Re: [PATCH v2 1/3] xen/arm: Add ThunderX platform support

[Ian Campbell <ian.campbell@citrix.com>]

On Tue, 2015-03-03 at 14:59 +0530, Vijay Kilari wrote:
> On Tue, Mar 3, 2015 at 2:33 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote:
> > On Tue, 2015-03-03 at 10:39 +0530, Vijay Kilari wrote:
> >> On Mon, Feb 23, 2015 at 11:21 PM, Ian Campbell <ian.campbell@citrix.com> wrote:
> >> > On Wed, 2015-02-18 at 12:38 +0000, Julien Grall wrote:
> >> >> > +    uint64_t addr, size;
> >> >
> >> > Please use paddr_t and PRIpaddr etc.
> >> >
> >> >> > +    res = map_mmio_regions(d,
> >> >> > +                           paddr_to_pfn(addr & PAGE_MASK),
> >> >> > +                           DIV_ROUND_UP(size, PAGE_SIZE),
> >> >> > +                           paddr_to_pfn(addr & PAGE_MASK));
> >> >>
> >> >> OOI, why this region is not described in the DT? Is it a PCI device?
> >> >
> >>
> >>  It is not PCI device. it is Global SerDes configuration region. It is not
> >> mentioned in DT.
> >
> > Why not? Should it be?
> 
> There is no specific driver in dom0 for this.
> It is only used by thunder pci driver in dom0 to configure serdes.

A DT is supposed to describe the hardware, so the presence or absence of
a driver in the kernel doesn't really come in to it.

> In future we plan to get rid of this. But for now we can have this
> mapping.

The problem is that removing this mapping in the future may, depending
on how it is all done, break compatibility with older kernels.

Could you describe how you plan to get rid of it please so I can see if
we need to worry about that sort of thing here?

To avoid blocking the rest of the series it might be a good idea to
factor out this specific mapping into a separate patch, then the rest
can go in, plus you can then use the commit message to explain what the
plan is etc.