[POWERPC] Fix MMIO ops to provide expected barrier behaviour

This changes the writeX family of functions to have a sync instruction
before the MMIO store rather than after, because the generally expected
behaviour is that the device receiving the MMIO store can be guaranteed
to see the effects of any preceding writes to normal memory.

To preserve ordering between writeX and readX, and to preserve ordering
between preceding stores and the readX, the readX family of functions
have had an sync added before the load.

Although writeX followed by spin_unlock is not officially guaranteed
to keep the writeX inside the spin-locked region unless an mmiowb()
is used, there are currently drivers that depend on the previous
behaviour on powerpc, which was that the mmiowb wasn't actually required.
Therefore we have a per-cpu flag that is set by writeX, cleared by
__raw_spin_lock and mmiowb, and tested by __raw_spin_unlock.  If it is
set, __raw_spin_unlock does a sync and clears it.

This changes both 32-bit and 64-bit readX/writeX.  32-bit already has a
sync in __raw_spin_unlock (since lwsync doesn't exist on 32-bit), and thus
doesn't need the per-cpu flag.

Tested on G5 (PPC970) and POWER5.

Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 25 insertions, 24 deletions

diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index fc23040d5a26..f770805f1215 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -17,15 +17,6 @@
 
         .text
 
-#ifdef CONFIG_PPC64
-#define IN_SYNC         twi     0,r5,0; isync
-#define EIEIO_32
-#define SYNC_64         sync
-#else /* CONFIG_PPC32 */
-#define IN_SYNC
-#define EIEIO_32        eieio
-#define SYNC_64
-#endif
 /*
  * Returns (address we are running at) - (address we were linked at)
  * for use before the text and data are mapped to KERNELBASE.
@@ -70,6 +61,7 @@ _GLOBAL(add_reloc_offset)
  * The *_ns versions don't do byte-swapping.
  */
 _GLOBAL(_insb)
+        sync
         cmpwi   0,r5,0
         mtctr   r5
         subi    r4,r4,1
@@ -78,7 +70,8 @@ _GLOBAL(_insb)
         eieio
         stbu    r5,1(r4)
         bdnz    00b
-        IN_SYNC
+        twi     0,r5,0
+        isync
         blr
 
 _GLOBAL(_outsb)
@@ -86,14 +79,15 @@ _GLOBAL(_outsb)
         mtctr   r5
         subi    r4,r4,1
         blelr-
+        sync
 00:     lbzu    r5,1(r4)
         stb     r5,0(r3)
-        EIEIO_32
         bdnz    00b
-        SYNC_64
+        sync
         blr
 
 _GLOBAL(_insw)
+        sync
         cmpwi   0,r5,0
         mtctr   r5
         subi    r4,r4,2
@@ -102,7 +96,8 @@ _GLOBAL(_insw)
         eieio
         sthu    r5,2(r4)
         bdnz    00b
-        IN_SYNC
+        twi     0,r5,0
+        isync
         blr
 
 _GLOBAL(_outsw)
@@ -110,14 +105,15 @@ _GLOBAL(_outsw)
         mtctr   r5
         subi    r4,r4,2
         blelr-
+        sync
 00:     lhzu    r5,2(r4)
-        EIEIO_32
         sthbrx  r5,0,r3
         bdnz    00b
-        SYNC_64
+        sync
         blr
 
 _GLOBAL(_insl)
+        sync
         cmpwi   0,r5,0
         mtctr   r5
         subi    r4,r4,4
@@ -126,7 +122,8 @@ _GLOBAL(_insl)
         eieio
         stwu    r5,4(r4)
         bdnz    00b
-        IN_SYNC
+        twi     0,r5,0
+        isync
         blr
 
 _GLOBAL(_outsl)
@@ -134,17 +131,18 @@ _GLOBAL(_outsl)
         mtctr   r5
         subi    r4,r4,4
         blelr-
+        sync
 00:     lwzu    r5,4(r4)
         stwbrx  r5,0,r3
-        EIEIO_32
         bdnz    00b
-        SYNC_64
+        sync
         blr
 
 #ifdef CONFIG_PPC32
 _GLOBAL(__ide_mm_insw)
 #endif
 _GLOBAL(_insw_ns)
+        sync
         cmpwi   0,r5,0
         mtctr   r5
         subi    r4,r4,2
@@ -153,7 +151,8 @@ _GLOBAL(_insw_ns)
         eieio
         sthu    r5,2(r4)
         bdnz    00b
-        IN_SYNC
+        twi     0,r5,0
+        isync
         blr
 
 #ifdef CONFIG_PPC32
@@ -164,17 +163,18 @@ _GLOBAL(_outsw_ns)
         mtctr   r5
         subi    r4,r4,2
         blelr-
+        sync
 00:     lhzu    r5,2(r4)
         sth     r5,0(r3)
-        EIEIO_32
         bdnz    00b
-        SYNC_64
+        sync
         blr
 
 #ifdef CONFIG_PPC32
 _GLOBAL(__ide_mm_insl)
 #endif
 _GLOBAL(_insl_ns)
+        sync
         cmpwi   0,r5,0
         mtctr   r5
         subi    r4,r4,4
@@ -183,7 +183,8 @@ _GLOBAL(_insl_ns)
         eieio
         stwu    r5,4(r4)
         bdnz    00b
-        IN_SYNC
+        twi     0,r5,0
+        isync
         blr
 
 #ifdef CONFIG_PPC32
@@ -194,10 +195,10 @@ _GLOBAL(_outsl_ns)
         mtctr   r5
         subi    r4,r4,4
         blelr-
+        sync
 00:     lwzu    r5,4(r4)
         stw     r5,0(r3)
-        EIEIO_32
         bdnz    00b
-        SYNC_64
+        sync
         blr