[PATCH v11 04/14] arm64: support WFET in smp_cond_load_relaxed_timeout()

[Ankur Arora <ankur.a.arora@oracle.com>]

To handle WFET use __cmpwait_timeout() similarly to __cmpwait(). These
call out to the respective __cmpwait_case_timeout_##sz(),
__cmpwait_case_##sz() functions.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 arch/arm64/include/asm/barrier.h |  8 +++--
 arch/arm64/include/asm/cmpxchg.h | 62 +++++++++++++++++++++++++-------
 2 files changed, 55 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 6190e178db51..fbd71cd4ef4e 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -224,8 +224,8 @@ do {									\
 extern bool arch_timer_evtstrm_available(void);
 
 /*
- * In the common case, cpu_poll_relax() sits waiting in __cmpwait_relaxed()
- * for the ptr value to change.
+ * In the common case, cpu_poll_relax() sits waiting in __cmpwait_relaxed()/
+ * __cmpwait_relaxed_timeout() for the ptr value to change.
  *
  * Since this period is reasonably long, choose SMP_TIMEOUT_POLL_COUNT
  * to be 1, so smp_cond_load_{relaxed,acquire}_timeout() does a
@@ -234,7 +234,9 @@ extern bool arch_timer_evtstrm_available(void);
 #define SMP_TIMEOUT_POLL_COUNT	1
 
 #define cpu_poll_relax(ptr, val, timeout_ns) do {			\
-	if (arch_timer_evtstrm_available())				\
+	if (alternative_has_cap_unlikely(ARM64_HAS_WFXT))		\
+		__cmpwait_relaxed_timeout(ptr, val, timeout_ns);	\
+	else if (arch_timer_evtstrm_available())			\
 		__cmpwait_relaxed(ptr, val);				\
 	else								\
 		cpu_relax();						\
diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
index 6cf3cd6873f5..9e4cdc9e41d1 100644
--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -12,6 +12,7 @@
 
 #include <asm/barrier.h>
 #include <asm/lse.h>
+#include <asm/delay-const.h>
 
 /*
  * We need separate acquire parameters for ll/sc and lse, since the full
@@ -212,7 +213,8 @@ __CMPXCHG_GEN(_mb)
 
 #define __CMPWAIT_CASE(w, sfx, sz)					\
 static inline void __cmpwait_case_##sz(volatile void *ptr,		\
-				       unsigned long val)		\
+				       unsigned long val,		\
+				       u64 __maybe_unused timeout_ns)	\
 {									\
 	unsigned long tmp;						\
 									\
@@ -235,20 +237,52 @@ __CMPWAIT_CASE( ,  , 64);
 
 #undef __CMPWAIT_CASE
 
-#define __CMPWAIT_GEN(sfx)						\
-static __always_inline void __cmpwait##sfx(volatile void *ptr,		\
-				  unsigned long val,			\
-				  int size)				\
+#define __CMPWAIT_TIMEOUT_CASE(w, sfx, sz)				\
+static inline void __cmpwait_case_timeout_##sz(volatile void *ptr,	\
+					       unsigned long val,	\
+					       u64 timeout_ns)		\
+{									\
+	unsigned long tmp;						\
+	u64 ecycles = __delay_cycles() +				\
+			NSECS_TO_CYCLES(timeout_ns);			\
+	asm volatile(							\
+	"	sevl\n"							\
+	"	wfe\n"							\
+	"	ldxr" #sfx "\t%" #w "[tmp], %[v]\n"			\
+	"	eor	%" #w "[tmp], %" #w "[tmp], %" #w "[val]\n"	\
+	"	cbnz	%" #w "[tmp], 2f\n"				\
+	"	msr s0_3_c1_c0_0, %[ecycles]\n"				\
+	"2:"								\
+	: [tmp] "=&r" (tmp), [v] "+Q" (*(u##sz *)ptr)			\
+	: [val] "r" (val), [ecycles] "r" (ecycles));			\
+}
+
+__CMPWAIT_TIMEOUT_CASE(w, b, 8);
+__CMPWAIT_TIMEOUT_CASE(w, h, 16);
+__CMPWAIT_TIMEOUT_CASE(w,  , 32);
+__CMPWAIT_TIMEOUT_CASE( ,  , 64);
+
+#undef __CMPWAIT_TIMEOUT_CASE
+
+#define __CMPWAIT_GEN(timeout, sfx)					\
+static __always_inline void __cmpwait##timeout##sfx(volatile void *ptr,	\
+						    unsigned long val,	\
+						    u64 timeout_ns,	\
+						    int size)		\
 {									\
 	switch (size) {							\
 	case 1:								\
-		return __cmpwait_case##sfx##_8(ptr, (u8)val);		\
+		return __cmpwait_case##timeout##sfx##_8(ptr, (u8)val,	\
+							timeout_ns);	\
 	case 2:								\
-		return __cmpwait_case##sfx##_16(ptr, (u16)val);		\
+		return __cmpwait_case##timeout##sfx##_16(ptr, (u16)val,	\
+							 timeout_ns);	\
 	case 4:								\
-		return __cmpwait_case##sfx##_32(ptr, val);		\
+		return __cmpwait_case##timeout##sfx##_32(ptr, val,	\
+							 timeout_ns);	\
 	case 8:								\
-		return __cmpwait_case##sfx##_64(ptr, val);		\
+		return __cmpwait_case##timeout##sfx##_64(ptr, val,	\
+							 timeout_ns);	\
 	default:							\
 		BUILD_BUG();						\
 	}								\
@@ -256,11 +290,15 @@ static __always_inline void __cmpwait##sfx(volatile void *ptr,		\
 	unreachable();							\
 }
 
-__CMPWAIT_GEN()
+__CMPWAIT_GEN(        , )
+__CMPWAIT_GEN(_timeout, )
 
 #undef __CMPWAIT_GEN
 
-#define __cmpwait_relaxed(ptr, val) \
-	__cmpwait((ptr), (unsigned long)(val), sizeof(*(ptr)))
+#define __cmpwait_relaxed_timeout(ptr, val, timeout_ns)			\
+	__cmpwait_timeout((ptr), (unsigned long)(val), timeout_ns, sizeof(*(ptr)))
+
+#define __cmpwait_relaxed(ptr, val)					\
+	__cmpwait((ptr), (unsigned long)(val), 0, sizeof(*(ptr)))
 
 #endif	/* __ASM_CMPXCHG_H */
-- 
2.31.1