268 lines
7.1 KiB
C
268 lines
7.1 KiB
C
/*
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* at91sam926x_time.c - Periodic Interval Timer (PIT) for at91sam926x
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*
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* Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France
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* Revision 2005 M. Nicolas Diremdjian, ATMEL Rousset, France
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* Converted to ClockSource/ClockEvents by David Brownell.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#define pr_fmt(fmt) "AT91: PIT: " fmt
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#include <linux/clk.h>
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#include <linux/clockchips.h>
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#include <linux/interrupt.h>
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#include <linux/irq.h>
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#include <linux/kernel.h>
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#include <linux/of.h>
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#include <linux/of_address.h>
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#include <linux/of_irq.h>
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#include <linux/slab.h>
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#define AT91_PIT_MR 0x00 /* Mode Register */
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#define AT91_PIT_PITIEN BIT(25) /* Timer Interrupt Enable */
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#define AT91_PIT_PITEN BIT(24) /* Timer Enabled */
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#define AT91_PIT_PIV GENMASK(19, 0) /* Periodic Interval Value */
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#define AT91_PIT_SR 0x04 /* Status Register */
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#define AT91_PIT_PITS BIT(0) /* Timer Status */
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#define AT91_PIT_PIVR 0x08 /* Periodic Interval Value Register */
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#define AT91_PIT_PIIR 0x0c /* Periodic Interval Image Register */
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#define AT91_PIT_PICNT GENMASK(31, 20) /* Interval Counter */
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#define AT91_PIT_CPIV GENMASK(19, 0) /* Inverval Value */
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#define PIT_CPIV(x) ((x) & AT91_PIT_CPIV)
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#define PIT_PICNT(x) (((x) & AT91_PIT_PICNT) >> 20)
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struct pit_data {
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struct clock_event_device clkevt;
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struct clocksource clksrc;
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void __iomem *base;
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u32 cycle;
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u32 cnt;
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unsigned int irq;
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struct clk *mck;
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};
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static inline struct pit_data *clksrc_to_pit_data(struct clocksource *clksrc)
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{
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return container_of(clksrc, struct pit_data, clksrc);
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}
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static inline struct pit_data *clkevt_to_pit_data(struct clock_event_device *clkevt)
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{
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return container_of(clkevt, struct pit_data, clkevt);
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}
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static inline unsigned int pit_read(void __iomem *base, unsigned int reg_offset)
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{
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return readl_relaxed(base + reg_offset);
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}
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static inline void pit_write(void __iomem *base, unsigned int reg_offset, unsigned long value)
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{
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writel_relaxed(value, base + reg_offset);
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}
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/*
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* Clocksource: just a monotonic counter of MCK/16 cycles.
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* We don't care whether or not PIT irqs are enabled.
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*/
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static u64 read_pit_clk(struct clocksource *cs)
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{
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struct pit_data *data = clksrc_to_pit_data(cs);
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unsigned long flags;
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u32 elapsed;
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u32 t;
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raw_local_irq_save(flags);
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elapsed = data->cnt;
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t = pit_read(data->base, AT91_PIT_PIIR);
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raw_local_irq_restore(flags);
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elapsed += PIT_PICNT(t) * data->cycle;
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elapsed += PIT_CPIV(t);
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return elapsed;
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}
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static int pit_clkevt_shutdown(struct clock_event_device *dev)
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{
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struct pit_data *data = clkevt_to_pit_data(dev);
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/* disable irq, leaving the clocksource active */
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pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
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return 0;
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}
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/*
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* Clockevent device: interrupts every 1/HZ (== pit_cycles * MCK/16)
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*/
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static int pit_clkevt_set_periodic(struct clock_event_device *dev)
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{
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struct pit_data *data = clkevt_to_pit_data(dev);
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/* update clocksource counter */
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data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
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pit_write(data->base, AT91_PIT_MR,
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(data->cycle - 1) | AT91_PIT_PITEN | AT91_PIT_PITIEN);
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return 0;
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}
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static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
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{
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struct pit_data *data = clkevt_to_pit_data(cedev);
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/* Disable timer */
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pit_write(data->base, AT91_PIT_MR, 0);
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}
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static void at91sam926x_pit_reset(struct pit_data *data)
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{
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/* Disable timer and irqs */
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pit_write(data->base, AT91_PIT_MR, 0);
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/* Clear any pending interrupts, wait for PIT to stop counting */
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while (PIT_CPIV(pit_read(data->base, AT91_PIT_PIVR)) != 0)
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cpu_relax();
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/* Start PIT but don't enable IRQ */
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pit_write(data->base, AT91_PIT_MR,
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(data->cycle - 1) | AT91_PIT_PITEN);
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}
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static void at91sam926x_pit_resume(struct clock_event_device *cedev)
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{
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struct pit_data *data = clkevt_to_pit_data(cedev);
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at91sam926x_pit_reset(data);
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}
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/*
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* IRQ handler for the timer.
