netdev - Re: [PATCH V4 1/8] sxgbe: Add device-tree binding support document

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Message-ID: <20140318091852.GA8043@e106331-lin.cambridge.arm.com>
Date:	Tue, 18 Mar 2014 09:18:53 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Byungho An <bh74.an@...sung.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"ilho215.lee@...sung.com" <ilho215.lee@...sung.com>,
	"siva.kallam@...sung.com" <siva.kallam@...sung.com>,
	"vipul.pandya@...sung.com" <vipul.pandya@...sung.com>,
	"ks.giri@...sung.com" <ks.giri@...sung.com>
Subject: Re: [PATCH V4 1/8] sxgbe: Add device-tree binding support document

Hi,

As a general note it's helpful for devicetree to be Cc'd on the entire
series (though the binding document should be a separate patch) as it
provides useful context for reviewing the binding.

On Tue, Mar 18, 2014 at 06:47:13AM +0000, Byungho An wrote:
> From: Siva Reddy <siva.kallam@...sung.com>
> 
> This patch adds binding document for SXGBE ethernet driver via device-tree.
> 
> Signed-off-by: Siva Reddy Kallam <siva.kallam@...sung.com>
> Signed-off-by: Byungho An <bh74.an@...sung.com>
> ---
>  .../devicetree/bindings/net/samsung-sxgbe.txt      |   53
> ++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/net/samsung-sxgbe.txt
> 
> diff --git a/Documentation/devicetree/bindings/net/samsung-sxgbe.txt
> b/Documentation/devicetree/bindings/net/samsung-sxgbe.txt
> new file mode 100644
> index 0000000..ca27947
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/samsung-sxgbe.txt
> @@ -0,0 +1,53 @@
> +* Samsung 10G Ethernet driver (SXGBE)
> +
> +Required properties:
> +- compatible: Should be "samsung,sxgbe-v2.0a"
> +- reg: Address and length of the register set for the device
> +- interrupt-parent: Should be the phandle for the interrupt controller
> +  that services interrupts for this device
> +- interrupts: Should contain the SXGBE interrupts
> +  These interrupts are ordered by fixed and follows variable
> +  trasmit DMA interrupts, receive DMA interrupts and lpi interrupt.
> +  index 0 - this is fixed common interrupt of SXGBE and it is always
> +  available.
> +  index 1 to 25 - 8 variable trasmit interrupts, variable 16 receive
> interrupts
> +  and 1 optional lpi interrupt.
> +- phy-mode: String, operation mode of the PHY interface.
> +  Supported values are: "xaui", "gmii".
> +- samsung,pbl: Integer, Programmable Burst Length.
> +  Supported values are 1, 2, 4, 8, 16, or 32.

There's no need to abbreviate to "pbl".

Is this a property of the hardware, or configuration that the kernel
will program in? If the latter, why can the kernel not choose?

> +- samsung,fixed-burst: Boolean, Program the DMA to use the fixed burst mode
> +- samsung,burst-map: Integer, Program the possible bursts supported by sxgbe
> +  This is an interger and represents allowable DMA bursts when fixed burst.
> +  Allowable range is 0x00-0x3F. This field is valid only when fixed burst is
> +  enabled, otherwise ignored.

If that's the case, why not have just this property and have it imply
the use of fixed burst mode?

When is it necessary to use fixed burst mode?

> +- samsung,adv-addr-mode: Boolean, Program the DMA to use Enhanced address
> mode.

When would this be selected, and why can the kernel not choose?

> +- samsung,force_thresh_dma_mode: Boolean, Force DMA to use the threshold mode
> +  for both tx and rx

s/_/-/ in property names.

Likewise, why can the kernel not choose.

> +- samsung,force_sf_dma_mode: Boolean, Force DMA to use the Store and Forward
> +  mode for both tx and rx. This flag is ignored if force_thresh_dma_mode is
> set.

Likewise for both points.

> +- samsung,phy-addr: Integer, Address of the PHY attached with SXGBE.

Some of these properties appear to be missing from the example. Are they
required or optional?

Thanks,
Mark.

> +
> +Optional properties:
> +- mac-address: 6 bytes, mac address
> +
> +Example:
> +
> +	aliases {
> +		ethernet0 = <&sxgbe0>;
> +	};
> +
> +	sxgbe0: ethernet@...40000 {
> +		compatible = "samsung,sxgbe-v2.0a";
> +		reg = <0 0x1a040000 0 0x10000>;
> +		interrupt-parent = <&gic>;
> +		interrupts = <0 209 4>, <0 185 4>, <0 186 4>, <0 187 4>,
> +			     <0 188 4>, <0 189 4>, <0 190 4>, <0 191 4>,
> +			     <0 192 4>, <0 193 4>, <0 194 4>, <0 195 4>,
> +			     <0 196 4>, <0 197 4>, <0 198 4>, <0 199 4>,
> +			     <0 200 4>, <0 201 4>, <0 202 4>, <0 203 4>,
> +			     <0 204 4>, <0 205 4>, <0 206 4>, <0 207 4>,
> +			     <0 208 4>, <0 210 4>;
> +		mac-address = [000000000000]; /* Filled in by U-Boot */
> +		phy-mode = "xaui";
> +	};
> -- 
> 1.7.10.4
> 
> 
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