ARM: v6k: select clear exclusive code seqences according to V6 variants

If CONFIG_CPU_V6 is enabled, then the kernel must support ARMv6 CPUs
which don't have the V6K extensions implemented.  Always use the
dummy store-exclusive method to ensure that the exclusive monitors are
cleared.

If CONFIG_CPU_V6 is not set, but CONFIG_CPU_32v6K is enabled, then we
have the K extensions available on all CPUs we're building support for,
so we can use the new clear-exclusive instruction.

Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Sourav Poddar <sourav.poddar@ti.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/entry-header.S

@@ -76,13 +76,13 @@
 #ifndef CONFIG_THUMB2_KERNEL
 	.macro	svc_exit, rpsr
 	msr	spsr_cxsf, \rpsr
-#if defined(CONFIG_CPU_32v6K)
-	clrex					@ clear the exclusive monitor
-	ldmia	sp, {r0 - pc}^			@ load r0 - pc, cpsr
-#elif defined (CONFIG_CPU_V6)
+#if defined(CONFIG_CPU_V6)
 	ldr	r0, [sp]
 	strex	r1, r2, [sp]			@ clear the exclusive monitor
 	ldmib	sp, {r1 - pc}^			@ load r1 - pc, cpsr
+#elif defined(CONFIG_CPU_32v6K)
+	clrex					@ clear the exclusive monitor
+	ldmia	sp, {r0 - pc}^			@ load r0 - pc, cpsr
 #else
 	ldmia	sp, {r0 - pc}^			@ load r0 - pc, cpsr
 #endif
@@ -92,10 +92,10 @@
 	ldr	r1, [sp, #\offset + S_PSR]	@ get calling cpsr
 	ldr	lr, [sp, #\offset + S_PC]!	@ get pc
 	msr	spsr_cxsf, r1			@ save in spsr_svc
-#if defined(CONFIG_CPU_32v6K)
-	clrex					@ clear the exclusive monitor
-#elif defined (CONFIG_CPU_V6)
+#if defined(CONFIG_CPU_V6)
 	strex	r1, r2, [sp]			@ clear the exclusive monitor
+#elif defined(CONFIG_CPU_32v6K)
+	clrex					@ clear the exclusive monitor
 #endif
 	.if	\fast
 	ldmdb	sp, {r1 - lr}^			@ get calling r1 - lr

arch/arm/mm/abort-ev6.S

@@ -20,11 +20,11 @@
  */
 	.align	5
 ENTRY(v6_early_abort)
-#ifdef CONFIG_CPU_32v6K
-	clrex
-#else
+#ifdef CONFIG_CPU_V6
 	sub	r1, sp, #4			@ Get unused stack location
 	strex	r0, r1, [r1]			@ Clear the exclusive monitor
+#elif defined(CONFIG_CPU_32v6K)
+	clrex
 #endif
 	mrc	p15, 0, r1, c5, c0, 0		@ get FSR
 	mrc	p15, 0, r0, c6, c0, 0		@ get FAR