powerpc: Implement arch_get_random_long/int() for powernv

Add the plumbing to implement arch_get_random_long/int(). It didn't seem
worth adding an extra ppc_md hook for int, so we reuse the one for long.

Add an implementation for powernv based on the hwrng found in power7+
systems. We whiten the output of the hwrng, and the result passes all
the dieharder tests.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 36 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
new file mode 100644
index 00000000000..d853d163ba4
--- /dev/null
+++ b/arch/powerpc/include/asm/archrandom.h
@@ -0,0 +1,32 @@
+#ifndef _ASM_POWERPC_ARCHRANDOM_H
+#define _ASM_POWERPC_ARCHRANDOM_H
+
+#ifdef CONFIG_ARCH_RANDOM
+
+#include <asm/machdep.h>
+
+static inline int arch_get_random_long(unsigned long *v)
+{
+	if (ppc_md.get_random_long)
+		return ppc_md.get_random_long(v);
+
+	return 0;
+}
+
+static inline int arch_get_random_int(unsigned int *v)
+{
+	unsigned long val;
+	int rc;
+
+	rc = arch_get_random_long(&val);
+	if (rc)
+		*v = val;
+
+	return rc;
+}
+
+int powernv_get_random_long(unsigned long *v);
+
+#endif /* CONFIG_ARCH_RANDOM */
+
+#endif /* _ASM_POWERPC_ARCHRANDOM_H */
diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
index 8b480901165..ce6cc2a7b8b 100644
--- a/arch/powerpc/include/asm/machdep.h
+++ b/arch/powerpc/include/asm/machdep.h
@@ -263,6 +263,10 @@ struct machdep_calls {
 	ssize_t (*cpu_probe)(const char *, size_t);
 	ssize_t (*cpu_release)(const char *, size_t);
 #endif
+
+#ifdef CONFIG_ARCH_RANDOM
+	int (*get_random_long)(unsigned long *v);
+#endif
 };
 
 extern void e500_idle(void);