Subject: Re: [PATCH 2/2] sh_eth: add device tree support

From: Sergei Shtylyov <[email-masked]>
Date: Fri, 06 Sep 2013 23:10:07 +0400

Hello.

On 09/02/2013 12:52 PM, Mark Rutland wrote:

    Don't know why I haven't noticed your mail before...

>> 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
>> <[email-masked]>.

>> Signed-off-by: Sergei Shtylyov <[email-masked]>

>> ---
>> 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?

     RA87740 has Gigabit Ether (GEther) with TSU block (I don't know what TSU 
stands for) and the register layout completely different from the other SoCs. 
R8A777x and R8A7790 are 100 Mbit/s Ether without TSU block differing in some 
minor but vital register details between them; they use so called "R-Car" 
register layout contrasted to the "Gigabit" layout of R8A7740.

>> +- 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?

    No, there's not common name (and I only have R8A777x and R8A7790 docs).
There are two subranges for those SoCs: HDMAC and feLic registers at offsets 
0x200 and 0x300 from the "reg" prop start.

> 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)

    OK.

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

> Why is that required?

    I'm not sure, maybe it's not.

>> +- 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.

    OK.

>> +- 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

    There's also "phy" variant in use now in addition to the older 
"phy-handle". Sigh...

> how they are meant to be used in a generic binding document (I couldn't
> see a generic document doing this so far...).

    So you want me to create one?

>> +- 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)?

    Exactly.

>> +
>> +Example (Armadillo800EVA board):
>> +
>> +	ethernet@e9a00000 {
>> +		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?

    Considering Ethernet PHY subnodes, yes. They hang off MDIO bus controlled 
by the Ethernet MAC registers.

>> +	};
>> 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
[...]
>> @@ -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.

    See Documentation/devicetree/bindings/net/phy.txt. Although I really 
didn't follow it closely (and it looks pretty obsolete, requiring 
"device_type" and "linux,phandle" props).

> Thanks,
> Mark.

WBR, Sergei