linux-kernel - Re: [PATCH v2 2/3] netdev/of/phy: Add MDIO bus multiplexer support.

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Message-ID: <4E835C71.1010108@cavium.com>
Date:	Wed, 28 Sep 2011 10:42:09 -0700
From:	David Daney <david.daney@...ium.com>
To:	Michał Mirosław <mirqus@...il.com>
CC:	devicetree-discuss@...ts.ozlabs.org, grant.likely@...retlab.ca,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	davem@...emloft.net
Subject: Re: [PATCH v2 2/3] netdev/of/phy: Add MDIO bus multiplexer support.

On 09/28/2011 10:32 AM, Michał Mirosław wrote:
> W dniu 28 września 2011 18:51 użytkownik David Daney
> <david.daney@...ium.com>  napisał:
>> On 09/28/2011 12:25 AM, Michał Mirosław wrote:
>>>
>>> 2011/9/28 David Daney<david.daney@...ium.com>:
>>> [...]
>>>>
>>>> +Example :
>>>> +
>>>> +       /* The parent MDIO bus. */
>>>> +       smi1: mdio@...0000001900 {
>>>> +               compatible = "cavium,octeon-3860-mdio";
>>>> +               #address-cells =<1>;
>>>> +               #size-cells =<0>;
>>>> +               reg =<0x11800 0x00001900 0x0 0x40>;
>>>> +       };
>>>> +
>>>> +       /*
>>>> +          An NXP sn74cbtlv3253 dual 1-of-4 switch controlled by a
>>>> +          pair of GPIO lines.  Child busses 2 and 3 populated with 4
>>>> +          PHYs each.
>>>> +        */
>>>> +       mdio-mux {
>>>> +               compatible = "cavium,mdio-mux-sn74cbtlv3253",
>>>> "cavium,mdio-mux";
>>>> +               gpios =<&gpio1 3 0>,<&gpio1 4 0>;
>>>> +               mdio-parent-bus =<&smi1>;
>>>> +               #address-cells =<1>;
>>>> +               #size-cells =<0>;
>>>
>>> This should probably have 'compatible = "nxp,sn74cbtlv3253";' here.
>>>
>>
>> No, the sn74cbtlv3253 is a general purpose part that could be used to
>> multiplex anything (I2C, SPI, random analog signals, etc.).  Only when it is
>> in the "cavium,mdio-mux-sn74cbtlv3253" configuration is it an MDIO bus
>> multiplexer.
>
> This should use some generic name then. 'mdio-mux-gpio' or something.
> There's no point in introducing chip's model for a gate-like discrete
> device.

That could be.  We could define an "mdio-mux-gpio" as something that 
selects the child bus based on the binary encoded value presented on the 
GPIO lines.

I will regenerate the patch set with this in mind.  Note that the only 
part of this patch that will change is this mdio-mux.txt file, no actual 
code is affected.  In patch 3/3 I will add "mdio-mux-gpio" to the 
.of_match_table.

Thanks,
David Daney
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