[RFC PATCH v3 05/12] powerpc: reverse the soft_enable logic

[Madhavan Srinivasan <maddy@linux.vnet.ibm.com>]

"paca->soft_enabled" is used as a flag to mask some of interrupts.
Currently supported flags values and their details:

soft_enabled    MSR[EE]

0               0       Disabled (PMI and HMI not masked)
1               1       Enabled

"paca->soft_enabled" is initialized to 1 to make the interripts as
enabled. arch_local_irq_disable() will toggle the value when interrupts
needs to disbled. At this point, the interrupts are not actually disabled,
instead, interrupt vector has code to check for the flag and mask it when it occurs.
By "mask it", it update interrupt paca->irq_happened and return.
arch_local_irq_restore() is called to re-enable interrupts, which checks and
replays interrupts if any occured.

Now, as mentioned, current logic doesnot mask "performance monitoring interrupts"
and PMIs are implemented as NMI. But this patchset depends on local_irq_*
for a successful local_* update. Meaning, mask all possible interrupts during
local_* update and replay them after the update.

So the idea here is to reserve the "paca->soft_enabled" logic. New values and
details:

soft_enabled    MSR[EE]

1               0       Disabled  (PMI and HMI not masked)
0               1       Enabled

Reason for the this change is to create foundation for a third flag value "2"
for "soft_enabled" to add support to mask PMIs.

Foundation patch to support checking of new flag value for "paca->soft_enabled".
Modify the condition checking for the "soft_enabled".

Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/hw_irq.h | 4 ++--
 arch/powerpc/kernel/entry_64.S    | 5 ++---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index a7564b8a4831..c19169ac1fbb 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -30,8 +30,8 @@
 /*
  * flags for paca->soft_enabled
  */
-#define IRQ_DISABLE_MASK_NONE		1
-#define IRQ_DISABLE_MASK_LINUX		0
+#define IRQ_DISABLE_MASK_NONE		0
+#define IRQ_DISABLE_MASK_LINUX		1
 
 #endif /* CONFIG_PPC64 */
 
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 3078de64824b..b50d79e5bfbc 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -131,8 +131,7 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR)
 	 */
 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_BUG)
 	lbz	r10,PACASOFTIRQEN(r13)
-	xori	r10,r10,IRQ_DISABLE_MASK_NONE
-1:	tdnei	r10,0
+1:	tdnei	r10,IRQ_DISABLE_MASK_NONE
 	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
 #endif
 
@@ -1012,7 +1011,7 @@ _GLOBAL(enter_rtas)
 	 * check it with the asm equivalent of WARN_ON
 	 */
 	lbz	r0,PACASOFTIRQEN(r13)
-1:	tdnei	r0,IRQ_DISABLE_MASK_LINUX
+1:	tdeqi	r0,IRQ_DISABLE_MASK_NONE
 	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
 #endif
 	
-- 
2.7.4