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Make cpu_get_real_ticks use mfspr

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PowerPC CPUs have had two ways to read the time base for quite some time now.
They provide it using the mfspr instruction or - if a special bit is set in
that opcode - using mftb. For timekeeping we're currently using mftb.

While trying to get Qemu up and running on an e500v2 system, I stumbled over
the CPU not supporting mftbu. It just throws an illegal instruction trap.

So let's read the SPR values instead. All PPC CPUs should support them anyways.

I tested this patch on an e500v2 system where it makes qemu work and on my 970MP
system with 32-bit user space where everything still works with this patch
applied.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: malc <av1474@comtv.ru>
This commit is contained in:
Alexander Graf 2010-04-03 11:37:26 +02:00 committed by malc
parent 93c5a32f89
commit 4a9590f32e
1 changed files with 3 additions and 3 deletions
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6
qemu-timer.h
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@ -98,9 +98,9 @@ static inline int64_t cpu_get_real_ticks(void)
#else #else
/* http://ozlabs.org/pipermail/linuxppc-dev/1999-October/003889.html */ /* http://ozlabs.org/pipermail/linuxppc-dev/1999-October/003889.html */
unsigned long junk; unsigned long junk;
__asm__ __volatile__ ("mftbu %1\n\t" __asm__ __volatile__ ("mfspr %1,269\n\t" /* mftbu */
"mftb %L0\n\t" "mfspr %L0,268\n\t" /* mftb */
"mftbu %0\n\t" "mfspr %0,269\n\t" /* mftbu */
"cmpw %0,%1\n\t" "cmpw %0,%1\n\t"
"bne $-16" "bne $-16"
: "=r" (retval), "=r" (junk)); : "=r" (retval), "=r" (junk));