From f39224a8c1828bdd327539da72a53d8a13595838 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Tue, 18 Apr 2006 21:49:11 +1000 Subject: 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 --- arch/powerpc/kernel/idle_power4.S | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'arch/powerpc/kernel/idle_power4.S') diff --git a/arch/powerpc/kernel/idle_power4.S b/arch/powerpc/kernel/idle_power4.S index 6dad1c02496e..d85c7c938eed 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 + -- cgit v1.2.2