clocksource: apb: Share APB timer code with other platforms

The APB timers are an IP block from Synopsys (DesignWare APB timers)
and are also found in other systems including ARM SoC's.  This patch
adds functions for creating clock_event_devices and clocksources from
APB timers but does not do the resource allocation.  This is handled
in a higher layer to allow the timers to be created from multiple
methods such as platform_devices.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

3 files changed, 405 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 96c92191..141417f 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -3,3 +3,6 @@ config CLKSRC_I8253
 
 config CLKSRC_MMIO
 	bool
+
+config DW_APB_TIMER
+	bool
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index b995942..4c3d8fd 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_SH_TIMER_MTU2)	+= sh_mtu2.o
 obj-$(CONFIG_SH_TIMER_TMU)	+= sh_tmu.o
 obj-$(CONFIG_CLKSRC_I8253)	+= i8253.o
 obj-$(CONFIG_CLKSRC_MMIO)	+= mmio.o
+obj-$(CONFIG_DW_APB_TIMER)	+= dw_apb_timer.o
diff --git a/drivers/clocksource/dw_apb_timer.c b/drivers/clocksource/dw_apb_timer.c
new file mode 100644
index 0000000..580f870
--- /dev/null
+++ b/drivers/clocksource/dw_apb_timer.c
@@ -0,0 +1,401 @@
+/*
+ * (C) Copyright 2009 Intel Corporation
+ * Author: Jacob Pan (jacob.jun.pan@intel.com)
+ *
+ * Shared with ARM platforms, Jamie Iles, Picochip 2011
+ *
+ * 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.
+ *
+ * Support for the Synopsys DesignWare APB Timers.
+ */
+#include <linux/dw_apb_timer.h>
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+
+#define APBT_MIN_PERIOD			4
+#define APBT_MIN_DELTA_USEC		200
+
+#define APBTMR_N_LOAD_COUNT		0x00
+#define APBTMR_N_CURRENT_VALUE		0x04
+#define APBTMR_N_CONTROL		0x08
+#define APBTMR_N_EOI			0x0c
+#define APBTMR_N_INT_STATUS		0x10
+
+#define APBTMRS_INT_STATUS		0xa0
+#define APBTMRS_EOI			0xa4
+#define APBTMRS_RAW_INT_STATUS		0xa8
+#define APBTMRS_COMP_VERSION		0xac
+
+#define APBTMR_CONTROL_ENABLE		(1 << 0)
+/* 1: periodic, 0:free running. */
+#define APBTMR_CONTROL_MODE_PERIODIC	(1 << 1)
+#define APBTMR_CONTROL_INT		(1 << 2)
+
+static inline struct dw_apb_clock_event_device *
+ced_to_dw_apb_ced(struct clock_event_device *evt)
+{
+	return container_of(evt, struct dw_apb_clock_event_device, ced);
+}
+
+static inline struct dw_apb_clocksource *
+clocksource_to_dw_apb_clocksource(struct clocksource *cs)
+{
+	return container_of(cs, struct dw_apb_clocksource, cs);
+}
+
+static unsigned long apbt_readl(struct dw_apb_timer *timer, unsigned long offs)
+{
+	return readl(timer->base + offs);
+}
+
+static void apbt_writel(struct dw_apb_timer *timer, unsigned long val,
+		 unsigned long offs)
+{
+	writel(val, timer->base + offs);
+}
+
+static void apbt_disable_int(struct dw_apb_timer *timer)
+{
+	unsigned long ctrl = apbt_readl(timer, APBTMR_N_CONTROL);
+
+	ctrl |= APBTMR_CONTROL_INT;
+	apbt_writel(timer, ctrl, APBTMR_N_CONTROL);
+}
+
+/**
+ * dw_apb_clockevent_pause() - stop the clock_event_device from running
+ *
+ * @dw_ced:	The APB clock to stop generating events.
+ */
+void dw_apb_clockevent_pause(struct dw_apb_clock_event_device *dw_ced)
+{
+	disable_irq(dw_ced->timer.irq);
+	apbt_disable_int(&dw_ced->timer);
+}
+
+static void apbt_eoi(struct dw_apb_timer *timer)
+{
+	apbt_readl(timer, APBTMR_N_EOI);
+}
+
+static irqreturn_t dw_apb_clockevent_irq(int irq, void *data)
+{
+	struct clock_event_device *evt = data;
+	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
+
+	if (!evt->event_handler) {
+		pr_info("Spurious APBT timer interrupt %d", irq);
+		return IRQ_NONE;
+	}
+
+	if (dw_ced->eoi)
+		dw_ced->eoi(&dw_ced->timer);
+
+	evt->event_handler(evt);
+	return IRQ_HANDLED;
+}
+
+static void apbt_enable_int(struct dw_apb_timer *timer)
+{
+	unsigned long ctrl = apbt_readl(timer, APBTMR_N_CONTROL);
+	/* clear pending intr */
+	apbt_readl(timer, APBTMR_N_EOI);
+	ctrl &= ~APBTMR_CONTROL_INT;
+	apbt_writel(timer, ctrl, APBTMR_N_CONTROL);
+}
+
+static void apbt_set_mode(enum clock_event_mode mode,
+			  struct clock_event_device *evt)
+{
+	unsigned long ctrl;
+	unsigned long period;
+	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
+
+	pr_debug("%s CPU %d mode=%d\n", __func__, first_cpu(*evt->cpumask),
+		 mode);
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		period = DIV_ROUND_UP(dw_ced->timer.freq, HZ);
+		ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
+		ctrl |= APBTMR_CONTROL_MODE_PERIODIC;
+		apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+		/*
+		 * DW APB p. 46, have to disable timer before load counter,
+		 * may cause sync problem.
