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drivers/clocksource/arm_global_timer.c
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/* * drivers/clocksource/arm_global_timer.c * * Copyright (C) 2013 STMicroelectronics (R&D) Limited. * Author: Stuart Menefy <stuart.menefy@st.com> * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include <linux/init.h> #include <linux/interrupt.h> #include <linux/clocksource.h> #include <linux/clockchips.h> #include <linux/cpu.h> #include <linux/clk.h> |
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#include <linux/delay.h> |
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#include <linux/err.h> #include <linux/io.h> #include <linux/of.h> #include <linux/of_irq.h> #include <linux/of_address.h> #include <linux/sched_clock.h> #include <asm/cputype.h> #define GT_COUNTER0 0x00 #define GT_COUNTER1 0x04 #define GT_CONTROL 0x08 #define GT_CONTROL_TIMER_ENABLE BIT(0) /* this bit is NOT banked */ #define GT_CONTROL_COMP_ENABLE BIT(1) /* banked */ #define GT_CONTROL_IRQ_ENABLE BIT(2) /* banked */ #define GT_CONTROL_AUTO_INC BIT(3) /* banked */ #define GT_INT_STATUS 0x0c #define GT_INT_STATUS_EVENT_FLAG BIT(0) #define GT_COMP0 0x10 #define GT_COMP1 0x14 #define GT_AUTO_INC 0x18 /* * We are expecting to be clocked by the ARM peripheral clock. * * Note: it is assumed we are using a prescaler value of zero, so this is * the units for all operations. */ static void __iomem *gt_base; static unsigned long gt_clk_rate; static int gt_ppi; static struct clock_event_device __percpu *gt_evt; /* * To get the value from the Global Timer Counter register proceed as follows: * 1. Read the upper 32-bit timer counter register * 2. Read the lower 32-bit timer counter register * 3. Read the upper 32-bit timer counter register again. If the value is * different to the 32-bit upper value read previously, go back to step 2. * Otherwise the 64-bit timer counter value is correct. */ |
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static u64 notrace _gt_counter_read(void) |
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{ u64 counter; u32 lower; u32 upper, old_upper; upper = readl_relaxed(gt_base + GT_COUNTER1); do { old_upper = upper; lower = readl_relaxed(gt_base + GT_COUNTER0); upper = readl_relaxed(gt_base + GT_COUNTER1); } while (upper != old_upper); counter = upper; counter <<= 32; counter |= lower; return counter; } |
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static u64 gt_counter_read(void) { return _gt_counter_read(); } |
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/** * To ensure that updates to comparator value register do not set the * Interrupt Status Register proceed as follows: * 1. Clear the Comp Enable bit in the Timer Control Register. * 2. Write the lower 32-bit Comparator Value Register. * 3. Write the upper 32-bit Comparator Value Register. * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit. */ static void gt_compare_set(unsigned long delta, int periodic) { u64 counter = gt_counter_read(); unsigned long ctrl; counter += delta; ctrl = GT_CONTROL_TIMER_ENABLE; |
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writel_relaxed(ctrl, gt_base + GT_CONTROL); writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0); 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; } 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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{ unsigned long ctrl; |
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ctrl = readl(gt_base + GT_CONTROL); ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE | GT_CONTROL_AUTO_INC); writel(ctrl, gt_base + GT_CONTROL); return 0; } static int gt_clockevent_set_periodic(struct clock_event_device *evt) { gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1); return 0; |
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} static int gt_clockevent_set_next_event(unsigned long evt, struct clock_event_device *unused) { gt_compare_set(evt, 0); return 0; } static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id) { struct clock_event_device *evt = dev_id; if (!(readl_relaxed(gt_base + GT_INT_STATUS) & GT_INT_STATUS_EVENT_FLAG)) return IRQ_NONE; /** * ERRATA 740657( Global Timer can send 2 interrupts for * the same event in single-shot mode) * Workaround: * Either disable single-shot mode. * Or * Modify the Interrupt Handler to avoid the * offending sequence. This is achieved by clearing * the Global Timer flag _after_ having incremented * the Comparator register value to a higher value. */ |
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if (clockevent_state_oneshot(evt)) |
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gt_compare_set(ULONG_MAX, 0); writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS); evt->event_handler(evt); return IRQ_HANDLED; } |
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static int gt_starting_cpu(unsigned int cpu) |
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{ |
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struct clock_event_device *clk = this_cpu_ptr(gt_evt); |
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clk->name = "arm_global_timer"; |
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clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERCPU; |
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clk->set_state_shutdown = gt_clockevent_shutdown; clk->set_state_periodic = gt_clockevent_set_periodic; clk->set_state_oneshot = gt_clockevent_shutdown; |
