[U-Boot] [linux-sunxi] Re: [PATCH] sunxi: Fix gmac not working reliable on the Bananapi

[Hans de Goede]

Hi,

On 09/29/2014 08:35 PM, jonsmirl at gmail.com wrote:
> On Mon, Sep 29, 2014 at 2:16 PM, Karsten Merker <merker at debian.org> wrote:
>> On Mon, Sep 29, 2014 at 09:13:37AM +0300, Siarhei Siamashka wrote:
>>> How did you come to the idea to poke these bits?
>>
>> The linux 3.4 kernel from https://github.com/LeMaker/linux-bananapi
>> (which is a patched linux-sunxi.org 3.4 kernel) does not show this
>> problem, so we started looking into what is different there, and the
>> relevant change that was found was setting these particular
>> undocumented bits.
> 
> File at issue here asking for the documentation
> https://github.com/allwinner-zh/documents

I'm already talking to Allwinner about this, it seems that bits
10-11, or more likely 10-12 of the gmac clk register are the tx
equivalent of bits 5-7, "Configure GMAC receive clock delay
chain". I think this is there to deal with the pcb data and clk
traces not having the same length, so that this is highly board
specific. I'm waiting on confirmation on this from Allwinner,
as well as some info on the unit of this 0-7 value.

Regards,

Hans