr@...e0000 {
> > +	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
> > +	reg = <0x020e0000 0x38>;
> > +};
> 
> > diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> 
> > +config MFD_SYSCON
> > +        bool "System Controller Register R/W Based on Regmap"
> > +        select REGMAP_MMIO
> > +        help
> > +          Select this option to enable accessing system control registers
> > +	  via regmap.
> 
> I think the indentation is off there.
> 
You're right.
Will fix it.

> > +static int __devinit syscon_probe(struct platform_device *pdev)
> ...
> > +	regcache_cache_only(syscon->regmap, false);
> 
> Isn't that the default?
> 
Correct, will remove.

> Aside from that, I don't have any particular comments on this series, so
> please consider it,
> 
> Acked-by: Stephen Warren <swarren@...dotorg.org>
> 
Thanks a lot.

Regards
Dong Aisheng

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