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Diffstat (limited to 'arch/v850/kernel/highres_timer.c')
| -rw-r--r-- | arch/v850/kernel/highres_timer.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/arch/v850/kernel/highres_timer.c b/arch/v850/kernel/highres_timer.c new file mode 100644 index 000000000000..b16ad1eaf966 --- /dev/null +++ b/arch/v850/kernel/highres_timer.c @@ -0,0 +1,132 @@ +/* + * arch/v850/kernel/highres_timer.c -- High resolution timing routines + * + * Copyright (C) 2001,02,03 NEC Electronics Corporation + * Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org> + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file COPYING in the main directory of this + * archive for more details. + * + * Written by Miles Bader <miles@gnu.org> + */ + +#include <asm/system.h> +#include <asm/v850e_timer_d.h> +#include <asm/highres_timer.h> + +#define HIGHRES_TIMER_USEC_SHIFT 12 + +/* Pre-calculated constant used for converting ticks to real time + units. We initialize it to prevent it being put into BSS. */ +static u32 highres_timer_usec_prescale = 1; + +void highres_timer_slow_tick_irq (void) __attribute__ ((noreturn)); +void highres_timer_slow_tick_irq (void) +{ + /* This is an interrupt handler, so it must be very careful to + not to trash any registers. At this point, the stack-pointer + (r3) has been saved in the chip ram location ENTRY_SP by the + interrupt vector, so we can use it as a scratch register; we + must also restore it before returning. */ + asm ("ld.w %0[r0], sp;" + "add 1, sp;" + "st.w sp, %0[r0];" + "ld.w %1[r0], sp;" /* restore pre-irq stack-pointer */ + "reti" + :: + "i" (HIGHRES_TIMER_SLOW_TICKS_ADDR), + "i" (ENTRY_SP_ADDR) + : "memory"); +} + +void highres_timer_reset (void) +{ + V850E_TIMER_D_TMD (HIGHRES_TIMER_TIMER_D_UNIT) = 0; + HIGHRES_TIMER_SLOW_TICKS = 0; +} + +void highres_timer_start (void) +{ + u32 fast_tick_rate; + + /* Start hardware timer. */ + v850e_timer_d_configure (HIGHRES_TIMER_TIMER_D_UNIT, + HIGHRES_TIMER_SLOW_TICK_RATE); + + fast_tick_rate = + (V850E_TIMER_D_BASE_FREQ + >> V850E_TIMER_D_DIVLOG2 (HIGHRES_TIMER_TIMER_D_UNIT)); + + /* The obvious way of calculating microseconds from fast ticks + is to do: + + usec = fast_ticks * 10^6 / fast_tick_rate + + However, divisions are much slower than multiplications, and + the above calculation can overflow, so we do this instead: + + usec = fast_ticks * (10^6 * 2^12 / fast_tick_rate) / 2^12 + + since we can pre-calculate (10^6 * (2^12 / fast_tick_rate)) + and use a shift for dividing by 2^12, this avoids division, + and is almost as accurate (it differs by about 2 microseconds + at the extreme value of the fast-tick counter's ranger). */ + highres_timer_usec_prescale = ((1000000 << HIGHRES_TIMER_USEC_SHIFT) + / fast_tick_rate); + + /* Enable the interrupt (which is hardwired to this use), and + give it the highest priority. */ + V850E_INTC_IC (IRQ_INTCMD (HIGHRES_TIMER_TIMER_D_UNIT)) = 0; +} + +void highres_timer_stop (void) +{ + /* Stop the timer. */ + V850E_TIMER_D_TMCD (HIGHRES_TIMER_TIMER_D_UNIT) = + V850E_TIMER_D_TMCD_CAE; + /* Disable its interrupt, just in case. */ + v850e_intc_disable_irq (IRQ_INTCMD (HIGHRES_TIMER_TIMER_D_UNIT)); +} + +inline void highres_timer_read_ticks (u32 *slow_ticks, u32 *fast_ticks) +{ + int flags; + u32 fast_ticks_1, fast_ticks_2, _slow_ticks; + + local_irq_save (flags); + fast_ticks_1 = V850E_TIMER_D_TMD (HIGHRES_TIMER_TIMER_D_UNIT); + _slow_ticks = HIGHRES_TIMER_SLOW_TICKS; + fast_ticks_2 = V850E_TIMER_D_TMD (HIGHRES_TIMER_TIMER_D_UNIT); + local_irq_restore (flags); + + if (fast_ticks_2 < fast_ticks_1) + _slow_ticks++; + + *slow_ticks = _slow_ticks; + *fast_ticks = fast_ticks_2; +} + +inline void highres_timer_ticks_to_timeval (u32 slow_ticks, u32 fast_ticks, + struct timeval *tv) +{ + unsigned long sec, sec_rem, usec; + + usec = ((fast_ticks * highres_timer_usec_prescale) + >> HIGHRES_TIMER_USEC_SHIFT); + + sec = slow_ticks / HIGHRES_TIMER_SLOW_TICK_RATE; + sec_rem = slow_ticks % HIGHRES_TIMER_SLOW_TICK_RATE; + + usec += sec_rem * (1000000 / HIGHRES_TIMER_SLOW_TICK_RATE); + + tv->tv_sec = sec; + tv->tv_usec = usec; +} + +void highres_timer_read (struct timeval *tv) +{ + u32 fast_ticks, slow_ticks; + highres_timer_read_ticks (&slow_ticks, &fast_ticks); + highres_timer_ticks_to_timeval (slow_ticks, fast_ticks, tv); +} |