[U-Boot] [PATCH v1 0/5]

[Stefano Babic <sbabic@denx.de>]

Hi Thomas,

On 02/09/2013 16:59, thomas.langer at lantiq.com wrote:
> Hello Stefano,
> 
> Stefano Babic wrote on 2013-09-02:
> 
>> Some phys have additional registers that are not covered
>> by standard. Access to this registers can be done via
>> specific sequence according to the phy datasheet.
>> The driver for Micrel phy contains some additional function,
>> that the board maintainer can call to tune the phy. However,
>> these registers cannot be accessed with "mmdio" command.
>>
>> Add calback to the phy API to allow to call the function
>> for reading / writing extended registers with the mmdio command.
>>
>>
> 
> The basic mechanism used for the access is not specific to Micrel, it is defined 
> in the IEEE standard [1], "Annex 22D: Clause 22 access to Clause 45 MMD registers"

Interesting - my changes were done according to the Micrel's KSZ9031
datasheet.

> 
> A presentation for this can be found when you ask google for it [2]
> 
> [1]: IEEE Std 802.3-2008 (or 2012): http://standards.ieee.org/about/get/802/802.3.html
> [2]: https://www.google.de/search?q=%22Clause+22+Access+to+Clause+45+Registers%22
> 
> So maybe it will be useful to have the access functions in the common phy lib?
> 

Maybe it is enough to move the extread / extwrite functions inside
phylib. However, if the behavior of the KSZ9031 matches the
documentation you have posted, the KSZ9021 seems to slightly deviate. Or
is the 9021 supporting another "clause" ?

> I assume that most current PHYs have these method implemented,
> as also some extended standard registers needs this.
> For example, the EEE (Energy Efficient Ethernet) registers are located in this extended
> register range.

This is also a nice to have feature.

> 
> Probably this can be extended in some follow-up patches, 

Let's wait for Joe's opinion.

> I just wanted to share my thoughts ;-)

Thanks, I was not aware of the standard. Learned something new...

Best regards,
Stefano

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