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*/
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static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
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{
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struct pit_data *data = dev_id;
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/* The PIT interrupt may be disabled, and is shared */
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if (clockevent_state_periodic(&data->clkevt) &&
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(pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
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/* Get number of ticks performed before irq, and ack it */
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data->cnt += data->cycle * PIT_PICNT(pit_read(data->base,
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AT91_PIT_PIVR));
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data->clkevt.event_handler(&data->clkevt);
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return IRQ_HANDLED;
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}
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return IRQ_NONE;
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}
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/*
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* Set up both clocksource and clockevent support.
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*/
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static int __init at91sam926x_pit_dt_init(struct device_node *node)
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{
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unsigned long pit_rate;
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unsigned bits;
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int ret;
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struct pit_data *data;
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data = kzalloc(sizeof(*data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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data->base = of_iomap(node, 0);
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if (!data->base) {
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pr_err("Could not map PIT address\n");
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ret = -ENXIO;
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goto exit;
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}
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data->mck = of_clk_get(node, 0);
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if (IS_ERR(data->mck)) {
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pr_err("Unable to get mck clk\n");
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ret = PTR_ERR(data->mck);
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goto exit;
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}
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ret = clk_prepare_enable(data->mck);
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if (ret) {
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pr_err("Unable to enable mck\n");
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goto exit;
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}
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/* Get the interrupts property */
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data->irq = irq_of_parse_and_map(node, 0);
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if (!data->irq) {
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pr_err("Unable to get IRQ from DT\n");
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ret = -EINVAL;
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goto exit;
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}
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/*
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* Use our actual MCK to figure out how many MCK/16 ticks per
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* 1/HZ period (instead of a compile-time constant LATCH).
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*/
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pit_rate = clk_get_rate(data->mck) / 16;
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data->cycle = DIV_ROUND_CLOSEST(pit_rate, HZ);
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WARN_ON(((data->cycle - 1) & ~AT91_PIT_PIV) != 0);
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/* Initialize and enable the timer */
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at91sam926x_pit_reset(data);
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/*
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* Register clocksource. The high order bits of PIV are unused,
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* so this isn't a 32-bit counter unless we get clockevent irqs.
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*/
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bits = 12 /* PICNT */ + ilog2(data->cycle) /* PIV */;
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data->clksrc.mask = CLOCKSOURCE_MASK(bits);
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data->clksrc.name = "pit";
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data->clksrc.rating = 175;
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data->clksrc.read = read_pit_clk;
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data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
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ret = clocksource_register_hz(&data->clksrc, pit_rate);
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if (ret) {
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pr_err("Failed to register clocksource\n");
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goto exit;
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}
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/* Set up irq handler */
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ret = request_irq(data->irq, at91sam926x_pit_interrupt,
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IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
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"at91_tick", data);
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if (ret) {
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pr_err("Unable to setup IRQ\n");
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clocksource_unregister(&data->clksrc);
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goto exit;
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}
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/* Set up and register clockevents */
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data->clkevt.name = "pit";
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data->clkevt.features = CLOCK_EVT_FEAT_PERIODIC;
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data->clkevt.shift = 32;
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data->clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, data->clkevt.shift);
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data->clkevt.rating = 100;
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data->clkevt.cpumask = cpumask_of(0);
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data->clkevt.set_state_shutdown = pit_clkevt_shutdown;
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data->clkevt.set_state_periodic = pit_clkevt_set_periodic;
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data->clkevt.resume = at91sam926x_pit_resume;
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data->clkevt.suspend = at91sam926x_pit_suspend;
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clockevents_register_device(&data->clkevt);
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return 0;
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exit:
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kfree(data);
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return ret;
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}
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TIMER_OF_DECLARE(at91sam926x_pit, "atmel,at91sam9260-pit",
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at91sam926x_pit_dt_init);
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