0d651e4e65
Switching between reading the virtual or physical counters is problematic, as some core code wants a view of time before we're fully set up. Using a function pointer and switching the source after the first read can make time appear to go backwards, and having a check in the read function is an unfortunate block on what we want to be a fast path. Instead, this patch makes us always use the virtual counters. If we're a guest, or don't have hyp mode, we'll use the virtual timers, and as such don't care about CNTVOFF as long as it doesn't change in such a way as to make time appear to travel backwards. As the guest will use the virtual timers, a (potential) KVM host must use the physical timers (which can wake up the host even if they fire while a guest is executing), and hence a host must have CNTVOFF set to zero so as to have a consistent view of time between the physical timers and virtual counters. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Marc Zyngier <marc.zyngier@arm.com> Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Cc: Rob Herring <rob.herring@calxeda.com>
57 lines
1.4 KiB
C
57 lines
1.4 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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#define ARCH_TIMER_REG_CTRL 0
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#define ARCH_TIMER_REG_TVAL 1
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#define ARCH_TIMER_PHYS_ACCESS 0
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#define ARCH_TIMER_VIRT_ACCESS 1
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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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