--- /dev/null
+/*
+ * 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>
+#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.
+ */
+static u64 gt_counter_read(void)
+{
+ 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;
+}
+
+/**
+ * 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;
+ writel(ctrl, gt_base + GT_CONTROL);
+ writel(lower_32_bits(counter), gt_base + GT_COMP0);
+ writel(upper_32_bits(counter), gt_base + GT_COMP1);
+
+ if (periodic) {
+ writel(delta, gt_base + GT_AUTO_INC);
+ ctrl |= GT_CONTROL_AUTO_INC;
+ }
+
+ ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
+ writel(ctrl, gt_base + GT_CONTROL);
+}
+
+static void gt_clockevent_set_mode(enum clock_event_mode mode,
+ struct clock_event_device *clk)
+{
+ unsigned long ctrl;
+
+ switch (mode) {
+ case CLOCK_EVT_MODE_PERIODIC:
+ gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
+ break;
+ case CLOCK_EVT_MODE_ONESHOT:
+ case CLOCK_EVT_MODE_UNUSED:
+ case CLOCK_EVT_MODE_SHUTDOWN:
+ 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);
+ break;
+ default:
+ break;
+ }
+}
+
+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.
+ */
+ if (evt->mode == CLOCK_EVT_MODE_ONESHOT)
+ 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;
+}
+
+static int gt_clockevents_init(struct clock_event_device *clk)
+{
+ int cpu = smp_processor_id();
+
+ clk->name = "arm_global_timer";
+ clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
+ CLOCK_EVT_FEAT_PERCPU;
+ clk->set_mode = gt_clockevent_set_mode;
+ 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;
+}
+
+static void gt_clockevents_stop(struct clock_event_device *clk)
+{
+ gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
+ disable_percpu_irq(clk->irq);
+}
+
+static cycle_t gt_clocksource_read(struct clocksource *cs)
+{
+ return gt_counter_read();
+}
+
+static struct clocksource gt_clocksource = {
+ .name = "arm_global_timer",
+ .rating = 300,
+ .read = gt_clocksource_read,
+ .mask = CLOCKSOURCE_MASK(64),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
+static u64 notrace gt_sched_clock_read(void)
+{
+ return gt_counter_read();
+}
+#endif
+
+static void __init gt_clocksource_init(void)
+{
+ 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
+ sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
+#endif
+ clocksource_register_hz(>_clocksource, gt_clk_rate);
+}
+
+static int gt_cpu_notify(struct notifier_block *self, unsigned long action,
+ void *hcpu)
+{
+ switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_STARTING:
+ gt_clockevents_init(this_cpu_ptr(gt_evt));
+ break;
+ case CPU_DYING:
+ gt_clockevents_stop(this_cpu_ptr(gt_evt));
+ break;
+ }
+
+ return NOTIFY_OK;
+}
+static struct notifier_block gt_cpu_nb = {
+ .notifier_call = gt_cpu_notify,
+};
+
+static void __init global_timer_of_register(struct device_node *np)
+{
+ struct clk *gt_clk;
+ int err = 0;
+
+ /*
+ * In A9 r2p0 the comparators for each processor with the global timer
+ * fire when the timer value is greater than or equal to. In previous
+ * revisions the comparators fired when the timer value was equal to.
+ */
+ if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9
+ && (read_cpuid_id() & 0xf0000f) < 0x200000) {
+ pr_warn("global-timer: non support for this cpu version.\n");
+ return;
+ }
+
+ gt_ppi = irq_of_parse_and_map(np, 0);
+ if (!gt_ppi) {
+ pr_warn("global-timer: unable to parse irq\n");
+ return;
+ }
+
+ gt_base = of_iomap(np, 0);
+ if (!gt_base) {
+ pr_warn("global-timer: invalid base address\n");
+ return;
+ }
+
+ 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\n");
+ 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\n");
+ 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)\n",
+ gt_ppi, err);
+ goto out_free;
+ }
+
+ err = register_cpu_notifier(>_cpu_nb);
+ if (err) {
+ pr_warn("global-timer: unable to register cpu notifier.\n");
+ goto out_irq;
+ }
+
+ /* Immediately configure the timer on the boot CPU */
+ gt_clocksource_init();
+ gt_clockevents_init(this_cpu_ptr(gt_evt));
+
+ return;
+
+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)\n", err);
+}
+
+/* Only tested on r2p2 and r3p0 */
+CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
+ global_timer_of_register);
Code Review / kvmfornfv.git / blobdiff