Release 4.7 drivers/clocksource/vf_pit_timer.c
/*
* Copyright 2012-2013 Freescale Semiconductor, Inc.
*
* 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.
*/
#include <linux/interrupt.h>
#include <linux/clockchips.h>
#include <linux/clk.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/sched_clock.h>
/*
* Each pit takes 0x10 Bytes register space
*/
#define PITMCR 0x00
#define PIT0_OFFSET 0x100
#define PITn_OFFSET(n) (PIT0_OFFSET + 0x10 * (n))
#define PITLDVAL 0x00
#define PITCVAL 0x04
#define PITTCTRL 0x08
#define PITTFLG 0x0c
#define PITMCR_MDIS (0x1 << 1)
#define PITTCTRL_TEN (0x1 << 0)
#define PITTCTRL_TIE (0x1 << 1)
#define PITCTRL_CHN (0x1 << 2)
#define PITTFLG_TIF 0x1
static void __iomem *clksrc_base;
static void __iomem *clkevt_base;
static unsigned long cycle_per_jiffy;
static inline void pit_timer_enable(void)
{
__raw_writel(PITTCTRL_TEN | PITTCTRL_TIE, clkevt_base + PITTCTRL);
}
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static inline void pit_timer_disable(void)
{
__raw_writel(0, clkevt_base + PITTCTRL);
}
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static inline void pit_irq_acknowledge(void)
{
__raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG);
}
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static u64 notrace pit_read_sched_clock(void)
{
return ~__raw_readl(clksrc_base + PITCVAL);
}
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static int __init pit_clocksource_init(unsigned long rate)
{
/* set the max load value and start the clock source counter */
__raw_writel(0, clksrc_base + PITTCTRL);
__raw_writel(~0UL, clksrc_base + PITLDVAL);
__raw_writel(PITTCTRL_TEN, clksrc_base + PITTCTRL);
sched_clock_register(pit_read_sched_clock, 32, rate);
return clocksource_mmio_init(clksrc_base + PITCVAL, "vf-pit", rate,
300, 32, clocksource_mmio_readl_down);
}
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static int pit_set_next_event(unsigned long delta,
struct clock_event_device *unused)
{
/*
* set a new value to PITLDVAL register will not restart the timer,
* to abort the current cycle and start a timer period with the new
* value, the timer must be disabled and enabled again.
* and the PITLAVAL should be set to delta minus one according to pit
* hardware requirement.
*/
pit_timer_disable();
__raw_writel(delta - 1, clkevt_base + PITLDVAL);
pit_timer_enable();
return 0;
}
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static int pit_shutdown(struct clock_event_device *evt)
{
pit_timer_disable();
return 0;
}
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static int pit_set_periodic(struct clock_event_device *evt)
{
pit_set_next_event(cycle_per_jiffy, evt);
return 0;
}
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static irqreturn_t pit_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = dev_id;
pit_irq_acknowledge();
/*
* pit hardware doesn't support oneshot, it will generate an interrupt
* and reload the counter value from PITLDVAL when PITCVAL reach zero,
* and start the counter again. So software need to disable the timer
* to stop the counter loop in ONESHOT mode.
*/
if (likely(clockevent_state_oneshot(evt)))
pit_timer_disable();
evt->event_handler(evt);
return IRQ_HANDLED;
}
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static struct clock_event_device clockevent_pit = {
.name = "VF pit timer",
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
.set_state_shutdown = pit_shutdown,
.set_state_periodic = pit_set_periodic,
.set_next_event = pit_set_next_event,
.rating = 300,
};
static struct irqaction pit_timer_irq = {
.name = "VF pit timer",
.flags = IRQF_TIMER | IRQF_IRQPOLL,
.handler = pit_timer_interrupt,
.dev_id = &clockevent_pit,
};
static int __init pit_clockevent_init(unsigned long rate, int irq)
{
__raw_writel(0, clkevt_base + PITTCTRL);
__raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG);
BUG_ON(setup_irq(irq, &pit_timer_irq));
clockevent_pit.cpumask = cpumask_of(0);
clockevent_pit.irq = irq;
/*
* The value for the LDVAL register trigger is calculated as:
* LDVAL trigger = (period / clock period) - 1
* The pit is a 32-bit down count timer, when the conter value
* reaches 0, it will generate an interrupt, thus the minimal
* LDVAL trigger value is 1. And then the min_delta is
* minimal LDVAL trigger value + 1, and the max_delta is full 32-bit.
*/
clockevents_config_and_register(&clockevent_pit, rate, 2, 0xffffffff);
return 0;
}
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static void __init pit_timer_init(struct device_node *np)
{
struct clk *pit_clk;
void __iomem *timer_base;
unsigned long clk_rate;
int irq;
timer_base = of_iomap(np, 0);
BUG_ON(!timer_base);
/*
* PIT0 and PIT1 can be chained to build a 64-bit timer,
* so choose PIT2 as clocksource, PIT3 as clockevent device,
* and leave PIT0 and PIT1 unused for anyone else who needs them.
*/
clksrc_base = timer_base + PITn_OFFSET(2);
clkevt_base = timer_base + PITn_OFFSET(3);
irq = irq_of_parse_and_map(np, 0);
BUG_ON(irq <= 0);
pit_clk = of_clk_get(np, 0);
BUG_ON(IS_ERR(pit_clk));
BUG_ON(clk_prepare_enable(pit_clk));
clk_rate = clk_get_rate(pit_clk);
cycle_per_jiffy = clk_rate / (HZ);
/* enable the pit module */
__raw_writel(~PITMCR_MDIS, timer_base + PITMCR);
BUG_ON(pit_clocksource_init(clk_rate));
pit_clockevent_init(clk_rate, irq);
}
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CLOCKSOURCE_OF_DECLARE(vf610, "fsl,vf610-pit", pit_timer_init);
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