337 lines
8.6 KiB
C
337 lines
8.6 KiB
C
/*
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* drivers/clocksource/arm_global_timer.c
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*
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* Copyright (C) 2013 STMicroelectronics (R&D) Limited.
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* Author: Stuart Menefy <stuart.menefy@st.com>
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* Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>
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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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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/clocksource.h>
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#include <linux/clockchips.h>
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#include <linux/cpu.h>
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#include <linux/clk.h>
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#include <linux/err.h>
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#include <linux/io.h>
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#include <linux/of.h>
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#include <linux/of_irq.h>
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#include <linux/of_address.h>
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#include <linux/sched_clock.h>
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#include <asm/cputype.h>
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#define GT_COUNTER0 0x00
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#define GT_COUNTER1 0x04
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#define GT_CONTROL 0x08
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#define GT_CONTROL_TIMER_ENABLE BIT(0) /* this bit is NOT banked */
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#define GT_CONTROL_COMP_ENABLE BIT(1) /* banked */
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#define GT_CONTROL_IRQ_ENABLE BIT(2) /* banked */
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#define GT_CONTROL_AUTO_INC BIT(3) /* banked */
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#define GT_INT_STATUS 0x0c
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#define GT_INT_STATUS_EVENT_FLAG BIT(0)
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#define GT_COMP0 0x10
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#define GT_COMP1 0x14
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#define GT_AUTO_INC 0x18
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/*
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* We are expecting to be clocked by the ARM peripheral clock.
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*
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* Note: it is assumed we are using a prescaler value of zero, so this is
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* the units for all operations.
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*/
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static void __iomem *gt_base;
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static unsigned long gt_clk_rate;
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static int gt_ppi;
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static struct clock_event_device __percpu *gt_evt;
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/*
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* To get the value from the Global Timer Counter register proceed as follows:
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* 1. Read the upper 32-bit timer counter register
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* 2. Read the lower 32-bit timer counter register
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* 3. Read the upper 32-bit timer counter register again. If the value is
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* different to the 32-bit upper value read previously, go back to step 2.
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* Otherwise the 64-bit timer counter value is correct.
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*/
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static u64 notrace _gt_counter_read(void)
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{
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u64 counter;
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u32 lower;
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u32 upper, old_upper;
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upper = readl_relaxed(gt_base + GT_COUNTER1);
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do {
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old_upper = upper;
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lower = readl_relaxed(gt_base + GT_COUNTER0);
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upper = readl_relaxed(gt_base + GT_COUNTER1);
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} while (upper != old_upper);
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counter = upper;
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counter <<= 32;
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counter |= lower;
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return counter;
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}
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static u64 gt_counter_read(void)
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{
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return _gt_counter_read();
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}
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/**
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* To ensure that updates to comparator value register do not set the
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* Interrupt Status Register proceed as follows:
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* 1. Clear the Comp Enable bit in the Timer Control Register.
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* 2. Write the lower 32-bit Comparator Value Register.
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* 3. Write the upper 32-bit Comparator Value Register.
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* 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
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*/
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static void gt_compare_set(unsigned long delta, int periodic)
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{
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u64 counter = gt_counter_read();
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unsigned long ctrl;
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counter += delta;
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ctrl = GT_CONTROL_TIMER_ENABLE;
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writel_relaxed(ctrl, gt_base + GT_CONTROL);
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writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0);
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writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1);
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if (periodic) {
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writel_relaxed(delta, gt_base + GT_AUTO_INC);
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ctrl |= GT_CONTROL_AUTO_INC;
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}
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ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
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writel_relaxed(ctrl, gt_base + GT_CONTROL);
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}
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static int gt_clockevent_shutdown(struct clock_event_device *evt)
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{
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unsigned long ctrl;
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ctrl = readl(gt_base + GT_CONTROL);
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ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
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GT_CONTROL_AUTO_INC);
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writel(ctrl, gt_base + GT_CONTROL);
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return 0;
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}
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static int gt_clockevent_set_periodic(struct clock_event_device *evt)
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{
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gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
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return 0;
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}
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static int gt_clockevent_set_next_event(unsigned long evt,
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struct clock_event_device *unused)
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{
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gt_compare_set(evt, 0);
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return 0;
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}
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static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
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{
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struct clock_event_device *evt = dev_id;
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if (!(readl_relaxed(gt_base + GT_INT_STATUS) &
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GT_INT_STATUS_EVENT_FLAG))
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return IRQ_NONE;
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/**
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* ERRATA 740657( Global Timer can send 2 interrupts for
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* the same event in single-shot mode)
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* Workaround:
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* Either disable single-shot mode.
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* Or
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* Modify the Interrupt Handler to avoid the
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* offending sequence. This is achieved by clearing
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* the Global Timer flag _after_ having incremented
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* the Comparator register value to a higher value.
