netdev - RE: davinci_emac/mdio: SOFT_RESET of EMAC module resets MDIO on AM1808

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Date:	Mon, 27 Feb 2012 10:15:03 +0000
From:	"Rajashekhara, Sudhakar" <sudhakar.raj@...com>
To:	Christian Riesch <christian.riesch@...cron.at>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davinci-linux-open-source@...ux.davincidsp.com" 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	"Chemparathy, Cyril" <cyril@...com>,
	"Gole, Anant" <anantgole@...com>
Subject: RE: davinci_emac/mdio: SOFT_RESET of EMAC module resets MDIO on
 AM1808

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@...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:
> >>

[snip]

> >>
> >> According to the AM1808 Technical Reference Manual (sections 18.2.14.1
> >> and 18.3.3.34 in [1]), 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.

Regards,
Sudhakar
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