Re: [XenPPC] [xenppc-unstable] [XEN][POWERPC] SCOM access is fully known and working

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

On Sep 21, 2006, at 12:21 PM, Segher Boessenkool wrote:

> > +    /* these give iface errors because the address is ambiguous  
> > after
> > +     * the above bit dropping */
> > +    BUG_ON(addr == 0x8000);
> Anything with the high bit set isn't available via SCOMC/SCOMD,
> only via the external interfaces.
Thanks for clarifying that, will fix.

> > +        /* WARNING! older 970s (pre FX) shift the bits right 1  
> > position */
> They also don't have the exact same stuff at the exact same
> registers -- SCOM is very CPU-specific, check every one you
> want to use.  That is, if you do the fix for the shifted bits,
> if not, don't bother ;-)
Just a note-to-self until I get my hands on the early docs.


> > +        if (c.bits.iface_error)
> > +            udelay(10);
> Why the udelay()?
This is interesting,  The docs say that you should "retry" on an  
iface error.
When accessing the 0x8000 address above I get an iface error, then an  
immediate retry gives an addr|iface error.
If I wait 10us (a number I made up) before the retry I get only iface  
consistently.
I'm waiting to hear back on the expected behavior, I will adjust at  
that point.
> > +/* SCOMC addresses are 16bit but we are given 24 bits in the
> > + * books. The low oerder 8 bits are some kinda parity thin and  
> > should
> > + * be ignored */
> The low bit is the odd parity of the other 23 bits; everything
> accessible via SCOMC/SCOMD has bits 16..22 zero.
Interesting thanks for the heads up.
> All these comments are pretty minor, congratz on finally having
> it working Jimi :-)
yeah.. now for the payoff

-JX

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