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*/
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if (clockevent_state_oneshot(evt))
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gt_compare_set(ULONG_MAX, 0);
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writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS);
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evt->event_handler(evt);
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return IRQ_HANDLED;
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}
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static int gt_clockevents_init(struct clock_event_device *clk)
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{
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int cpu = smp_processor_id();
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clk->name = "arm_global_timer";
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clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
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CLOCK_EVT_FEAT_PERCPU;
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clk->set_state_shutdown = gt_clockevent_shutdown;
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clk->set_state_periodic = gt_clockevent_set_periodic;
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clk->set_state_oneshot = gt_clockevent_shutdown;
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clk->set_next_event = gt_clockevent_set_next_event;
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clk->cpumask = cpumask_of(cpu);
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clk->rating = 300;
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clk->irq = gt_ppi;
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clockevents_config_and_register(clk, gt_clk_rate,
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1, 0xffffffff);
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enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
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return 0;
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}
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static void gt_clockevents_stop(struct clock_event_device *clk)
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{
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gt_clockevent_shutdown(clk);
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disable_percpu_irq(clk->irq);
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}
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static cycle_t gt_clocksource_read(struct clocksource *cs)
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{
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return gt_counter_read();
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}
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static void gt_resume(struct clocksource *cs)
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{
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unsigned long ctrl;
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ctrl = readl(gt_base + GT_CONTROL);
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if (!(ctrl & GT_CONTROL_TIMER_ENABLE))
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/* re-enable timer on resume */
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writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
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}
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static struct clocksource gt_clocksource = {
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.name = "arm_global_timer",
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.rating = 300,
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.read = gt_clocksource_read,
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.mask = CLOCKSOURCE_MASK(64),
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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.resume = gt_resume,
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};
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#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
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static u64 notrace gt_sched_clock_read(void)
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{
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return _gt_counter_read();
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}
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#endif
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static void __init gt_clocksource_init(void)
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{
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writel(0, gt_base + GT_CONTROL);
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writel(0, gt_base + GT_COUNTER0);
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writel(0, gt_base + GT_COUNTER1);
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/* enables timer on all the cores */
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writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
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#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
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sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
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#endif
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clocksource_register_hz(>_clocksource, gt_clk_rate);
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}
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static int gt_cpu_notify(struct notifier_block *self, unsigned long action,
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void *hcpu)
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{
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switch (action & ~CPU_TASKS_FROZEN) {
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case CPU_STARTING:
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gt_clockevents_init(this_cpu_ptr(gt_evt));
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break;
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case CPU_DYING:
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gt_clockevents_stop(this_cpu_ptr(gt_evt));
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break;
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}
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return NOTIFY_OK;
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}
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static struct notifier_block gt_cpu_nb = {
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.notifier_call = gt_cpu_notify,
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};
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static void __init global_timer_of_register(struct device_node *np)
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{
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struct clk *gt_clk;
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int err = 0;
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/*
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* In A9 r2p0 the comparators for each processor with the global timer
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* fire when the timer value is greater than or equal to. In previous
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* revisions the comparators fired when the timer value was equal to.
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*/
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if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
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&& (read_cpuid_id() & 0xf0000f) < 0x200000) {
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pr_warn("global-timer: non support for this cpu version.\n");
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return;
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}
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gt_ppi = irq_of_parse_and_map(np, 0);
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if (!gt_ppi) {
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pr_warn("global-timer: unable to parse irq\n");
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return;
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}
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gt_base = of_iomap(np, 0);
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if (!gt_base) {
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pr_warn("global-timer: invalid base address\n");
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return;
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}
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gt_clk = of_clk_get(np, 0);
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if (!IS_ERR(gt_clk)) {
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err = clk_prepare_enable(gt_clk);
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if (err)
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goto out_unmap;
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} else {
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pr_warn("global-timer: clk not found\n");
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err = -EINVAL;
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goto out_unmap;
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}
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gt_clk_rate = clk_get_rate(gt_clk);
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gt_evt = alloc_percpu(struct clock_event_device);
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if (!gt_evt) {
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pr_warn("global-timer: can't allocate memory\n");
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err = -ENOMEM;
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goto out_clk;
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}
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err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
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"gt", gt_evt);
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if (err) {
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pr_warn("global-timer: can't register interrupt %d (%d)\n",
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gt_ppi, err);
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goto out_free;
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}
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err = register_cpu_notifier(>_cpu_nb);
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if (err) {
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pr_warn("global-timer: unable to register cpu notifier.\n");
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goto out_irq;
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}
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/* Immediately configure the timer on the boot CPU */
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gt_clocksource_init();
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gt_clockevents_init(this_cpu_ptr(gt_evt));
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return;
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out_irq:
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free_percpu_irq(gt_ppi, gt_evt);
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out_free:
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free_percpu(gt_evt);
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out_clk:
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clk_disable_unprepare(gt_clk);
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out_unmap:
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iounmap(gt_base);
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WARN(err, "ARM Global timer register failed (%d)\n", err);
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}
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/* Only tested on r2p2 and r3p0 */
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CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
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global_timer_of_register);
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