[PATCH V2] riscv: Implement smp_cond_load8/16() with Zawrs

[guoren@kernel.org]

From: Guo Ren <guoren@linux.alibaba.com>

RISC-V code uses the queued spinlock implementation, which calls
the macros smp_cond_load_acquire for one byte. So, complement the
implementation of byte and halfword versions.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Andrew Jones <ajones@ventanamicro.com>
---
Changes in V2:
 - Fixup mask typo (0xf -> 0xff, 0xff -> 0xffff) by Andrew.
---
 arch/riscv/include/asm/cmpxchg.h | 38 +++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index 4cadc56220fe..aa4410beb065 100644
--- a/arch/riscv/include/asm/cmpxchg.h
+++ b/arch/riscv/include/asm/cmpxchg.h
@@ -365,16 +365,48 @@ static __always_inline void __cmpwait(volatile void *ptr,
 {
 	unsigned long tmp;
 
+	u32 *__ptr32b;
+	ulong __s, __val, __mask;
+
 	asm goto(ALTERNATIVE("j %l[no_zawrs]", "nop",
 			     0, RISCV_ISA_EXT_ZAWRS, 1)
 		 : : : : no_zawrs);
 
 	switch (size) {
 	case 1:
-		fallthrough;
+		__ptr32b = (u32 *)((ulong)(ptr) & ~0x3);
+		__s = ((ulong)(ptr) & 0x3) * BITS_PER_BYTE;
+		__val = val << __s;
+		__mask = 0xff << __s;
+
+		asm volatile(
+		"	lr.w	%0, %1\n"
+		"	and	%0, %0, %3\n"
+		"	xor	%0, %0, %2\n"
+		"	bnez	%0, 1f\n"
+			ZAWRS_WRS_NTO "\n"
+		"1:"
+		: "=&r" (tmp), "+A" (*(__ptr32b))
+		: "r" (__val), "r" (__mask)
+		: "memory");
+		break;
 	case 2:
-		/* RISC-V doesn't have lr instructions on byte and half-word. */
-		goto no_zawrs;
+		__ptr32b = (u32 *)((ulong)(ptr) & ~0x3);
+		__s = ((ulong)(ptr) & 0x2) * BITS_PER_BYTE;
+		__val = val << __s;
+		__mask = 0xffff << __s;
+
+		asm volatile(
+		"	lr.w	%0, %1\n"
+		"	and	%0, %0, %3\n"
+		"	xor	%0, %0, %2\n"
+		"	bnez	%0, 1f\n"
+			ZAWRS_WRS_NTO "\n"
+		"1:"
+		: "=&r" (tmp), "+A" (*(__ptr32b))
+		: "r" (__val), "r" (__mask)
+		: "memory");
+		break;
 	case 4:
 		asm volatile(
 		"	lr.w	%0, %1\n"
-- 
2.40.1