diff options
| author | Paul Mackerras <paulus@samba.org> | 2006-04-18 21:49:11 +1000 |
|---|---|---|
| committer | Paul Mackerras <paulus@samba.org> | 2006-04-18 21:49:11 +1000 |
| commit | f39224a8c1828bdd327539da72a53d8a13595838 (patch) | |
| tree | cc9e9139e2e7e2e36774e5c52a5311439160633c /arch/powerpc/kernel/idle_power4.S | |
| parent | 183b73ae7c9e4e19fa95d88e1778481899a65210 (diff) | |
powerpc: Use correct sequence for putting CPU into nap mode
We weren't using the recommended sequence for putting the CPU into
nap mode. When I changed the idle loop, for some reason 7447A cpus
started hanging when we put them into nap mode. Changing to the
recommended sequence fixes that.
The complexity here is that the recommended sequence is a loop that
keeps putting the cpu back into nap mode. Clearly we need some way
to break out of the loop when an interrupt (external interrupt,
decrementer, performance monitor) occurs. Here we use a bit in
the thread_info struct to indicate that we need this, and the exception
entry code notices this and arranges for the exception to return
to the value in the link register, thus breaking out of the loop.
We use a new `local_flags' field in the thread_info which we can
alter without needing to use an atomic update sequence.
The PPC970 has the same recommended sequence, so we do the same thing
there too.
This also fixes a bug in the kernel stack overflow handling code on
32-bit, since it was causing a value that we needed in a register to
get trashed.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/kernel/idle_power4.S')
| -rw-r--r-- | arch/powerpc/kernel/idle_power4.S | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/idle_power4.S b/arch/powerpc/kernel/idle_power4.S index 6dad1c02496..d85c7c938ee 100644 --- a/arch/powerpc/kernel/idle_power4.S +++ b/arch/powerpc/kernel/idle_power4.S @@ -35,12 +35,16 @@ BEGIN_FTR_SECTION DSSALL sync END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC) + clrrdi r9,r1,THREAD_SHIFT /* current thread_info */ + ld r8,TI_LOCAL_FLAGS(r9) /* set napping bit */ + ori r8,r8,_TLF_NAPPING /* so when we take an exception */ + std r8,TI_LOCAL_FLAGS(r9) /* it will return to our caller */ mfmsr r7 ori r7,r7,MSR_EE oris r7,r7,MSR_POW@h - sync +1: sync isync mtmsrd r7 isync - sync - blr + b 1b + |