VisionFive2 Linux kernel

StarFive Tech Linux Kernel for VisionFive (JH7110) boards (mirror)

More than 9999 Commits   32 Branches   54 Tags
author: Linus Torvalds <torvalds@linux-foundation.org> 2016-05-28 16:15:25 -0700 committer: Linus Torvalds <torvalds@linux-foundation.org> 2016-05-28 16:15:25 -0700 commit: 7e0fb73c52c4037b4d5ef9ff56c7296a3151bd92 parent: 4e8440b3b6b801953b2e53c55491cf98fc8f6c01
Commit Summary:
Merge branch 'hash' of git://ftp.sciencehorizons.net/linux
Diffstat:
1 file changed, 47 insertions, 0 deletions
diff --git a/arch/h8300/include/asm/hash.h b/arch/h8300/include/asm/hash.h
new file mode 100644
index 000000000000..04cfbd2bd850
--- /dev/null
+++ b/arch/h8300/include/asm/hash.h
@@ -0,0 +1,53 @@
+#ifndef _ASM_HASH_H
+#define _ASM_HASH_H
+
+/*
+ * The later H8SX models have a 32x32-bit multiply, but the H8/300H
+ * and H8S have only 16x16->32.  Since it's tolerably compact, this is
+ * basically an inlined version of the __mulsi3 code.  Since the inputs
+ * are not expected to be small, it's also simplfied by skipping the
+ * early-out checks.
+ *
+ * (Since neither CPU has any multi-bit shift instructions, a
+ * shift-and-add version is a non-starter.)
+ *
+ * TODO: come up with an arch-specific version of the hashing in fs/namei.c,
+ * since that is heavily dependent on rotates.  Which, as mentioned, suck
+ * horribly on H8.
+ */
+
+#if defined(CONFIG_CPU_H300H) || defined(CONFIG_CPU_H8S)
+
+#define HAVE_ARCH__HASH_32 1
+
+/*
+ * Multiply by k = 0x61C88647.  Fitting this into three registers requires
+ * one extra instruction, but reducing register pressure will probably
+ * make that back and then some.
+ *
+ * GCC asm note: %e1 is the high half of operand %1, while %f1 is the
+ * low half.  So if %1 is er4, then %e1 is e4 and %f1 is r4.
+ *
+ * This has been designed to modify x in place, since that's the most
+ * common usage, but preserve k, since hash_64() makes two calls in
+ * quick succession.
+ */
+static inline u32 __attribute_const__ __hash_32(u32 x)
+{
+	u32 temp;
+
+	asm(   "mov.w	%e1,%f0"
+	"\n	mulxu.w	%f2,%0"		/* klow * xhigh */
+	"\n	mov.w	%f0,%e1"	/* The extra instruction */
+	"\n	mov.w	%f1,%f0"
+	"\n	mulxu.w	%e2,%0"		/* khigh * xlow */
+	"\n	add.w	%e1,%f0"
+	"\n	mulxu.w	%f2,%1"		/* klow * xlow */
+	"\n	add.w	%f0,%e1"
+	: "=&r" (temp), "=r" (x)
+	: "%r" (GOLDEN_RATIO_32), "1" (x));
+	return x;
+}
+
+#endif
+#endif /* _ASM_HASH_H */