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SubjectRe: [PATCH v4 2/5] arm: add new asm macro update_sctlr
On Mon, Feb 03, 2014 at 10:34:15AM +0000, Will Deacon wrote:
> On Thu, Jan 30, 2014 at 01:12:47PM +0000, Leif Lindholm wrote:
> > Oh, that's neat - thanks!
> >
> > Well, given that, I can think of two less horrible options:
> > 1)
> > .macro update_sctlr, tmp:req, set=, clear=
> > mrc p15, 0, \tmp, c1, c0, 0
> > .ifnc \set,
> > orr \tmp, \set
> > .endif
> > .ifnc \clear,
> > mvn \clear, \clear
> > and \tmp, \tmp, \clear
>
> Can't you use bic here?

Yeah.

> > .endif
> > mcr p15, 0, \tmp, c1, c0, 0
> > .endm
> >
> > With the two call sites in uefi_phys.S as:
> >
> > ldr r5, =(CR_M)
> > update_sctlr r12, , r5
> > and
> > ldr r4, =(CR_I | CR_C | CR_M)
> > update_sctlr r12, r4
>
> These ldr= could be movs, right?

The first one could.
The second one could be movw on armv7+.

> If so, I definitely prefer this to putting an ldr = into the macro itself
> (option 2).

And your preference between 1) and 2) is?

/
Leif


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