MIPS: Enable GENERIC_CPU_AUTOPROBE

Add missing macros and methods that are required by
CONFIG_GENERIC_CPU_AUTOPROBE: MAX_CPU_FEATURES, cpu_have_feature(),
cpu_feature().

Also set a default elf platform as currently it is not set for most MIPS
platforms resulting in incorrectly specified modalias values in cpu
autoprobe ("cpu:type:(null):feature:...").

Export 'elf_hwcap' symbol so that it can be accessed from modules that
use module_cpu_feature_match()

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15395/

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -46,6 +46,7 @@ config MIPS
 	select ARCH_DISCARD_MEMBLOCK
 	select GENERIC_SMP_IDLE_THREAD
 	select BUILDTIME_EXTABLE_SORT
+	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_SCHED_CLOCK if !CAVIUM_OCTEON_SOC
 	select GENERIC_CMOS_UPDATE

arch/mips/include/asm/cpufeature.h

@@ -0,0 +1,26 @@
+/*
+ * CPU feature definitions for module loading, used by
+ * module_cpu_feature_match(), see uapi/asm/hwcap.h for MIPS CPU features.
+ *
+ * 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_CPUFEATURE_H
+#define __ASM_CPUFEATURE_H
+
+#include <uapi/asm/hwcap.h>
+#include <asm/elf.h>
+
+#define MAX_CPU_FEATURES (8 * sizeof(elf_hwcap))
+
+#define cpu_feature(x)		ilog2(HWCAP_ ## x)
+
+static inline bool cpu_have_feature(unsigned int num)
+{
+	return elf_hwcap & (1UL << num);
+}
+
+#endif /* __ASM_CPUFEATURE_H */

arch/mips/kernel/cpu-probe.c

@@ -34,6 +34,7 @@
 
 /* Hardware capabilities */
 unsigned int elf_hwcap __read_mostly;
+EXPORT_SYMBOL_GPL(elf_hwcap);
 
 /*
  * Get the FPU Implementation/Revision.
@@ -1946,6 +1947,12 @@ void cpu_probe(void)
 	struct cpuinfo_mips *c = &current_cpu_data;
 	unsigned int cpu = smp_processor_id();
 
+	/*
+	 * Set a default elf platform, cpu probe may later
+	 * overwrite it with a more precise value
+	 */
+	set_elf_platform(cpu, "mips");
+
 	c->processor_id = PRID_IMP_UNKNOWN;
 	c->fpu_id	= FPIR_IMP_NONE;
 	c->cputype	= CPU_UNKNOWN;