linux-kernel - Re: [PATCH v2 07/11] ARM:stixxxx: Add STiH416 SOC support

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Date:	Mon, 10 Jun 2013 15:52:07 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Srinivas KANDAGATLA <srinivas.kandagatla@...com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	devicetree-discuss@...ts.ozlabs.org,
	Grant Likely <grant.likely@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux@....linux.org.uk, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Mark Brown <broonie@...nel.org>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Olof Johansson <olof@...om.net>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Stephen Gallimore <stephen.gallimore@...com>,
	Stuart Menefy <stuart.menefy@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Prisk <linux@...sktech.co.nz>
Subject: Re: [PATCH v2 07/11] ARM:stixxxx: Add STiH416 SOC support

On Monday 10 June 2013 10:27:05 Srinivas KANDAGATLA wrote:

> +	soc {
> +		pin-controller-sbc {
> +			#address-cells	= <1>;
> +			#size-cells	= <1>;
> +			compatible	= "st,stih416-pinctrl", "simple-bus";

Why is this both its own device with a compatible string and a
"simple-bus" at the same time? Wouldn't it be simpler to just
scan the child device nodes from the "st,stih416-pinctrl"
driver instead of having a separate platform_driver for them?

> +			st,retime-in-delay	= <0 300 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250>;
> +			st,retime-out-delay	= <0 300 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250>;
> +			st,syscfg		= <&syscfg_sbc>;
> +			st,syscfg-offsets	= <0 40 50 60 100>;
> +			ranges;
> +			PIO0: pinctrl@...10000 {
> +				#gpio-cells = <1>;
> +				compatible = "st,stixxxx-gpio";
> +				gpio-controller;
> +				reg = <0xfe610000 0x100>;
> +				st,bank-name  = "PIO0";
> +				st,retime-pin-mask = <0xff>;
> +			};
> +			PIO1: pinctrl@...11000 {
> +				#gpio-cells	= <1>;
> +				compatible	= "st,stixxxx-gpio";
> +				gpio-controller;
> +				reg = <0xfe611000 0x100>;
> +				st,bank-name  = "PIO1";
> +				st,retime-pin-mask = <0xff>;
> +			};

What is in the ranges between these registers? It seems you have
256 bytes for each pinctrl node, with 4kb spacing. I wonder if
it would make sense to declare the entire range to belong to a single
pinctrl device. At least since all of the registers are in a single
range, you could add a property like

	ranges = <0 0xfe610000 0x10000>;

and use relative addresses in the sub-nodes.

Please don't use identifiers with 'xxx' in them. Instead use numbers
of actual chips, ideally using the first one that this is compatible
with.

> +		syscfg_sbc:syscfg@...00000{
> +			compatible	= "st,stih416-syscfg";
> +			reg		= <0xfe600000 0x1000>;
> +			syscfg-range	= <0 999>;
> +			syscfg-name	= "SYSCFG_SBC";
> +		};
> +		syscfg_front:syscfg@...10000{
> +			compatible	= "st,stih416-syscfg";
> +			reg		= <0xfee10000 0x1000>;
> +			syscfg-range	= <1000 999>;
> +			syscfg-name	= "SYSCFG_FRONT";
> +		};

Did you mean to declare ranges excluding 1000 and 2000 here?
Normally I would expect inclusive ranges like syscfg-range=<0 1000>;

What is the idea of the 'syscfg-name'? If the nodes are all different,
I would expect them to have distinct "compatible" values and not
need them.

	Arnd
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