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clk->set_state_oneshot_stopped = gt_clockevent_shutdown; |
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clk->set_next_event = gt_clockevent_set_next_event; clk->cpumask = cpumask_of(cpu); clk->rating = 300; clk->irq = gt_ppi; clockevents_config_and_register(clk, gt_clk_rate, 1, 0xffffffff); enable_percpu_irq(clk->irq, IRQ_TYPE_NONE); return 0; } |
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static int gt_dying_cpu(unsigned int cpu) |
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{ |
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struct clock_event_device *clk = this_cpu_ptr(gt_evt); |
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gt_clockevent_shutdown(clk); |
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disable_percpu_irq(clk->irq); |
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return 0; |
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} static cycle_t gt_clocksource_read(struct clocksource *cs) { return gt_counter_read(); } |
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static void gt_resume(struct clocksource *cs) { unsigned long ctrl; ctrl = readl(gt_base + GT_CONTROL); if (!(ctrl & GT_CONTROL_TIMER_ENABLE)) /* re-enable timer on resume */ writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); } |
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static struct clocksource gt_clocksource = { .name = "arm_global_timer", .rating = 300, .read = gt_clocksource_read, .mask = CLOCKSOURCE_MASK(64), .flags = CLOCK_SOURCE_IS_CONTINUOUS, |
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.resume = gt_resume, |
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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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} #endif |
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static unsigned long gt_read_long(void) { return readl_relaxed(gt_base + GT_COUNTER0); } static struct delay_timer gt_delay_timer = { .read_current_timer = gt_read_long, }; static void __init gt_delay_timer_init(void) { gt_delay_timer.freq = gt_clk_rate; register_current_timer_delay(>_delay_timer); } |
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static int __init gt_clocksource_init(void) |
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{ writel(0, gt_base + GT_CONTROL); writel(0, gt_base + GT_COUNTER0); writel(0, gt_base + GT_COUNTER1); /* enables timer on all the cores */ writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); #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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return clocksource_register_hz(>_clocksource, gt_clk_rate); |
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} |
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static int __init global_timer_of_register(struct device_node *np) |
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{ struct clk *gt_clk; int err = 0; /* |
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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 * revisions the comparators fired when the timer value was equal to. */ |
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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. "); |
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return -ENOSYS; |
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} gt_ppi = irq_of_parse_and_map(np, 0); if (!gt_ppi) { pr_warn("global-timer: unable to parse irq "); |
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return -EINVAL; |
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} gt_base = of_iomap(np, 0); if (!gt_base) { pr_warn("global-timer: invalid base address "); |
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return -ENXIO; |
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} gt_clk = of_clk_get(np, 0); if (!IS_ERR(gt_clk)) { err = clk_prepare_enable(gt_clk); if (err) goto out_unmap; } else { pr_warn("global-timer: clk not found "); err = -EINVAL; goto out_unmap; } gt_clk_rate = clk_get_rate(gt_clk); gt_evt = alloc_percpu(struct clock_event_device); if (!gt_evt) { pr_warn("global-timer: can't allocate memory "); err = -ENOMEM; goto out_clk; } err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt, "gt", gt_evt); if (err) { pr_warn("global-timer: can't register interrupt %d (%d) ", gt_ppi, err); goto out_free; } |
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/* Register and immediately configure the timer on the boot CPU */ |
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err = gt_clocksource_init(); if (err) goto out_irq; |
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err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING, "AP_ARM_GLOBAL_TIMER_STARTING", gt_starting_cpu, gt_dying_cpu); |
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if (err) goto out_irq; |
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gt_delay_timer_init(); |
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|
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return 0; |
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out_irq: free_percpu_irq(gt_ppi, gt_evt); out_free: free_percpu(gt_evt); out_clk: clk_disable_unprepare(gt_clk); out_unmap: iounmap(gt_base); WARN(err, "ARM Global timer register failed (%d) ", err); |
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return err; |
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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); |