[U-Boot] [PATCH v2 5/9] AVR32: macb - Disable 100mbps if clock is slow

[Ben Warren]

Hi Gunnar,


Gunnar Rangøy wrote:
> On Fri, Jan 23, 2009 at 4:38 PM, Jean-Christophe PLAGNIOL-VILLARD
> <plagnioj at jcrosoft.com> wrote:
>   
>> On 12:56 Fri 23 Jan     , Gunnar Rangoy wrote:
>>     
>>> From: Olav Morken <olavmrk at gmail.com>
>>>
>>> For 100mbps operation, the ethernet controller requires a 25 MHz clock
>>> in MII mode, and a 50 MHz clock in RMII mode. If the clock is slower,
>>> disable 100 Mbps mode.
>>>
>>> Signed-off-by: Gunnar Rangoy <gunnar at rangoy.com>
>>> Signed-off-by: Paul Driveklepp <pauldriveklepp at gmail.com>
>>> Signed-off-by: Olav Morken <olavmrk at gmail.com>
>>> ---
>>>  drivers/net/macb.c |   12 +++++++++++-
>>>  1 files changed, 11 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/net/macb.c b/drivers/net/macb.c
>>> index 08bebf7..d47a052 100644
>>> --- a/drivers/net/macb.c
>>> +++ b/drivers/net/macb.c
>>> @@ -297,7 +297,17 @@ static void macb_phy_reset(struct macb_device *macb)
>>>       int i;
>>>       u16 status, adv;
>>>
>>> -     adv = ADVERTISE_CSMA | ADVERTISE_ALL;
>>> +     adv = ADVERTISE_CSMA | ADVERTISE_ALL ;
>>>       
>> ??
>>     
>
> Oops... Will fix this.
>
>   
>>> +
>>> +#ifdef CONFIG_MACB_FORCE10M
>>> +     printf("%s: 100Mbps is not supported on this board - forcing 10Mbps.\n",
>>> +            netdev->name);
>>> +
>>> +     adv &= ~ADVERTISE_100FULL;
>>> +     adv &= ~ADVERTISE_100HALF;
>>> +     adv &= ~ADVERTISE_100BASE4;
>>> +#endif
>>>       
>>        not a fan
>>        could you be more specific about the problem?
>>
>> Best Regards,
>> J.
>>
>>     
>
> On the EVK1100 board, the CPU (UC3A0512) is connected to the PHY via an
> RMII bus. This requires the CPU clock to be at least 50 MHz.
> Unfortunately, the chip on current EVK1100 boards may be unable to run
> at more than 50 MHz, and with the oscillator on the board, the closest
> frequency we can generate is 48 MHz.
>
> This patch makes it possible to limit the macb to 10 MBit for this
> case. We are open for suggestions for other solutions.
>
>   
How about using a PHY capability override CONFIG.  Something like this:

#if defined(CONFIG_MACB_PHY_CAPAB)    <-- insert better name here
adv = ADVERTISE_CSMA | CONFIG_MACB_PHY_CAPAB;
#else
adv = ADVERTISE_CSMA | ADVERTISE_ALL
#endif

Just an idea...

regards,
Ben