[U-Boot] [PATCH] Bugfix: mpc512x_fec MII accesses fail after ethernet transfers

[Ben Warren <biggerbadderben@gmail.com>]

Wolfgang Denk wrote:
> Dear Ben Warren,
>
> In message <4A6565D4.7050400@gmail.com> you wrote:
>   
>> Thomas D?rfler wrote:
>>     
>>> The mpc512x FEC network driver resets the FEC before transferring
>>> packets. With this reset, the FEC clears the previous setting of MII
>>> transfer speed. This patch ensures, that it is set again to a reasonable
>>> value after a FEC reset.
>>>
>>> Signed-off-by: Thomas Doerfler <Thomas.Doerfler@embedded-brains.de>
>>> --
>>> diff --git a/drivers/net/mpc512x_fec.c b/drivers/net/mpc512x_fec.c
>>> index fb2c19a..f3d76ba 100644
>>> --- a/drivers/net/mpc512x_fec.c
>>> +++ b/drivers/net/mpc512x_fec.c
>>> @@ -446,6 +446,19 @@ static void mpc512x_fec_halt (struct eth_device *dev)
>>>          * wait at least 16 clock cycles
>>>          */
>>>         udelay (10);
>>> +       /*
>>> +        * NOTE: reset will also clear the MII speed register
>>> +        * we should reinitialize it ASAP
>>> +        */
>>> +       if (fec->xcv_type != SEVENWIRE) {
>>> +               /*
>>> +                * Set MII_SPEED = (1/(mii_speed * 2)) * System Clock
>>> +                * and do not drop the Preamble.
>>> +                */
>>> +               fec->eth->mii_speed = ((((gd->ips_clk / 1000000) / 5)
>>> +                                       + 1)
>>> +                                      << 1);
>>> +       }
>>>  #if (DEBUG & 0x3)
>>>         printf ("Ethernet task stopped\n");
>>>  #endif
>>>   
>>>       
>> Applied to net repo (after some tweaking)
>>     
>
> Sorry Ben, but I am not convinced that this is a good way to  address
> the problem. Please see the previous discussion of this patch.
>
> I think it  is  perfectly  reasonable  that  mpc512x_fec_halt()  also
> disables  the  MII  clock.  After  all,  when the network intrface is
> stopped, there is no need that the clocks keep  running  and  drawing
> current on battery powered devices.
>
> I'd rather see that the MII clock gets only started when needed, i. e.
> before running any MII commands.
>
> Best regards,
>
> Wolfgang Denk
>
>   
Yikes, sorry again.  I saw the one where you said 'thanks for the
explanation, I can reproduce...'

Better hold off on my pull request :)

On that note, I'm off to bed.  Hopefully the brain is better engaged 
tomorrow.

Ben