On Friday 18 January 2013, Paul Mundt wrote:
> On Fri, Jan 18, 2013 at 03:55:43PM +0000, Arnd Bergmann wrote:
> > On Friday 18 January 2013, Vineet Gupta wrote:
> > > TBD: Do we need early ioremap support like openrisc
> > >
> > > Signed-off-by: Vineet Gupta <vgu...@synopsys.com>
> >
> > Can you explain why early ioremap is necessary for you?
> >
> > I wasn't aware that openrisc has it. In a lot of cases,
> > you can use fixmap as a replacement.
> >
> The two don't need to be mutually exclusive, either. sh implements early
> ioremap transparently via fixmaps for example:
>
> arch/sh/mm/ioremap.c
> arch/sh/mm/ioremap_fixed.c
Ah, right. It also seems that openrisc uses the same approach
for its early ioremap.
I usually recommend doing as few things as possible "early"
though, that's why I was asking. If it's only one or two drivers
that need an early mapping and can't be moved to a later stage
of bootup, using only hardcoded fixmaps would make it harder
to add more users, which one might consider a good thing.
Allowing ioremap to be used before memory_init() adds flexibility
but could lead to code being moved into an early stage by accident
rather than by necessity.
Arnd
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