davinci_emac/mdio: SOFT_RESET of EMAC module resets MDIO on AM1808
sudhakar.raj at ti.com
Mon Feb 27 23:46:08 CST 2012
On Mon, Feb 27, 2012 at 15:44:54, Rajashekhara, Sudhakar wrote:
> Hi Christian,
> On Fri, Feb 24, 2012 at 19:45:23, Christian Riesch wrote:
> > Hello Sudhakar,
> > On Fri, Feb 24, 2012 at 2:02 PM, Rajashekhara, Sudhakar <sudhakar.raj at ti.com> wrote:
> > > On Thu, Feb 23, 2012 at 14:39:49, Christian Riesch wrote:
> > >> Hi,
> > >> I observed this behavior on a Texas Instruments AM1808 SoC (AM1808
> > >> experimenter's kit) running the current mainline kernel:
> > >>
> > >>
> > >> According to the AM1808 Technical Reference Manual (sections 22.214.171.124
> > >> and 126.96.36.199 in ), writing a 1 to the EMAC_SOFTRESET register
> > >> resets the EMAC module, but not the MDIO module. However, when I
> > >> comment out the code above, the MDIO control register is not affected
> > >> and the warning 'resetting idled controller' disappears.
> > >>
> > >
> > > But this was not the case for me. Even after commenting out the above lines,
> > > I could still see that MDIO was getting reset.
> > Uh, I am sorry. I forgot to mention that there is a second
> > emac_write(EMAC_SOFTRESET,1); in emac_dev_stop() in davinci_emac.c.
> > This one must also be commented out to make the resetting idled controller
> > message go away.
> > The patch below shows that changes that I did. May I please ask you to try
> > again with these changes?
> I was able to reproduce the issue. I'll debug this further and get back to you.
I was going through the mailing list discussions where a work around for emac
soft-reset tie-up to mdio controller has been proposed. I think this was a known
issue on TI's da8xx family of devices. Please refer to the thread at
As you have mentioned in your patch, did you get any confirmation from TI designer
regarding emac soft reset behavior? I see that nothing has been mentioned in the
EMAC user guide.
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