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>
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index b3a9794..8866fd2 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -128,37 +128,36 @@
stw r12,4(r11)
#endif
b 3f
+
2: /* if from kernel, check interrupted DOZE/NAP mode and
* check for stack overflow
*/
+ lwz r9,THREAD_INFO-THREAD(r12)
+ cmplw r1,r9 /* if r1 <= current->thread_info */
+ ble- stack_ovf /* then the kernel stack overflowed */
+5:
#ifdef CONFIG_6xx
- mfspr r11,SPRN_HID0
- mtcr r11
-BEGIN_FTR_SECTION
- bt- 8,4f /* Check DOZE */
-END_FTR_SECTION_IFSET(CPU_FTR_CAN_DOZE)
-BEGIN_FTR_SECTION
- bt- 9,4f /* Check NAP */
-END_FTR_SECTION_IFSET(CPU_FTR_CAN_NAP)
+ tophys(r9,r9) /* check local flags */
+ lwz r12,TI_LOCAL_FLAGS(r9)
+ mtcrf 0x01,r12
+ bt- 31-TLF_NAPPING,4f
#endif /* CONFIG_6xx */
.globl transfer_to_handler_cont
transfer_to_handler_cont:
- lwz r11,THREAD_INFO-THREAD(r12)
- cmplw r1,r11 /* if r1 <= current->thread_info */
- ble- stack_ovf /* then the kernel stack overflowed */
3:
mflr r9
lwz r11,0(r9) /* virtual address of handler */
lwz r9,4(r9) /* where to go when done */
- FIX_SRR1(r10,r12)
mtspr SPRN_SRR0,r11
mtspr SPRN_SRR1,r10
mtlr r9
SYNC
RFI /* jump to handler, enable MMU */
-#ifdef CONFIG_6xx
-4: b power_save_6xx_restore
+#ifdef CONFIG_6xx
+4: rlwinm r12,r12,0,~_TLF_NAPPING
+ stw r12,TI_LOCAL_FLAGS(r9)
+ b power_save_6xx_restore
#endif
/*
@@ -167,10 +166,10 @@
*/
stack_ovf:
/* sometimes we use a statically-allocated stack, which is OK. */
- lis r11,_end@h
- ori r11,r11,_end@l
- cmplw r1,r11
- ble 3b /* r1 <= &_end is OK */
+ lis r12,_end@h
+ ori r12,r12,_end@l
+ cmplw r1,r12
+ ble 5b /* r1 <= &_end is OK */
SAVE_NVGPRS(r11)
addi r3,r1,STACK_FRAME_OVERHEAD
lis r1,init_thread_union@ha
