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microblaze: Improve checking mechanism for MSR instruction 

It is more safe to use clear instead of msrset.
We save some instructions too.

Signed-off-by: Michal Simek <monstr@monstr.eu>
This commit is contained in:
Michal Simek 2009-08-31 16:24:56 +02:00
parent 2622434ee0
commit 9002062ff5
1 changed files with 5 additions and 8 deletions
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13
arch/microblaze/kernel/head.S
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@ -54,19 +54,16 @@ ENTRY(_start)
mfs r1, rmsr
andi r1, r1, ~2
mts rmsr, r1
/*
* Here is checking mechanism which check if Microblaze has msr instructions
* We load msr and compare it with previous r1 value - if is the same,
* msr instructions works if not - cpu don't have them.
*/
or r8, r0, r0 /* 0 - I have msr instr, 1 - I don't have */
or r12, r0, r0
msrset r12, 0 /* set nothing - just read msr for test */
cmpu r12, r12, r1
beqi r12, 1f
ori r8, r0, 1 /* I don't have msr */
1:
/* r8=0 - I have msr instr, 1 - I don't have them */
rsubi r0, r0, 1 /* set the carry bit */
msrclr r0, 0x4 /* try to clear it */
/* read the carry bit, r8 will be '0' if msrclr exists */
addik r8, r0, 0
/* r7 may point to an FDT, or there may be one linked in.
if it's in r7, we've got to save it away ASAP.