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openrisc: remove muldiv64()

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Originally, timers were ticks based, and it made sense to
add ticks to current time to know when to trigger an alarm.

But since commit:

7447545 change all other clock references to use nanosecond resolution accessors

All timers use nanoseconds and we need to convert ticks to nanoseconds, by
doing something like:

    y = muldiv64(x, get_ticks_per_sec(), TIMER_FREQ)

where x is the number of device ticks and y the number of system ticks.

y is used as nanoseconds in timer functions,
it works because 1 tick is 1 nanosecond.
(get_ticks_per_sec() is 10^9)

But as openrisc timer frequency is 20 MHz, we can also do:

    y = x * 50; /* 20 MHz period is 50 ns */

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
This commit is contained in:
Laurent Vivier 2015-08-25 17:17:15 +02:00
parent 683dca6bd5
commit ccaf174923
1 changed files with 3 additions and 4 deletions
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7
hw/openrisc/cputimer.c
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@ -22,7 +22,7 @@
#include "hw/hw.h" #include "hw/hw.h"
#include "qemu/timer.h" #include "qemu/timer.h"
#define TIMER_FREQ (20 * 1000 * 1000) /* 20MHz */ #define TIMER_PERIOD 50 /* 50 ns period for 20 MHz timer */
/* The time when TTCR changes */ /* The time when TTCR changes */
static uint64_t last_clk; static uint64_t last_clk;
@ -36,8 +36,7 @@ void cpu_openrisc_count_update(OpenRISCCPU *cpu)
return; return;
} }
now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
cpu->env.ttcr += (uint32_t)muldiv64(now - last_clk, TIMER_FREQ, cpu->env.ttcr += (uint32_t)((now - last_clk) / TIMER_PERIOD);
get_ticks_per_sec());
last_clk = now; last_clk = now;
} }
@ -59,7 +58,7 @@ void cpu_openrisc_timer_update(OpenRISCCPU *cpu)
} else { } else {
wait = (cpu->env.ttmr & TTMR_TP) - (cpu->env.ttcr & TTMR_TP); wait = (cpu->env.ttmr & TTMR_TP) - (cpu->env.ttcr & TTMR_TP);
} }
next = now + muldiv64(wait, get_ticks_per_sec(), TIMER_FREQ); next = now + (uint64_t)wait * TIMER_PERIOD;
timer_mod(cpu->env.timer, next); timer_mod(cpu->env.timer, next);
} }