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

[Wolfgang Denk]

Dear Ben Warren,

In message <4A6565D4.7050400 at gmail.com> you wrote:
> 
> Thomas Dörfler 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 at 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

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