037f637767
The ARM architected timer can generate events (used for waking up
CPUs executing the wfe instruction) at a frequency represented as a
power-of-2 divisor of the clock rate.
An event stream might be used:
- To implement wfe-based timeouts for userspace locking implementations.
- To impose a timeout on a wfe for safeguarding against any programming
error in case an expected event is not generated.
This patch computes the event stream frequency aiming for a period
of 100us between events. It uses ARM/ARM64 specific backends to configure
and enable the event stream.
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[sudeep: moving ARM/ARM64 changes into separate patches
and adding Kconfig option]
Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
71 lines
2 KiB
C
71 lines
2 KiB
C
/*
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* Copyright (C) 2012 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __CLKSOURCE_ARM_ARCH_TIMER_H
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#define __CLKSOURCE_ARM_ARCH_TIMER_H
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#include <linux/clocksource.h>
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#include <linux/types.h>
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#define ARCH_TIMER_CTRL_ENABLE (1 << 0)
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#define ARCH_TIMER_CTRL_IT_MASK (1 << 1)
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#define ARCH_TIMER_CTRL_IT_STAT (1 << 2)
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enum arch_timer_reg {
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ARCH_TIMER_REG_CTRL,
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ARCH_TIMER_REG_TVAL,
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};
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#define ARCH_TIMER_PHYS_ACCESS 0
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#define ARCH_TIMER_VIRT_ACCESS 1
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#define ARCH_TIMER_MEM_PHYS_ACCESS 2
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#define ARCH_TIMER_MEM_VIRT_ACCESS 3
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#define ARCH_TIMER_USR_PCT_ACCESS_EN (1 << 0) /* physical counter */
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#define ARCH_TIMER_USR_VCT_ACCESS_EN (1 << 1) /* virtual counter */
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#define ARCH_TIMER_VIRT_EVT_EN (1 << 2)
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#define ARCH_TIMER_EVT_TRIGGER_SHIFT (4)
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#define ARCH_TIMER_EVT_TRIGGER_MASK (0xF << ARCH_TIMER_EVT_TRIGGER_SHIFT)
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#define ARCH_TIMER_USR_VT_ACCESS_EN (1 << 8) /* virtual timer registers */
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#define ARCH_TIMER_USR_PT_ACCESS_EN (1 << 9) /* physical timer registers */
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#define ARCH_TIMER_EVT_STREAM_FREQ 10000 /* 100us */
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#ifdef CONFIG_ARM_ARCH_TIMER
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extern u32 arch_timer_get_rate(void);
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extern u64 (*arch_timer_read_counter)(void);
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extern struct timecounter *arch_timer_get_timecounter(void);
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#else
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static inline u32 arch_timer_get_rate(void)
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{
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return 0;
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}
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static inline u64 arch_timer_read_counter(void)
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{
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return 0;
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}
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static inline struct timecounter *arch_timer_get_timecounter(void)
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{
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return NULL;
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}
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#endif
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#endif
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