d0a533b182
This patch allows a timer-based delay implementation to be selected by switching the delay routines over to use get_cycles, which is implemented in terms of read_current_timer. This further allows us to skip the loop calibration and have a consistent delay function in the face of core frequency scaling. To avoid the pain of dealing with memory-mapped counters, this implementation uses the co-processor interface to the architected timers when they are available. The previous loop-based implementation is kept around for CPUs without the architected timers and we retain both the maximum delay (2ms) and the corresponding conversion factors for determining the number of loops required for a given interval. Since the indirection of the timer routines will only work when called from C, the sa1100 sleep routines are modified to branch to the loop-based delay functions directly. Tested-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
62 lines
1.7 KiB
C
62 lines
1.7 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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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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} 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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#endif /* __ASSEMBLY__ */
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#endif /* defined(_ARM_DELAY_H) */
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