![Nicolas Ferre](/assets/img/avatar_default.png)
Remove the unnecessary (void) cast on at91_st_read() return value. Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com> Acked-by: Ryan Mallon <rmallon@gmail.com>
221 lines
5.8 KiB
C
221 lines
5.8 KiB
C
/*
|
|
* linux/arch/arm/mach-at91/at91rm9200_time.c
|
|
*
|
|
* Copyright (C) 2003 SAN People
|
|
* Copyright (C) 2003 ATMEL
|
|
*
|
|
* 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; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* 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. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/irq.h>
|
|
#include <linux/clockchips.h>
|
|
|
|
#include <asm/mach/time.h>
|
|
|
|
#include <mach/at91_st.h>
|
|
|
|
static unsigned long last_crtr;
|
|
static u32 irqmask;
|
|
static struct clock_event_device clkevt;
|
|
|
|
#define RM9200_TIMER_LATCH ((AT91_SLOW_CLOCK + HZ/2) / HZ)
|
|
|
|
/*
|
|
* The ST_CRTR is updated asynchronously to the master clock ... but
|
|
* the updates as seen by the CPU don't seem to be strictly monotonic.
|
|
* Waiting until we read the same value twice avoids glitching.
|
|
*/
|
|
static inline unsigned long read_CRTR(void)
|
|
{
|
|
unsigned long x1, x2;
|
|
|
|
x1 = at91_st_read(AT91_ST_CRTR);
|
|
do {
|
|
x2 = at91_st_read(AT91_ST_CRTR);
|
|
if (x1 == x2)
|
|
break;
|
|
x1 = x2;
|
|
} while (1);
|
|
return x1;
|
|
}
|
|
|
|
/*
|
|
* IRQ handler for the timer.
|
|
*/
|
|
static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
|
|
{
|
|
u32 sr = at91_st_read(AT91_ST_SR) & irqmask;
|
|
|
|
/*
|
|
* irqs should be disabled here, but as the irq is shared they are only
|
|
* guaranteed to be off if the timer irq is registered first.
|
|
*/
|
|
WARN_ON_ONCE(!irqs_disabled());
|
|
|
|
/* simulate "oneshot" timer with alarm */
|
|
if (sr & AT91_ST_ALMS) {
|
|
clkevt.event_handler(&clkevt);
|
|
return IRQ_HANDLED;
|
|
}
|
|
|
|
/* periodic mode should handle delayed ticks */
|
|
if (sr & AT91_ST_PITS) {
|
|
u32 crtr = read_CRTR();
|
|
|
|
while (((crtr - last_crtr) & AT91_ST_CRTV) >= RM9200_TIMER_LATCH) {
|
|
last_crtr += RM9200_TIMER_LATCH;
|
|
clkevt.event_handler(&clkevt);
|
|
}
|
|
return IRQ_HANDLED;
|
|
}
|
|
|
|
/* this irq is shared ... */
|
|
return IRQ_NONE;
|
|
}
|
|
|
|
static struct irqaction at91rm9200_timer_irq = {
|
|
.name = "at91_tick",
|
|
.flags = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
|
|
.handler = at91rm9200_timer_interrupt
|
|
};
|
|
|
|
static cycle_t read_clk32k(struct clocksource *cs)
|
|
{
|
|
return read_CRTR();
|
|
}
|
|
|
|
static struct clocksource clk32k = {
|
|
.name = "32k_counter",
|
|
.rating = 150,
|
|
.read = read_clk32k,
|
|
.mask = CLOCKSOURCE_MASK(20),
|
|
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
|
|
};
|
|
|
|
static void
|
|
clkevt32k_mode(enum clock_event_mode mode, struct clock_event_device *dev)
|
|
{
|
|
/* Disable and flush pending timer interrupts */
|
|
at91_st_write(AT91_ST_IDR, AT91_ST_PITS | AT91_ST_ALMS);
|
|
at91_st_read(AT91_ST_SR);
|
|
|
|
last_crtr = read_CRTR();
|
|
switch (mode) {
|
|
case CLOCK_EVT_MODE_PERIODIC:
|
|
/* PIT for periodic irqs; fixed rate of 1/HZ */
|
|
irqmask = AT91_ST_PITS;
|
|
at91_st_write(AT91_ST_PIMR, RM9200_TIMER_LATCH);
|
|
break;
|
|
case CLOCK_EVT_MODE_ONESHOT:
|
|
/* ALM for oneshot irqs, set by next_event()
|
|
* before 32 seconds have passed
|
|
*/
|
|
irqmask = AT91_ST_ALMS;
|
|
at91_st_write(AT91_ST_RTAR, last_crtr);
|
|
break;
|
|
case CLOCK_EVT_MODE_SHUTDOWN:
|
|
case CLOCK_EVT_MODE_UNUSED:
|
|
case CLOCK_EVT_MODE_RESUME:
|
|
irqmask = 0;
|
|
break;
|
|
}
|
|
at91_st_write(AT91_ST_IER, irqmask);
|
|
}
|
|
|
|
static int
|
|
clkevt32k_next_event(unsigned long delta, struct clock_event_device *dev)
|
|
{
|
|
u32 alm;
|
|
int status = 0;
|
|
|
|
BUG_ON(delta < 2);
|
|
|
|
/* The alarm IRQ uses absolute time (now+delta), not the relative
|
|
* time (delta) in our calling convention. Like all clockevents
|
|
* using such "match" hardware, we have a race to defend against.
