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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/xtensa/include/asm/cmpxchg.h
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@@ -13,6 +13,7 @@
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 #ifndef __ASSEMBLY__
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+#include <linux/bits.h>
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 #include <linux/stringify.h>
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 /*
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@@ -22,12 +23,29 @@
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 static inline unsigned long
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 __cmpxchg_u32(volatile int *p, int old, int new)
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 {
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-#if XCHAL_HAVE_S32C1I
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+#if XCHAL_HAVE_EXCLUSIVE
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+	unsigned long tmp, result;
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+
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 	__asm__ __volatile__(
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-			"       wsr     %2, scompare1\n"
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-			"       s32c1i  %0, %1, 0\n"
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-			: "+a" (new)
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-			: "a" (p), "a" (old)
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+			"1:     l32ex   %[result], %[addr]\n"
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+			"       bne     %[result], %[cmp], 2f\n"
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+			"       mov     %[tmp], %[new]\n"
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+			"       s32ex   %[tmp], %[addr]\n"
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+			"       getex   %[tmp]\n"
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+			"       beqz    %[tmp], 1b\n"
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+			"2:\n"
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+			: [result] "=&a" (result), [tmp] "=&a" (tmp)
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+			: [new] "a" (new), [addr] "a" (p), [cmp] "a" (old)
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+			: "memory"
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+			);
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+
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+	return result;
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+#elif XCHAL_HAVE_S32C1I
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+	__asm__ __volatile__(
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+			"       wsr     %[cmp], scompare1\n"
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+			"       s32c1i  %[new], %[mem]\n"
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+			: [new] "+a" (new), [mem] "+m" (*p)
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+			: [cmp] "a" (old)
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 			: "memory"
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 			);
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@@ -35,14 +53,14 @@
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 #else
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 	__asm__ __volatile__(
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 			"       rsil    a15, "__stringify(TOPLEVEL)"\n"
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-			"       l32i    %0, %1, 0\n"
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-			"       bne     %0, %2, 1f\n"
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-			"       s32i    %3, %1, 0\n"
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+			"       l32i    %[old], %[mem]\n"
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+			"       bne     %[old], %[cmp], 1f\n"
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+			"       s32i    %[new], %[mem]\n"
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 			"1:\n"
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 			"       wsr     a15, ps\n"
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 			"       rsync\n"
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-			: "=&a" (old)
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-			: "a" (p), "a" (old), "r" (new)
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+			: [old] "=&a" (old), [mem] "+m" (*p)
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+			: [cmp] "a" (old), [new] "r" (new)
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 			: "a15", "memory");
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 	return old;
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 #endif
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@@ -107,16 +125,32 @@
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 static inline unsigned long xchg_u32(volatile int * m, unsigned long val)
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 {
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-#if XCHAL_HAVE_S32C1I
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+#if XCHAL_HAVE_EXCLUSIVE
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+	unsigned long tmp, result;
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+
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+	__asm__ __volatile__(
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+			"1:     l32ex   %[result], %[addr]\n"
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+			"       mov     %[tmp], %[val]\n"
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+			"       s32ex   %[tmp], %[addr]\n"
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+			"       getex   %[tmp]\n"
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+			"       beqz    %[tmp], 1b\n"
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+			: [result] "=&a" (result), [tmp] "=&a" (tmp)
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+			: [val] "a" (val), [addr] "a" (m)
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+			: "memory"
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+			);
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+
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+	return result;
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+#elif XCHAL_HAVE_S32C1I
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 	unsigned long tmp, result;
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 	__asm__ __volatile__(
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-			"1:     l32i    %1, %2, 0\n"
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-			"       mov     %0, %3\n"
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-			"       wsr     %1, scompare1\n"
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-			"       s32c1i  %0, %2, 0\n"
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-			"       bne     %0, %1, 1b\n"
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-			: "=&a" (result), "=&a" (tmp)
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-			: "a" (m), "a" (val)
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+			"1:     l32i    %[tmp], %[mem]\n"
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+			"       mov     %[result], %[val]\n"
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+			"       wsr     %[tmp], scompare1\n"
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+			"       s32c1i  %[result], %[mem]\n"
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+			"       bne     %[result], %[tmp], 1b\n"
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+			: [result] "=&a" (result), [tmp] "=&a" (tmp),
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+			  [mem] "+m" (*m)
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+			: [val] "a" (val)
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 			: "memory"
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 			);
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 	return result;
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@@ -124,12 +158,12 @@
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 	unsigned long tmp;
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 	__asm__ __volatile__(
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 			"       rsil    a15, "__stringify(TOPLEVEL)"\n"
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-			"       l32i    %0, %1, 0\n"
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-			"       s32i    %2, %1, 0\n"
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+			"       l32i    %[tmp], %[mem]\n"
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+			"       s32i    %[val], %[mem]\n"
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 			"       wsr     a15, ps\n"
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 			"       rsync\n"
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-			: "=&a" (tmp)
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-			: "a" (m), "a" (val)
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+			: [tmp] "=&a" (tmp), [mem] "+m" (*m)
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+			: [val] "a" (val)
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 			: "a15", "memory");
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 	return tmp;
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 #endif
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@@ -137,6 +171,28 @@
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 #define xchg(ptr,x) \
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 	((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
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+
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+static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
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+{
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+	int off = (unsigned long)ptr % sizeof(u32);
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+	volatile u32 *p = ptr - off;
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+#ifdef __BIG_ENDIAN
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+	int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
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+#else
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+	int bitoff = off * BITS_PER_BYTE;
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+#endif
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+	u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
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+	u32 oldv, newv;
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+	u32 ret;
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+
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+	do {
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+		oldv = READ_ONCE(*p);
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+		ret = (oldv & bitmask) >> bitoff;
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+		newv = (oldv & ~bitmask) | (x << bitoff);
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+	} while (__cmpxchg_u32(p, oldv, newv) != oldv);
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+
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+	return ret;
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+}
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 /*
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  * This only works if the compiler isn't horribly bad at optimizing.
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@@ -150,11 +206,16 @@
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 __xchg(unsigned long x, volatile void * ptr, int size)
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 {
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 	switch (size) {
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-		case 4:
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-			return xchg_u32(ptr, x);
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+	case 1:
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+		return xchg_small(ptr, x, 1);
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+	case 2:
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+		return xchg_small(ptr, x, 2);
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+	case 4:
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+		return xchg_u32(ptr, x);
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+	default:
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+		__xchg_called_with_bad_pointer();
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+		return x;
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 	}
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-	__xchg_called_with_bad_pointer();
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-	return x;
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 }
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 #endif /* __ASSEMBLY__ */