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Commit ea2d9a96 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Russell King
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ARM: 8663/1: wire up HWCAP/HWCAP2 feature bits to the CPU modalias 



Wire up the generic support for exposing CPU feature bits via the
modalias in /sys/device/system/cpu. This allows udev to automatically
load modules for things like crypto algorithms that are implemented
using optional instructions.

Since it is non-trivial to transparantly support both HWCAP and HWCAP2
capabilities in the cpu_feature() macro (which allows a module's hwcap
dependency and init routine to be declared using a single invocation of
module_cpu_feature_match()), support only HWCAP2 for now, which covers
the capabilities that are most likely to be useful in this manner.
Module dependencies on HWCAP will need to be declared explicitly via a
MODULE_DEVICE_TABLE(cpu, ...) declaration.

Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
parent dd59f974

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ config ARM 
	select GENERIC_ALLOCATOR

	select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)

	select GENERIC_CLOCKEVENTS_BROADCAST if SMP

	select GENERIC_CPU_AUTOPROBE

	select GENERIC_EARLY_IOREMAP

	select GENERIC_IDLE_POLL_SETUP

	select GENERIC_IRQ_PROBE

arch/arm/include/asm/cpufeature.h

0 → 100644
+38 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#ifndef __ASM_CPUFEATURE_H

#define __ASM_CPUFEATURE_H



#include <linux/log2.h>

#include <asm/hwcap.h>



/*

 * Due to the fact that ELF_HWCAP is a 32-bit type on ARM, and given the number

 * of optional CPU features it defines, ARM's CPU hardware capability bits have

 * been distributed over separate elf_hwcap and elf_hwcap2 variables, each of

 * which covers a subset of the available CPU features.

 *

 * Currently, only a few of those are suitable for automatic module loading

 * (which is the primary use case of this facility) and those happen to be all

 * covered by HWCAP2. So let's only cover those via the cpu_feature()

 * convenience macro for now (which is used by module_cpu_feature_match()).

 * However, all capabilities are exposed via the modalias, and can be matched

 * using an explicit MODULE_DEVICE_TABLE() that uses __hwcap_feature() directly.

 */

#define MAX_CPU_FEATURES	64

#define __hwcap_feature(x)	ilog2(HWCAP_ ## x)

#define __hwcap2_feature(x)	(32 + ilog2(HWCAP2_ ## x))

#define cpu_feature(x)		__hwcap2_feature(x)



static inline bool cpu_have_feature(unsigned int num)

{

	return num < 32 ? elf_hwcap & BIT(num) : elf_hwcap2 & BIT(num - 32);

}



#endif