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

Ben Warren
2009-07-21T07:46:49Z

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 :)

Ben