Message-ID: <20130902085225.GF27891@e106331-lin.cambridge.arm.com>
Date:	Mon, 2 Sep 2013 09:52:25 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Pawel Moll <Pawel.Moll@....com>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"ian.campbell@...rix.com" <ian.campbell@...rix.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"nobuhiro.iwamatsu.yj@...esas.com" <nobuhiro.iwamatsu.yj@...esas.com>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	"rob@...dley.net" <rob@...dley.net>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 2/2] sh_eth: add device tree support

On Sat, Aug 31, 2013 at 01:29:33AM +0100, Sergei Shtylyov wrote:
> Add support of the device tree probing for the Renesas SH-Mobile SoCs.
> 
> This work is loosely based on an original patch by Nobuhiro Iwamatsu
> <nobuhiro.iwamatsu.yj@...esas.com>.
> 
> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
> 
> ---
> This patch is against Dave's 'net-next.git' repo.
> 
>  Documentation/devicetree/bindings/net/sh_eth.txt |   40 +++++++++++++
>  drivers/net/ethernet/renesas/sh_eth.c            |   66 ++++++++++++++++++++++-
>  2 files changed, 105 insertions(+), 1 deletion(-)
> 
> Index: net-next/Documentation/devicetree/bindings/net/sh_eth.txt
> ===================================================================
> --- /dev/null
> +++ net-next/Documentation/devicetree/bindings/net/sh_eth.txt
> @@ -0,0 +1,40 @@
> +* Renesas Electronics SH EtherMAC
> +
> +This file provides information on what the device node for the SH EtherMAC
> +interface contains.
> +
> +Required properties:
> +- compatible: "renesas,gether-r8a7740" if the device is a part of R8A7740 SoC.
> +	      "renesas,ether-r8a7779" if the device is a part of R8A7778/9 SoCs.
> +	      "renesas,ether-r8a7790" if the device is a part of R8A7790/1 SoCs.

What are the functional differences between the blocks in these devices
that mean they have different compatible strings?

> +- reg: offset and length of the register set for the device; if the device has
> +       TSU registers, you need to specify two register sets here.

This doesn't explicitly state ordering, and doesn't describe what the
first register set is (control registers?). If possible, it would be
nice to refer to the set of registers by the name given in
documentation; is there any available?

I think we should have something like the below to ensure it's explicit.
In general we need more consistency in the the way bindings describe reg
properties.

	- reg: offset and length of:
	     [1] the control registers of the device (required)
	     [2] the TSU registers for the device (optional)

> +- interrupt-parent: the phandle for the interrupt controller that services
> +		    interrupts for this device.

Why is that required?

> +- interrupts: interrupt mapping for the interrupt source.

Interrupts are defined in terms of interrupt-specifiers. How about:

	- interrupts: an interrupt-specifier for the sole interrupt
	              generated by the device.

> +- phy-mode: string, operation mode of the PHY interface (a string that
> +	    of_get_phy_mode() can understand).

That looks suspicious. Bindings should *not* refer to Linux internals.
Instead, we should document the phy-handle and phy-mode properties and
how they are meant to be used in a generic binding document (I couldn't
see a generic document doing this so far...).

> +- phy-handle: phandle of the PHY device.
> +
> +Optional properties:
> +- local-mac-address: 6 bytes, MAC address.
> +- renesas,no-ether-link: specify when a board does not provide a proper LINK
> +			 signal.
> +- renesas,ether-link-active-low: specify when the LINK signal is active-low.

What types are these? I know local-mac-address is a byte-string by
ePAPR, presumably the last two are empty (boolean)?

> +
> +Example (Armadillo800EVA board):
> +
> +	ethernet@...00000 {
> +		compatible = "renesas,gether-r8a7740";
> +		reg = <0xe9a00000 0x800>, <0xe9a01800 0x800>;
> +		interrupt-parent = <&gic>;
> +		interrupts = <0 142 0x4>;
> +		phy-mode = "mii";
> +		phy-handle = <&phy0>;
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		phy0: ethernet-phy@0 {
> +			reg = <0>;
> +		};

The binding didn't state anything about sub-nodes. Is it a general
property of phy bindings that they may be embedded within a consumer's
node?

> +	};
> Index: net-next/drivers/net/ethernet/renesas/sh_eth.c
> ===================================================================
> --- net-next.orig/drivers/net/ethernet/renesas/sh_eth.c
> +++ net-next/drivers/net/ethernet/renesas/sh_eth.c
> @@ -32,6 +32,9 @@
>  #include <linux/platform_device.h>
>  #include <linux/mdio-bitbang.h>
>  #include <linux/netdevice.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_net.h>
>  #include <linux/phy.h>
>  #include <linux/cache.h>
>  #include <linux/io.h>
> @@ -2600,6 +2603,52 @@ static const struct net_device_ops sh_et
>  	.ndo_change_mtu		= eth_change_mtu,
>  };
>  
> +#ifdef CONFIG_OF
> +static struct sh_eth_plat_data *sh_eth_parse_dt(struct device *dev)
> +{
> +	struct device_node *np = dev->of_node;
> +	struct sh_eth_plat_data *pdata;
> +	struct device_node *phy;
> +	const char *mac_addr;
> +
> +	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
> +	if (!pdata)
> +		return NULL;
> +
> +	pdata->phy_interface = of_get_phy_mode(np);
> +
> +	phy = of_parse_phandle(np, "phy-handle", 0);
> +	if (!phy || of_property_read_u32(phy, "reg", &pdata->phy)) {

NAK. You didn't describe the format of the phy node, yet you are reading
values from it from a logically separate driver.

Thanks,
Mark.
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