|
|
*
|
|
* Our defense here is to have set up the clockevent device so the
|
|
* delta is at least two. That way we never end up writing RTAR
|
|
* with the value then held in CRTR ... which would mean the match
|
|
* wouldn't trigger until 32 seconds later, after CRTR wraps.
|
|
*/
|
|
alm = read_CRTR();
|
|
|
|
/* Cancel any pending alarm; flush any pending IRQ */
|
|
at91_st_write(AT91_ST_RTAR, alm);
|
|
at91_st_read(AT91_ST_SR);
|
|
|
|
/* Schedule alarm by writing RTAR. */
|
|
alm += delta;
|
|
at91_st_write(AT91_ST_RTAR, alm);
|
|
|
|
return status;
|
|
}
|
|
|
|
static struct clock_event_device clkevt = {
|
|
.name = "at91_tick",
|
|
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
|
|
.shift = 32,
|
|
.rating = 150,
|
|
.set_next_event = clkevt32k_next_event,
|
|
.set_mode = clkevt32k_mode,
|
|
};
|
|
|
|
void __iomem *at91_st_base;
|
|
|
|
void __init at91rm9200_ioremap_st(u32 addr)
|
|
{
|
|
at91_st_base = ioremap(addr, 256);
|
|
if (!at91_st_base)
|
|
panic("Impossible to ioremap ST\n");
|
|
}
|
|
|
|
/*
|
|
* ST (system timer) module supports both clockevents and clocksource.
|
|
*/
|
|
void __init at91rm9200_timer_init(void)
|
|
{
|
|
/* Disable all timer interrupts, and clear any pending ones */
|
|
at91_st_write(AT91_ST_IDR,
|
|
AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS);
|
|
at91_st_read(AT91_ST_SR);
|
|
|
|
/* Make IRQs happen for the system timer */
|
|
setup_irq(AT91_ID_SYS, &at91rm9200_timer_irq);
|
|
|
|
/* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
|
|
* directly for the clocksource and all clockevents, after adjusting
|
|
* its prescaler from the 1 Hz default.
|
|
*/
|
|
at91_st_write(AT91_ST_RTMR, 1);
|
|
|
|
/* Setup timer clockevent, with minimum of two ticks (important!!) */
|
|
clkevt.mult = div_sc(AT91_SLOW_CLOCK, NSEC_PER_SEC, clkevt.shift);
|
|
clkevt.max_delta_ns = clockevent_delta2ns(AT91_ST_ALMV, &clkevt);
|
|
clkevt.min_delta_ns = clockevent_delta2ns(2, &clkevt) + 1;
|
|
clkevt.cpumask = cpumask_of(0);
|
|
clockevents_register_device(&clkevt);
|
|
|
|
/* register clocksource */
|
|
clocksource_register_hz(&clk32k, AT91_SLOW_CLOCK);
|
|
}
|
|
|
|
struct sys_timer at91rm9200_timer = {
|
|
.init = at91rm9200_timer_init,
|
|
};
|
|
|