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/*
* Copyright (C) 2012 Broadcom Corporation
*
* 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 "as is" WITHOUT ANY WARRANTY of any
* kind, whether express or implied; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/clockchips.h>
#include <linux/types.h>
#include <linux/io.h>
#include <asm/mach/time.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#define KONA_GPTIMER_STCS_OFFSET 0x00000000
#define KONA_GPTIMER_STCLO_OFFSET 0x00000004
#define KONA_GPTIMER_STCHI_OFFSET 0x00000008
#define KONA_GPTIMER_STCM0_OFFSET 0x0000000C
#define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT 0
#define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT 4
struct kona_bcm_timers {
int tmr_irq;
void __iomem *tmr_regs;
};
static struct kona_bcm_timers timers;
static u32 arch_timer_rate;
/*
* We use the peripheral timers for system tick, the cpu global timer for
* profile tick
*/
static void kona_timer_disable_and_clear(void __iomem *base)
{
uint32_t reg;
/*
* clear and disable interrupts
* We are using compare/match register 0 for our system interrupts
*/
reg = readl(base + KONA_GPTIMER_STCS_OFFSET);
/* Clear compare (0) interrupt */
reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT;
/* disable compare */
reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
writel(reg, base + KONA_GPTIMER_STCS_OFFSET);
}
static void
kona_timer_get_counter(void *timer_base, uint32_t *msw, uint32_t *lsw)
{
void __iomem *base = IOMEM(timer_base);
int loop_limit = 4;
/*
* Read 64-bit free running counter
* 1. Read hi-word
* 2. Read low-word
* 3. Read hi-word again
* 4.1
* if new hi-word is not equal to previously read hi-word, then
* start from #1
* 4.2
* if new hi-word is equal to previously read hi-word then stop.
*/
while (--loop_limit) {
*msw = readl(base + KONA_GPTIMER_STCHI_OFFSET);
*lsw = readl(base + KONA_GPTIMER_STCLO_OFFSET);
if (*msw == readl(base + KONA_GPTIMER_STCHI_OFFSET))
break;
}
if (!loop_limit) {
pr_err("bcm_kona_timer: getting counter failed.\n");
pr_err(" Timer will be impacted\n");
}
return;
}
static const struct of_device_id bcm_timer_ids[] __initconst = {
{.compatible = "bcm,kona-timer"},
{},
};
static void __init kona_timers_init(struct device_node *node)
{
u32 freq;
if (!of_property_read_u32(node, "clock-frequency", &freq))
arch_timer_rate = freq;
else
panic("clock-frequency not set in the .dts file");
/* Setup IRQ numbers */
timers.tmr_irq = irq_of_parse_and_map(node, 0);
/* Setup IO addresses */
timers.tmr_regs = of_iomap(node, 0);
kona_timer_disable_and_clear(timers.tmr_regs);
}
static int kona_timer_set_next_event(unsigned long clc,
struct clock_event_device *unused)
{
/*
* timer (0) is disabled by the timer interrupt already
* so, here we reload the next event value and re-enable
* the timer.
*
* This way, we are potentially losing the time between
* timer-interrupt->set_next_event. CPU local timers, when
* they come in should get rid of skew.
*/
uint32_t lsw, msw;
uint32_t reg;
kona_timer_get_counter(timers.tmr_regs, &msw, &lsw);
/* Load the "next" event tick value */
writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET);
/* Enable compare */
reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT);
writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET);
return 0;
}
static void kona_timer_set_mode(enum clock_event_mode mode,
struct clock_event_device *unused)
{
switch (mode) {
case CLOCK_EVT_MODE_ONESHOT:
/* by default mode is one shot don't do any thing */
break;
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
default:
kona_timer_disable_and_clear(timers.tmr_regs);
}
}
static struct clock_event_device kona_clockevent_timer = {
.name = "timer 1",
.features = CLOCK_EVT_FEAT_ONESHOT,
.set_next_event = kona_timer_set_next_event,
.set_mode = kona_timer_set_mode
};
static void __init kona_timer_clockevents_init(void)
{
kona_clockevent_timer.cpumask = cpumask_of(0);
clockevents_config_and_register(&kona_clockevent_timer,
arch_timer_rate, 6, 0xffffffff);
}
static irqreturn_t kona_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = &kona_clockevent_timer;
kona_timer_disable_and_clear(timers.tmr_regs);
evt->event_handler(evt);
return IRQ_HANDLED;
}
static struct irqaction kona_timer_irq = {
.name = "Kona Timer Tick",
.flags = IRQF_TIMER,
.handler = kona_timer_interrupt,
};
static void __init kona_timer_init(struct device_node *node)
{
kona_timers_init(node);
kona_timer_clockevents_init();
setup_irq(timers.tmr_irq, &kona_timer_irq);
kona_timer_set_next_event((arch_timer_rate / HZ), NULL);
}
CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init);
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