[PATCH 03/14] ARM: v6k: remove CPU_32v6K dependencies in asm/spinlock.h

[Russell King - ARM Linux]

SMP requires at least the ARMv6K extensions to be present, so if we're
running on SMP, the WFE and SEV instructions must be available.

However, when we run on UP, the v6K extensions may not be available,
and so we don't want WFE/SEV to be in the instruction stream.  Use the
SMP alternatives infrastructure to replace these instructions with NOPs
if we build for SMP but run on UP.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 arch/arm/include/asm/spinlock.h |   37 +++++++++++++++++++++++++------------
 1 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index 17eb355..da1af52 100644
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -5,17 +5,36 @@
 #error SMP not supported on pre-ARMv6 CPUs
 #endif
 
+/*
+ * sev and wfe are ARMv6K extensions.  Uniprocessor ARMv6 may not have the K
+ * extensions, so when running on UP, we have to patch these instructions away.
+ */
+#define ALT_SMP(smp, up)					\
+	"9998:	" smp "\n"					\
+	"	.pushsection \".alt.smp.init\", \"a\"\n"	\
+	"	.long	9998b\n"				\
+	"	" up "\n"					\
+	"	.popsection\n"
+
+#ifdef CONFIG_THUMB2_KERNEL
+#define SEV		ALT_SMP("sev.w", "nop.w")
+#define WFE(cond)	ALT_SMP("wfe" cond ".w", "nop.w")
+#else
+#define SEV		ALT_SMP("sev", "nop")
+#define WFE(cond)	ALT_SMP("wfe" cond, "nop")
+#endif
+
 static inline void dsb_sev(void)
 {
 #if __LINUX_ARM_ARCH__ >= 7
 	__asm__ __volatile__ (
 		"dsb\n"
-		"sev"
+		SEV
 	);
-#elif defined(CONFIG_CPU_32v6K)
+#else
 	__asm__ __volatile__ (
 		"mcr p15, 0, %0, c7, c10, 4\n"
-		"sev"
+		SEV
 		: : "r" (0)
 	);
 #endif
@@ -46,9 +65,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
 	__asm__ __volatile__(
 "1:	ldrex	%0, [%1]\n"
 "	teq	%0, #0\n"
-#ifdef CONFIG_CPU_32v6K
-"	wfene\n"
-#endif
+	WFE("ne")
 "	strexeq	%0, %2, [%1]\n"
 "	teqeq	%0, #0\n"
 "	bne	1b"
@@ -107,9 +124,7 @@ static inline void arch_write_lock(arch_rwlock_t *rw)
 	__asm__ __volatile__(
 "1:	ldrex	%0, [%1]\n"
 "	teq	%0, #0\n"
-#ifdef CONFIG_CPU_32v6K
-"	wfene\n"
-#endif
+	WFE("ne")
 "	strexeq	%0, %2, [%1]\n"
 "	teq	%0, #0\n"
 "	bne	1b"
@@ -176,9 +191,7 @@ static inline void arch_read_lock(arch_rwlock_t *rw)
 "1:	ldrex	%0, [%2]\n"
 "	adds	%0, %0, #1\n"
 "	strexpl	%1, %0, [%2]\n"
-#ifdef CONFIG_CPU_32v6K
-"	wfemi\n"
-#endif
+	WFE("mi")
 "	rsbpls	%0, %1, #0\n"
 "	bmi	1b"
 	: "=&r" (tmp), "=&r" (tmp2)
-- 
1.6.2.5