powerpc: Add module autoloading based on CPU features

BugLink: http://bugs.launchpad.net/bugs/1651322

This patch provides the necessary infrastructure to allow drivers
to be automatically loaded via udev. It implements the minimum
required to be able to use module_cpu_feature_match() to trigger
the GENERIC_CPU_AUTOPROBE mechanisms.

The features exposed are a mirror of the cpu_user_features
(converted to an offset from a mask). This decision was made to
ensure that the behavior between features for module loading and
userspace are consistent.
Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
[mpe: Only define the bits we currently need]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

(back ported from commit 4a120276)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

Conflicts:
	arch/powerpc/Kconfig
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: John Donnelly <john.donnelly@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

arch/powerpc/Kconfig

@@ -160,6 +160,7 @@ config PPC
 	select EDAC_ATOMIC_SCRUB
 	select ARCH_HAS_DMA_SET_COHERENT_MASK
 	select HAVE_ARCH_SECCOMP_FILTER
+	select GENERIC_CPU_AUTOPROBE
 
 config GENERIC_CSUM
 	def_bool CPU_LITTLE_ENDIAN

arch/powerpc/include/asm/cpufeature.h

+/*
+ * CPU feature definitions for module loading, used by
+ * module_cpu_feature_match(), see asm/cputable.h for powerpc CPU features.
+ *
+ * Copyright 2016 Alastair D'Silva, IBM Corporation.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifndef __ASM_POWERPC_CPUFEATURE_H
+#define __ASM_POWERPC_CPUFEATURE_H
+
+#include <asm/cputable.h>
+
+/* Keep these in step with powerpc/include/asm/cputable.h */
+#define MAX_CPU_FEATURES (2 * 32)
+
+/*
+ * Currently we don't have a need for any of the feature bits defined in
+ * cpu_user_features. When we do, they should be defined such as:
+ *
+ * #define PPC_MODULE_FEATURE_32 (ilog2(PPC_FEATURE_32))
+ */
+
+#define PPC_MODULE_FEATURE_VEC_CRYPTO			(32 + ilog2(PPC_FEATURE2_VEC_CRYPTO))
+
+#define cpu_feature(x)		(x)
+
+static inline bool cpu_have_feature(unsigned int num)
+{
+	if (num < 32)
+		return !!(cur_cpu_spec->cpu_user_features & 1UL << num);
+	else
+		return !!(cur_cpu_spec->cpu_user_features2 & 1UL << (num - 32));
+}
+
+#endif /* __ASM_POWERPC_CPUFEATURE_H */