[U-Boot] [PATCH 3/7] fec_imx27: driver for FEC ethernet controller on i.MX27

[alfred steele]

On Mon, Nov 16, 2009 at 8:59 PM, Ben Warren <biggerbadderben at gmail.com> wrote:
> Hi Alfred,
>
> alfred steele wrote:
>>>
>>> Thanks for your submission!
>>>
>>
>> What is the current design on the mxc fec interface's attainment of a
>> MAC address. From the kernel driver it looks like it looks at the
>> IIM(IC identification registers) on the MXC platform(like mx51/35) to
>> look for a programmed mac address and then the set the fec mac to the
>> same .
>>
>> Looks like with the current mxc_fec driver there is not support for
>> the same. I am thinking of a mechanism to hardcode a fake MAC which
>> would subsequently be picked up by the kernel without using the
>> bd_info structure.
>> Any comments/suggestions?
>>
>> -Alfred.
>>
>
> I don't know much about this driver, but it appears to be doing things
> incorrectly.  The correct flow is as follows.  It is documented in
> 'doc/README.enetaddr':
>
> 1. The driver's initialize() function read from NVRAM if available.  MAC
> address is stuffed into dev->enetaddr.  The initialize() function should not
> try to get the address from the environment, which is where the imx27 driver
> goes wrong.
> 2. After all drivers have been initialized, eth_initialize() ( in net/eth.c)
> reads from the environment.  If the value in the environment is valid and
> the value in dev->enetaddr is valid and both are different, the user is
> warned.  The value in the environment overwrites the value in dev->enetaddr
> 3. When a network operation is performed, the driver's init() function is
> called, which is where the address is programmed into the device.
>
> As you can see, if the device is never used, step 3 is never exected and the
> device is never programmed.  This is how it's supposed to work, since the
> U-boot design philosophy dictates that hardware is never touched unless it
> is used in U-boot.  I'm pretty sure hard-coding a fake MAC address would run
> afoul of this rule.
Is there a way to pass the information to kernel using either the
dev->enetaddr  without programming the IIM module register. Would i
have to use bd_info structure or can we do without it.? This problem
is specific to the mx27 i guess.
-Alfred