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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: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Ard Biesheuvel 2017-03-19 17:23:31 +01:00 committed by Russell King
parent dd59f974bd
commit ea2d9a96b6
2 changed files with 39 additions and 0 deletions
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1
arch/arm/Kconfig
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@ -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

38
arch/arm/include/asm/cpufeature.h Normal file
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@ -0,0 +1,38 @@
/*
* 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