1 files changed, 442 insertions, 0 deletions
diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c
new file mode 100644
index 0000000000..44a61dc6f9
--- /dev/null
+++ b/drivers/clocksource/arm_global_timer.c
@@ -0,0 +1,442 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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>
+ */
+
+#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/delay.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_CONTROL_PRESCALER_SHIFT      8
+#define GT_CONTROL_PRESCALER_MAX        0xF
+#define GT_CONTROL_PRESCALER_MASK       (GT_CONTROL_PRESCALER_MAX << \
+					 GT_CONTROL_PRESCALER_SHIFT)
+
+#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
+
+#define MAX_F_ERR 50
+/*
+ * 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 struct notifier_block gt_clk_rate_change_nb;
+static u32 gt_psv_new, gt_psv_bck, gt_target_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 notrace _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;
+}
+
+static u64 gt_counter_read(void)
+{
+	return _gt_counter_read();
+}
+
+/**
+ * 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 = readl(gt_base + GT_CONTROL);
+	ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE |
+		  GT_CONTROL_AUTO_INC);
+	ctrl |= GT_CONTROL_TIMER_ENABLE;
+	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);
+
+	if (periodic) {
+		writel_relaxed(delta, gt_base + GT_AUTO_INC);
+		ctrl |= GT_CONTROL_AUTO_INC;
+	}
+
+	ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
+	writel_relaxed(ctrl, gt_base + GT_CONTROL);
+}
+
+static int gt_clockevent_shutdown(struct clock_event_device *evt)
+{
+	unsigned long ctrl;
+
+	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_target_rate, HZ), 1);
+	return 0;
+}
+
+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 (clockevent_state_oneshot(evt))
+		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_starting_cpu(unsigned int cpu)
+{
+	struct clock_event_device *clk = this_cpu_ptr(gt_evt);
+
+	clk->name = "arm_global_timer";
+	clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
+		CLOCK_EVT_FEAT_PERCPU;
+	clk->set_state_shutdown = gt_clockevent_shutdown;
+	clk->set_state_periodic = gt_clockevent_set_periodic;
+	clk->set_state_oneshot = gt_clockevent_shutdown;
+	clk->set_state_oneshot_stopped = gt_clockevent_shutdown;
+	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_target_rate,
+					1, 0xffffffff);
+	enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
+	return 0;
+}
+
+static int gt_dying_cpu(unsigned int cpu)
+{
+	struct clock_event_device *clk = this_cpu_ptr(gt_evt);
+
+	gt_clockevent_shutdown(clk);
+	disable_percpu_irq(clk->irq);
+	return 0;
+}
+
+static u64 gt_clocksource_read(struct clocksource *cs)
+{
+	return gt_counter_read();
+}
+
+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);
+}
+
+static struct clocksource gt_clocksource = {
+	.name	= "arm_global_timer",
+	.rating	= 300,
+	.read	= gt_clocksource_read,
+	.mask	= CLOCKSOURCE_MASK(64),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.resume = gt_resume,
+};
+
+#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
+static u64 notrace gt_sched_clock_read(void)
+{
+	return _gt_counter_read();
+}
+#endif
+
+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 gt_write_presc(u32 psv)
+{
+	u32 reg;
+
+	reg = readl(gt_base + GT_CONTROL);
+	reg &= ~GT_CONTROL_PRESCALER_MASK;
+	reg |= psv << GT_CONTROL_PRESCALER_SHIFT;
+	writel(reg, gt_base + GT_CONTROL);
+}
+
+static u32 gt_read_presc(void)
+{
+	u32 reg;
+
+	reg = readl(gt_base + GT_CONTROL);
+	reg &= GT_CONTROL_PRESCALER_MASK;
+	return reg >> GT_CONTROL_PRESCALER_SHIFT;
+}
+
+static void __init gt_delay_timer_init(void)
+{
+	gt_delay_timer.freq = gt_target_rate;
+	register_current_timer_delay(&gt_delay_timer);
+}
+
+static int __init gt_clocksource_init(void)
+{
+	writel(0, gt_base + GT_CONTROL);
+	writel(0, gt_base + GT_COUNTER0);
+	writel(0, gt_base + GT_COUNTER1);
+	/* set prescaler and enable timer on all the cores */
+	writel(((CONFIG_ARM_GT_INITIAL_PRESCALER_VAL - 1) <<
+		GT_CONTROL_PRESCALER_SHIFT)
+	       | 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_target_rate);
+#endif
+	return clocksource_register_hz(&gt_clocksource, gt_target_rate);
+}
+
+static int gt_clk_rate_change_cb(struct notifier_block *nb,
+				 unsigned long event, void *data)
+{
+	struct clk_notifier_data *ndata = data;
+
+	switch (event) {
+	case PRE_RATE_CHANGE:
+	{
+		int psv;
+
+		psv = DIV_ROUND_CLOSEST(ndata->new_rate,
+					gt_target_rate);
+
+		if (abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR)
+			return NOTIFY_BAD;
+
+		psv--;
+
+		/* prescaler within legal range? */
+		if (psv < 0 || psv > GT_CONTROL_PRESCALER_MAX)
+			return NOTIFY_BAD;
+
+		/*
+		 * store timer clock ctrl register so we can restore it in case
+		 * of an abort.
