mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-09 01:59:41 +00:00
1337173148
The current implementations of __ndelay and __udelay call a hypervisor service to delay, but the hypervisor service isn't actually implemented very well, and the consensus is that Linux should handle figuring this out natively and not use a hypervisor service. By converting nanoseconds to cycles, and then spinning until the cycle counter reaches the desired cycle, we get several benefits: first, we are sensitive to the actual clock speed; second, we use less power by issuing a slow SPR read once every six cycles while we delay; and third, we properly handle the case of an interrupt by exiting at the target time rather than after some number of cycles. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
50 lines
1.6 KiB
C
50 lines
1.6 KiB
C
/*
|
|
* Copyright 2010 Tilera Corporation. All Rights Reserved.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation, version 2.
|
|
*
|
|
* This program is distributed in the hope that it will be useful, but
|
|
* WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
|
|
* NON INFRINGEMENT. See the GNU General Public License for
|
|
* more details.
|
|
*/
|
|
|
|
#ifndef _ASM_TILE_TIMEX_H
|
|
#define _ASM_TILE_TIMEX_H
|
|
|
|
/*
|
|
* This rate should be a multiple of the possible HZ values (100, 250, 1000)
|
|
* and a fraction of the possible hardware timer frequencies. Our timer
|
|
* frequency is highly tunable but also quite precise, so for the primary use
|
|
* of this value (setting ACT_HZ from HZ) we just pick a value that causes
|
|
* ACT_HZ to be set to HZ. We make the value somewhat large just to be
|
|
* more robust in case someone tries out a new value of HZ.
|
|
*/
|
|
#define CLOCK_TICK_RATE 1000000
|
|
|
|
typedef unsigned long long cycles_t;
|
|
|
|
#if CHIP_HAS_SPLIT_CYCLE()
|
|
cycles_t get_cycles(void);
|
|
#else
|
|
static inline cycles_t get_cycles(void)
|
|
{
|
|
return __insn_mfspr(SPR_CYCLE);
|
|
}
|
|
#endif
|
|
|
|
cycles_t get_clock_rate(void);
|
|
|
|
/* Convert nanoseconds to core clock cycles. */
|
|
cycles_t ns2cycles(unsigned long nsecs);
|
|
|
|
/* Called at cpu initialization to set some low-level constants. */
|
|
void setup_clock(void);
|
|
|
|
/* Called at cpu initialization to start the tile-timer clock device. */
|
|
void setup_tile_timer(void);
|
|
|
|
#endif /* _ASM_TILE_TIMEX_H */
|