![Stuart Menefy](/assets/img/avatar_default.png)
This is a simple driver for the global timer module found in the Cortex A9-MP cores from revision r1p0 onwards. This should be able to perform the functions of the system timer and the local timer in an SMP system. The global timer has the following features: The global timer is a 64-bit incrementing counter with an auto-incrementing feature. It continues incrementing after sending interrupts. The global timer is memory mapped in the private memory region. The global timer is accessible to all Cortex-A9 processors in the cluster. Each Cortex-A9 processor has a private 64-bit comparator that is used to assert a private interrupt when the global timer has reached the comparator value. All the Cortex-A9 processors in a design use the banked ID, ID27, for this interrupt. ID27 is sent to the Interrupt Controller as a Private Peripheral Interrupt. The global timer is clocked by PERIPHCLK. Signed-off-by: Stuart Menefy <stuart.menefy@st.com> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com> CC: Arnd Bergmann <arnd@arndb.de> CC: Rob Herring <robherring2@gmail.com> CC: Linus Walleij <linus.walleij@linaro.org> CC: Will Deacon <will.deacon@arm.com> CC: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
322 lines
8.2 KiB
C
322 lines
8.2 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 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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/**
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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(ctrl, gt_base + GT_CONTROL);
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writel(lower_32_bits(counter), gt_base + GT_COMP0);
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writel(upper_32_bits(counter), gt_base + GT_COMP1);
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if (periodic) {
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writel(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(ctrl, gt_base + GT_CONTROL);
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}
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static void gt_clockevent_set_mode(enum clock_event_mode mode,
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struct clock_event_device *clk)
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{
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unsigned long ctrl;
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switch (mode) {
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case CLOCK_EVT_MODE_PERIODIC:
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gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
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break;
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case CLOCK_EVT_MODE_ONESHOT:
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case CLOCK_EVT_MODE_UNUSED:
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case CLOCK_EVT_MODE_SHUTDOWN:
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ctrl = readl(gt_base + GT_CONTROL);
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ctrl &= ~(GT_CONTROL_COMP_ENABLE |
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GT_CONTROL_IRQ_ENABLE | GT_CONTROL_AUTO_INC);
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writel(ctrl, gt_base + GT_CONTROL);
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break;
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default:
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break;
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}
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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 (evt->mode == CLOCK_EVT_MODE_ONESHOT)
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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 __cpuinit 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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clk->set_mode = gt_clockevent_set_mode;
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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_set_mode(CLOCK_EVT_MODE_UNUSED, 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 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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};
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#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
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static u32 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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setup_sched_clock(gt_sched_clock_read, 32, 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 __cpuinit gt_cpu_notify(struct notifier_block *self,
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unsigned long action, 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 __cpuinitdata = {
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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 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_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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