mirror of
https://github.com/torvalds/linux.git
synced 2024-12-18 09:02:17 +00:00
56942fec06
The current timer-based delay loop relies on the architected timer to initiate the switch away from the polling-based implementation. This is unfortunate for platforms without the architected timers but with a suitable delay source (that is, constant frequency, always powered-up and ticking as long as the CPUs are online). This patch introduces a registration mechanism for the delay timer (which provides an unconditional read_current_timer implementation) and updates the architected timer code to use the new interface. Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Jonathan Austin <jonathan.austin@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
/*
|
|
* Copyright (C) 1995-2004 Russell King
|
|
*
|
|
* Delay routines, using a pre-computed "loops_per_second" value.
|
|
*/
|
|
#ifndef __ASM_ARM_DELAY_H
|
|
#define __ASM_ARM_DELAY_H
|
|
|
|
#include <asm/memory.h>
|
|
#include <asm/param.h> /* HZ */
|
|
|
|
#define MAX_UDELAY_MS 2
|
|
#define UDELAY_MULT ((UL(2199023) * HZ) >> 11)
|
|
#define UDELAY_SHIFT 30
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
struct delay_timer {
|
|
unsigned long (*read_current_timer)(void);
|
|
unsigned long freq;
|
|
};
|
|
|
|
extern struct arm_delay_ops {
|
|
void (*delay)(unsigned long);
|
|
void (*const_udelay)(unsigned long);
|
|
void (*udelay)(unsigned long);
|
|
} arm_delay_ops;
|
|
|
|
#define __delay(n) arm_delay_ops.delay(n)
|
|
|
|
/*
|
|
* This function intentionally does not exist; if you see references to
|
|
* it, it means that you're calling udelay() with an out of range value.
|
|
*
|
|
* With currently imposed limits, this means that we support a max delay
|
|
* of 2000us. Further limits: HZ<=1000 and bogomips<=3355
|
|
*/
|
|
extern void __bad_udelay(void);
|
|
|
|
/*
|
|
* division by multiplication: you don't have to worry about
|
|
* loss of precision.
|
|
*
|
|
* Use only for very small delays ( < 2 msec). Should probably use a
|
|
* lookup table, really, as the multiplications take much too long with
|
|
* short delays. This is a "reasonable" implementation, though (and the
|
|
* first constant multiplications gets optimized away if the delay is
|
|
* a constant)
|
|
*/
|
|
#define __udelay(n) arm_delay_ops.udelay(n)
|
|
#define __const_udelay(n) arm_delay_ops.const_udelay(n)
|
|
|
|
#define udelay(n) \
|
|
(__builtin_constant_p(n) ? \
|
|
((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \
|
|
__const_udelay((n) * UDELAY_MULT)) : \
|
|
__udelay(n))
|
|
|
|
/* Loop-based definitions for assembly code. */
|
|
extern void __loop_delay(unsigned long loops);
|
|
extern void __loop_udelay(unsigned long usecs);
|
|
extern void __loop_const_udelay(unsigned long);
|
|
|
|
/* Delay-loop timer registration. */
|
|
#define ARCH_HAS_READ_CURRENT_TIMER
|
|
extern void register_current_timer_delay(const struct delay_timer *timer);
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
|
|
#endif /* defined(_ARM_DELAY_H) */
|
|
|