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70264367a2
When udelay() is implemented using an architected timer, it is wrong to scale loops_per_jiffy when changing the CPU clock frequency since the timer clock remains constant. The lpj should probably become an implementation detail relevant to the CPU loop based delay routine only and more confined to it. In the mean time this is the minimal fix needed to have expected delays with the timer based implementation when cpufreq is also in use. Reported-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> Tested-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Liviu Dudau <Liviu.Dudau@arm.com> Cc: stable@vger.kernel.org Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
73 lines
2.0 KiB
C
73 lines
2.0 KiB
C
/*
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* Copyright (C) 1995-2004 Russell King
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*
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* Delay routines, using a pre-computed "loops_per_second" value.
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*/
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#ifndef __ASM_ARM_DELAY_H
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#define __ASM_ARM_DELAY_H
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#include <asm/memory.h>
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#include <asm/param.h> /* HZ */
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#define MAX_UDELAY_MS 2
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#define UDELAY_MULT ((UL(2199023) * HZ) >> 11)
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#define UDELAY_SHIFT 30
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#ifndef __ASSEMBLY__
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struct delay_timer {
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unsigned long (*read_current_timer)(void);
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unsigned long freq;
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};
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extern struct arm_delay_ops {
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void (*delay)(unsigned long);
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void (*const_udelay)(unsigned long);
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void (*udelay)(unsigned long);
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bool const_clock;
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} arm_delay_ops;
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#define __delay(n) arm_delay_ops.delay(n)
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/*
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* This function intentionally does not exist; if you see references to
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* it, it means that you're calling udelay() with an out of range value.
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*
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* With currently imposed limits, this means that we support a max delay
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* of 2000us. Further limits: HZ<=1000 and bogomips<=3355
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*/
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extern void __bad_udelay(void);
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/*
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* division by multiplication: you don't have to worry about
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* loss of precision.
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*
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* Use only for very small delays ( < 2 msec). Should probably use a
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* lookup table, really, as the multiplications take much too long with
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* short delays. This is a "reasonable" implementation, though (and the
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* first constant multiplications gets optimized away if the delay is
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* a constant)
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*/
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#define __udelay(n) arm_delay_ops.udelay(n)
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#define __const_udelay(n) arm_delay_ops.const_udelay(n)
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#define udelay(n) \
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(__builtin_constant_p(n) ? \
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((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \
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__const_udelay((n) * UDELAY_MULT)) : \
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__udelay(n))
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/* Loop-based definitions for assembly code. */
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extern void __loop_delay(unsigned long loops);
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extern void __loop_udelay(unsigned long usecs);
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extern void __loop_const_udelay(unsigned long);
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/* Delay-loop timer registration. */
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#define ARCH_HAS_READ_CURRENT_TIMER
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extern void register_current_timer_delay(const struct delay_timer *timer);
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#endif /* __ASSEMBLY__ */
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#endif /* defined(_ARM_DELAY_H) */
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