parisc: Use ldcw instruction for SMP spinlock release barrier

There are only a couple of instructions that can function as a memory
barrier on parisc.  Currently, we use the sync instruction as a memory
barrier when releasing a spinlock.  However, the ldcw instruction is a
better barrier when we have a handy memory location since it operates in
the cache on coherent machines.

This patch updates the spinlock release code to use ldcw.  I also
changed the "stw,ma" instructions to "stw" instructions as it is not an
adequate barrier.
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/include/asm/spinlock.h

@@ -37,7 +37,11 @@ static inline void arch_spin_unlock(arch_spinlock_t *x)
 	volatile unsigned int *a;
 
 	a = __ldcw_align(x);
+#ifdef CONFIG_SMP
+	(void) __ldcw(a);
+#else
 	mb();
+#endif
 	*a = 1;
 }
 

arch/parisc/kernel/entry.S

@@ -471,8 +471,9 @@
 	nop
 	LDREG		0(\ptp),\pte
 	bb,<,n		\pte,_PAGE_PRESENT_BIT,3f
+	LDCW		0(\tmp),\tmp1
 	b		\fault
-	stw,ma		\spc,0(\tmp)
+	stw		\spc,0(\tmp)
 99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
 #endif
 2:	LDREG		0(\ptp),\pte
@@ -481,20 +482,22 @@
 	.endm
 
 	/* Release pa_tlb_lock lock without reloading lock address. */
-	.macro		tlb_unlock0	spc,tmp
+	.macro		tlb_unlock0	spc,tmp,tmp1
 #ifdef CONFIG_SMP
 98:	or,COND(=)	%r0,\spc,%r0
-	stw,ma		\spc,0(\tmp)
+	LDCW		0(\tmp),\tmp1
+	or,COND(=)	%r0,\spc,%r0
+	stw		\spc,0(\tmp)
 99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
 #endif
 	.endm
 
 	/* Release pa_tlb_lock lock. */
-	.macro		tlb_unlock1	spc,tmp
+	.macro		tlb_unlock1	spc,tmp,tmp1
 #ifdef CONFIG_SMP
 98:	load_pa_tlb_lock \tmp
 99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
-	tlb_unlock0	\spc,\tmp
+	tlb_unlock0	\spc,\tmp,\tmp1
 #endif
 	.endm
 
@@ -1177,7 +1180,7 @@ dtlb_miss_20w:
 	
 	idtlbt          pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1203,7 +1206,7 @@ nadtlb_miss_20w:
 
 	idtlbt          pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1237,7 +1240,7 @@ dtlb_miss_11:
 
 	mtsp		t1, %sr1	/* Restore sr1 */
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1270,7 +1273,7 @@ nadtlb_miss_11:
 
 	mtsp		t1, %sr1	/* Restore sr1 */
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1299,7 +1302,7 @@ dtlb_miss_20:
 
 	idtlbt          pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1327,7 +1330,7 @@ nadtlb_miss_20:
 	
 	idtlbt		pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1434,7 +1437,7 @@ itlb_miss_20w:
 	
 	iitlbt          pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1458,7 +1461,7 @@ naitlb_miss_20w:
 
 	iitlbt          pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1492,7 +1495,7 @@ itlb_miss_11:
 
 	mtsp		t1, %sr1	/* Restore sr1 */
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1516,7 +1519,7 @@ naitlb_miss_11:
 
 	mtsp		t1, %sr1	/* Restore sr1 */
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1546,7 +1549,7 @@ itlb_miss_20:
 
 	iitlbt          pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1566,7 +1569,7 @@ naitlb_miss_20:
 
 	iitlbt          pte,prot
 
-	tlb_unlock1	spc,t0
+	tlb_unlock1	spc,t0,t1
 	rfir
 	nop
 
@@ -1596,7 +1599,7 @@ dbit_trap_20w:
 		
 	idtlbt          pte,prot
 
-	tlb_unlock0	spc,t0
+	tlb_unlock0	spc,t0,t1
 	rfir
 	nop
 #else
@@ -1622,7 +1625,7 @@ dbit_trap_11:
 
 	mtsp            t1, %sr1     /* Restore sr1 */
 
-	tlb_unlock0	spc,t0
+	tlb_unlock0	spc,t0,t1
 	rfir
 	nop
 
@@ -1642,7 +1645,7 @@ dbit_trap_20:
 	
 	idtlbt		pte,prot
 
-	tlb_unlock0	spc,t0
+	tlb_unlock0	spc,t0,t1
 	rfir
 	nop
 #endif

arch/parisc/kernel/syscall.S

@@ -640,7 +640,9 @@ cas_action:
 	sub,<>	%r28, %r25, %r0
 2:	stw	%r24, 0(%r26)
 	/* Free lock */
-	sync
+#ifdef CONFIG_SMP
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
+#endif
 	stw	%r20, 0(%sr2,%r20)
 #if ENABLE_LWS_DEBUG
 	/* Clear thread register indicator */
@@ -655,7 +657,9 @@ cas_action:
 3:		
 	/* Error occurred on load or store */
 	/* Free lock */
-	sync
+#ifdef CONFIG_SMP
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
+#endif
 	stw	%r20, 0(%sr2,%r20)
 #if ENABLE_LWS_DEBUG
 	stw	%r0, 4(%sr2,%r20)
@@ -857,7 +861,9 @@ cas2_action:
 
 cas2_end:
 	/* Free lock */
-	sync
+#ifdef CONFIG_SMP
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
+#endif
 	stw	%r20, 0(%sr2,%r20)
 	/* Enable interrupts */
 	ssm	PSW_SM_I, %r0
@@ -868,7 +874,9 @@ cas2_end:
 22:
 	/* Error occurred on load or store */
 	/* Free lock */
-	sync
+#ifdef CONFIG_SMP
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
+#endif
 	stw	%r20, 0(%sr2,%r20)
 	ssm	PSW_SM_I, %r0
 	ldo	1(%r0),%r28