[U-Boot] [PATCH] at91: Add support for taskit AT91SAM9G20 boards.

[Markus Hubig <mhubig@imko.de>]

On Thu, Aug 02, 2012 at 03:28:30PM +0200, Markus Hubig wrote:
> On Wed, Aug 01, 2012 at 10:21:04PM +0200, Andreas Bie?mann wrote:
> > On 01.08.12 21:28, Markus Hubig wrote:
> > > On Wed, Aug 01, 2012 at 11:58:22AM +0200, Andreas Bie?mann wrote:
> > >>> +	/* Need to reset PHY -> 500ms reset */
> > >>> +	writel(AT91_RSTC_KEY | AT91_RSTC_MR_ERSTL(13) |
> > >>> +		AT91_RSTC_MR_URSTEN, &rstc->mr);
> > >>
> > >> Hmm ... is it OK to generate the user reset here? I know this is the
> > >> same in at least at91sam9263ek, can you please check if we should
> > >> instead delete that bit in MR?
> > > 
> > > MR? Sorry I don't get this one. Please explain a bit ...
> > 
> > I talked about URSTEN bit in RSTC_MR (Reset Controller Mode Register;
> > p99 in at91sam9g20 datasheet). The URSTEN bit set to 1 means disable low
> > level detection on NRST pin. Which in fact disables external reset with
> > the reset key. One have to check if this is true or maybe I'm wrong here.
> 
> Hmm ok I'll investigate this a bit further ...

OK I looked this up in the at91sam9g20 datasheet, but as fahr as I understand
it, setting AT91_RSTC_MR_URSTEN enables the *detection* of a low level on NRST
to trigger USER RESET, while in order to perform the PHY Reset, NRST just hast
to get low. To get NRST low, one has to set EXTRST in RSTC_CR.

So to perform a PHY Reset, the correct code should be:

| /* Reset PHY for 500ms */
| writel(AT91_RSTC_KEY | AT91_RSTC_MR_ERSTL(13)
|	& ~AT91_RSTC_MR_URSTEN, &rstc->mr);
| writel(AT91_RSTC_KEY | AT91_RSTC_CR_EXTRST, &rstc->cr);

I tested it with my PortuxG20 and Network is still working!

Unfortunatlie the Portux has no reset button, but I think for all at91sam9g20
boards with a reset button the AT91_RSTC_MR_URSTEN has to be high by default,
so somewhere in arch/arm/cpu/arm926ejs/at91/ there has to be some code like
this:

|#ifdef CONFIG_AT91_RESET_BUTTON
|struct at91_rstc *rstc = (struct at91_rstc *)ATMEL_BASE_RSTC;
|writel(AT91_RSTC_KEY | AT91_RSTC_MR_URSTEN, &rstc->mr);
|#endif

Cheers, Markus