linux-kernel - Re: [PATCHv7 2/3] devicetree: Addition of the Altera SDRAM EDAC.

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Date:	Thu, 26 Jun 2014 10:45:07 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	"tthayer@...era.com" <tthayer@...era.com>
Cc:	"robherring2@...il.com" <robherring2@...il.com>,
	Pawel Moll <Pawel.Moll@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"rob@...dley.net" <rob@...dley.net>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"dinguyen@...era.com" <dinguyen@...era.com>,
	"dougthompson@...ssion.com" <dougthompson@...ssion.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"bp@...en8.de" <bp@...en8.de>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"tthayer.linux@...il.com" <tthayer.linux@...il.com>
Subject: Re: [PATCHv7 2/3] devicetree: Addition of the Altera SDRAM EDAC.

On Wed, Jun 25, 2014 at 10:15:26PM +0100, tthayer@...era.com wrote:
> From: Thor Thayer <tthayer@...era.com>
> 
> Add the Altera SDRAM EDAC bindings and device tree changes to the Altera SoC project.
> 
> Signed-off-by: Thor Thayer <tthayer@...era.com>
> ---
> v2: Changes to SoC EDAC source code.
> 
> v3: Fix typo in device tree documentation.
> 
> v4,v5: No changes - bump version for consistency.
> 
> v6: Assign ECC registers in SDRAM controller to EDAC
> 
> v7: Fix SDRAM EDAC base address.
> ---
>  .../bindings/arm/altera/socfpga-sdram-edac.txt     |   15 +++++++++++++++
>  arch/arm/boot/dts/socfpga.dtsi                     |    6 ++++++
>  2 files changed, 21 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/altera/socfpga-sdram-edac.txt
> 
> diff --git a/Documentation/devicetree/bindings/arm/altera/socfpga-sdram-edac.txt b/Documentation/devicetree/bindings/arm/altera/socfpga-sdram-edac.txt
> new file mode 100644
> index 0000000..d68e033
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/altera/socfpga-sdram-edac.txt
> @@ -0,0 +1,15 @@
> +Altera SOCFPGA SDRAM Error Detection & Correction [EDAC]
> +
> +Required properties:
> +- compatible : should contain "altr,sdram-edac";
> +- reg : should contain the ECC register range in sdram
> +        controller (address and length).
> +- interrupts : Should contain the SDRAM ECC IRQ in the
> +	appropriate format for the IRQ controller.
> +
> +Example:
> +	sdramedac@...2502c {
> +		compatible = "altr,sdram-edac";
> +		reg = <0xffc2502c 0x28>;
> +		interrupts = <0 39 4>;
> +	};
> diff --git a/arch/arm/boot/dts/socfpga.dtsi b/arch/arm/boot/dts/socfpga.dtsi
> index 310292e..da0785d 100644
> --- a/arch/arm/boot/dts/socfpga.dtsi
> +++ b/arch/arm/boot/dts/socfpga.dtsi
> @@ -687,6 +687,12 @@
>  			reg = <0xffc25000 0x4>;
>  		};
>  
> +		sdramedac@...2502c {
> +			compatible = "altr,sdram-edac";
> +			reg = <0xffc2502c 0x28>;
> +			interrupts = <0 39 4>;
> +		};

I'm not sure I understand this. The ECC register existing within the
SDRAM controller, which we have a binding for. Why do we need a separate
binding for a subset of registers within an IP block?

Why can we not have a single binding for the entire SDRAM controlelr and
decompse that within Linux as it makes sense for the appropriate
subsystyems?

Leaking Linux design into bindings is a bad idea; it makes it harder to
change things.

Mark.
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