+		 */
+		gt_psv_bck = gt_read_presc();
+		gt_psv_new = psv;
+		/* scale down: adjust divider in post-change notification */
+		if (ndata->new_rate < ndata->old_rate)
+			return NOTIFY_DONE;
+
+		/* scale up: adjust divider now - before frequency change */
+		gt_write_presc(psv);
+		break;
+	}
+	case POST_RATE_CHANGE:
+		/* scale up: pre-change notification did the adjustment */
+		if (ndata->new_rate > ndata->old_rate)
+			return NOTIFY_OK;
+
+		/* scale down: adjust divider now - after frequency change */
+		gt_write_presc(gt_psv_new);
+		break;
+
+	case ABORT_RATE_CHANGE:
+		/* we have to undo the adjustment in case we scale up */
+		if (ndata->new_rate < ndata->old_rate)
+			return NOTIFY_OK;
+
+		/* restore original register value */
+		gt_write_presc(gt_psv_bck);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int __init global_timer_of_register(struct device_node *np)
+{
+	struct clk *gt_clk;
+	static unsigned long gt_clk_rate;
+	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 -ENOSYS;
+	}
+
+	gt_ppi = irq_of_parse_and_map(np, 0);
+	if (!gt_ppi) {
+		pr_warn("global-timer: unable to parse irq\n");
+		return -EINVAL;
+	}
+
+	gt_base = of_iomap(np, 0);
+	if (!gt_base) {
+		pr_warn("global-timer: invalid base address\n");
+		return -ENXIO;
+	}
+
+	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_target_rate = gt_clk_rate / CONFIG_ARM_GT_INITIAL_PRESCALER_VAL;
+	gt_clk_rate_change_nb.notifier_call =
+		gt_clk_rate_change_cb;
+	err = clk_notifier_register(gt_clk, &gt_clk_rate_change_nb);
+	if (err) {
+		pr_warn("Unable to register clock notifier\n");
+		goto out_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_nb;
+	}
+
+	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;
+	}
+
+	/* Register and immediately configure the timer on the boot CPU */
+	err = gt_clocksource_init();
+	if (err)
+		goto out_irq;
+	
+	err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
+				"clockevents/arm/global_timer:starting",
+				gt_starting_cpu, gt_dying_cpu);
+	if (err)
+		goto out_irq;
+
+	gt_delay_timer_init();
+
+	return 0;
+
+out_irq:
+	free_percpu_irq(gt_ppi, gt_evt);
+out_free:
+	free_percpu(gt_evt);
+out_clk_nb:
+	clk_notifier_unregister(gt_clk, &gt_clk_rate_change_nb);
+out_clk:
+	clk_disable_unprepare(gt_clk);
+out_unmap:
+	iounmap(gt_base);
+	WARN(err, "ARM Global timer register failed (%d)\n", err);
+
+	return err;
+}
+
+/* Only tested on r2p2 and r3p0  */
+TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
+			global_timer_of_register);