1 files changed, 48 insertions, 0 deletions
diff --git a/firmware/include/asm/div64.h b/firmware/include/asm/div64.h
new file mode 100644
index 0000000..3682616
--- /dev/null
+++ b/firmware/include/asm/div64.h
@@ -0,0 +1,48 @@
+#ifndef __ASM_ARM_DIV64
+#define __ASM_ARM_DIV64
+
+#include <asm/system.h>
+
+/*
+ * The semantics of do_div() are:
+ *
+ * uint32_t do_div(uint64_t *n, uint32_t base)
+ * {
+ * 	uint32_t remainder = *n % base;
+ * 	*n = *n / base;
+ * 	return remainder;
+ * }
+ *
+ * In other words, a 64-bit dividend with a 32-bit divisor producing
+ * a 64-bit result and a 32-bit remainder.  To accomplish this optimally
+ * we call a special __do_div64 helper with completely non standard
+ * calling convention for arguments and results (beware).
+ */
+
+#ifdef __ARMEB__
+#define __xh "r0"
+#define __xl "r1"
+#else
+#define __xl "r0"
+#define __xh "r1"
+#endif
+
+#define do_div(n,base)						\
+({								\
+	register unsigned int __base      asm("r4") = base;	\
+	register unsigned long long __n   asm("r0") = n;	\
+	register unsigned long long __res asm("r2");		\
+	register unsigned int __rem       asm(__xh);		\
+	asm(	__asmeq("%0", __xh)				\
+		__asmeq("%1", "r2")				\
+		__asmeq("%2", "r0")				\
+		__asmeq("%3", "r4")				\
+		"bl	__do_div64"				\
+		: "=r" (__rem), "=r" (__res)			\
+		: "r" (__n), "r" (__base)			\
+		: "ip", "lr", "cc");				\
+	n = __res;						\
+	__rem;							\
+})
+
+#endif