Re: davinci_emac/mdio: SOFT_RESET of EMAC module resets MDIO on AM1808

On Tuesday, February 28, 2012, Rajashekhara, Sudhakar [off-list ref]
wrote:

Hi Christian,

On Mon, Feb 27, 2012 at 15:44:54, Rajashekhara, Sudhakar wrote:

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Hi Christian,

On Fri, Feb 24, 2012 at 19:45:23, Christian Riesch wrote:

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Hello Sudhakar,

On Fri, Feb 24, 2012 at 2:02 PM, Rajashekhara, Sudhakar <

sudhakar.raj-l0cyMroinI0@public.gmane.org> wrote:

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On Thu, Feb 23, 2012 at 14:39:49, Christian Riesch wrote:

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Hi,
I observed this behavior on a Texas Instruments AM1808 SoC (AM1808
experimenter's kit) running the current mainline kernel:

[snip]

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According to the AM1808 Technical Reference Manual (sections

18.2.14.1

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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

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and the warning 'resetting idled controller' disappears.

But this was not the case for me. Even after commenting out the

above lines,

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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

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message go away.

The patch below shows that changes that I did. May I please ask you to

try

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again with these changes?

I was able to reproduce the issue. I'll debug this further and get back

to you.

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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
http://www.spinics.net/lists/netdev/msg140465.html.

Cyril,
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.

Ping?

Thanks, Christian