Subject: Re: [PATCH] powerpc: enable access to HT Host-Bridge on Maple

From: Benjamin Herrenschmidt <[email-masked]>
Date: Fri, 08 Jul 2011 08:48:53 +1000

On Fri, 2011-07-01 at 18:44 +0200, Segher Boessenkool wrote:
> > CPC925/CPC945 use special window to access host bridge  
> > functionality of
> > u3-ht. Provide a way to access this device.
> 
> Why?  Is anything going to use it?
> 
> > +static int u3_ht_root_read_config(struct pci_controller *hose, u8  
> > offset,
> > +				  int len, u32 *val)
> > +{
> > +	volatile void __iomem *addr;
> > +
> > +	addr = hose->cfg_addr;
> > +	addr += ((offset & ~3) << 2) + (4 - len - (offset & 3));
> 
> This will only work for len 1,2,4 with offset a multiple of len, is that
> guaranteed here?

I think the upper layer does. Dbl check tho.

> >  	hose->cfg_data = ioremap(0xf2000000, 0x02000000);
> > +	hose->cfg_addr = ioremap(0xf8070000, 0x1000);
> 
> Eww.  You could just make a global instead of abusing existing fields,
> there can be only one CPC9x5 in a system anyway.

Nah, that's fine, we abuse it that way regulary :-)

Cheers,
Ben.