+		 */
+		ctrl &= ~APBTMR_CONTROL_ENABLE;
+		apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+		udelay(1);
+		pr_debug("Setting clock period %lu for HZ %d\n", period, HZ);
+		apbt_writel(&dw_ced->timer, period, APBTMR_N_LOAD_COUNT);
+		ctrl |= APBTMR_CONTROL_ENABLE;
+		apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+		break;
+
+	case CLOCK_EVT_MODE_ONESHOT:
+		ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
+		/*
+		 * set free running mode, this mode will let timer reload max
+		 * timeout which will give time (3min on 25MHz clock) to rearm
+		 * the next event, therefore emulate the one-shot mode.
+		 */
+		ctrl &= ~APBTMR_CONTROL_ENABLE;
+		ctrl &= ~APBTMR_CONTROL_MODE_PERIODIC;
+
+		apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+		/* write again to set free running mode */
+		apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+
+		/*
+		 * DW APB p. 46, load counter with all 1s before starting free
+		 * running mode.
+		 */
+		apbt_writel(&dw_ced->timer, ~0, APBTMR_N_LOAD_COUNT);
+		ctrl &= ~APBTMR_CONTROL_INT;
+		ctrl |= APBTMR_CONTROL_ENABLE;
+		apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+		break;
+
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
+		ctrl &= ~APBTMR_CONTROL_ENABLE;
+		apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+		break;
+
+	case CLOCK_EVT_MODE_RESUME:
+		apbt_enable_int(&dw_ced->timer);
+		break;
+	}
+}
+
+static int apbt_next_event(unsigned long delta,
+			   struct clock_event_device *evt)
+{
+	unsigned long ctrl;
+	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
+
+	/* Disable timer */
+	ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
+	ctrl &= ~APBTMR_CONTROL_ENABLE;
+	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+	/* write new count */
+	apbt_writel(&dw_ced->timer, delta, APBTMR_N_LOAD_COUNT);
+	ctrl |= APBTMR_CONTROL_ENABLE;
+	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
+
+	return 0;
+}
+
+/**
+ * dw_apb_clockevent_init() - use an APB timer as a clock_event_device
+ *
+ * @cpu:	The CPU the events will be targeted at.
+ * @name:	The name used for the timer and the IRQ for it.
+ * @rating:	The rating to give the timer.
+ * @base:	I/O base for the timer registers.
+ * @irq:	The interrupt number to use for the timer.
+ * @freq:	The frequency that the timer counts at.
+ *
+ * This creates a clock_event_device for using with the generic clock layer
+ * but does not start and register it.  This should be done with
+ * dw_apb_clockevent_register() as the next step.  If this is the first time
+ * it has been called for a timer then the IRQ will be requested, if not it
+ * just be enabled to allow CPU hotplug to avoid repeatedly requesting and
+ * releasing the IRQ.
+ */
+struct dw_apb_clock_event_device *
+dw_apb_clockevent_init(int cpu, const char *name, unsigned rating,
+		       void __iomem *base, int irq, unsigned long freq)
+{
+	struct dw_apb_clock_event_device *dw_ced =
+		kzalloc(sizeof(*dw_ced), GFP_KERNEL);
+	int err;
+
+	if (!dw_ced)
+		return NULL;
+
+	dw_ced->timer.base = base;
+	dw_ced->timer.irq = irq;
+	dw_ced->timer.freq = freq;
+
+	clockevents_calc_mult_shift(&dw_ced->ced, freq, APBT_MIN_PERIOD);
+	dw_ced->ced.max_delta_ns = clockevent_delta2ns(0x7fffffff,
+						       &dw_ced->ced);
+	dw_ced->ced.min_delta_ns = clockevent_delta2ns(5000, &dw_ced->ced);
+	dw_ced->ced.cpumask = cpumask_of(cpu);
+	dw_ced->ced.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
+	dw_ced->ced.set_mode = apbt_set_mode;
+	dw_ced->ced.set_next_event = apbt_next_event;
+	dw_ced->ced.irq = dw_ced->timer.irq;
+	dw_ced->ced.rating = rating;
+	dw_ced->ced.name = name;
+
+	dw_ced->irqaction.name		= dw_ced->ced.name;
+	dw_ced->irqaction.handler	= dw_apb_clockevent_irq;
+	dw_ced->irqaction.dev_id	= &dw_ced->ced;
+	dw_ced->irqaction.irq		= irq;
+	dw_ced->irqaction.flags		= IRQF_TIMER | IRQF_IRQPOLL |
+					  IRQF_NOBALANCING |
+					  IRQF_DISABLED;
+
+	dw_ced->eoi = apbt_eoi;
+	err = setup_irq(irq, &dw_ced->irqaction);
+	if (err) {
+		pr_err("failed to request timer irq\n");
+		kfree(dw_ced);
+		dw_ced = NULL;
+	}
+
+	return dw_ced;
+}
+
+/**
+ * dw_apb_clockevent_resume() - resume a clock that has been paused.
+ *
+ * @dw_ced:	The APB clock to resume.
+ */
+void dw_apb_clockevent_resume(struct dw_apb_clock_event_device *dw_ced)
+{
+	enable_irq(dw_ced->timer.irq);
+}
+
+/**
+ * dw_apb_clockevent_stop() - stop the clock_event_device and release the IRQ.
+ *
+ * @dw_ced:	The APB clock to stop generating the events.
+ */
+void dw_apb_clockevent_stop(struct dw_apb_clock_event_device *dw_ced)
+{
+	free_irq(dw_ced->timer.irq, &dw_ced->ced);
+}
+
+/**
+ * dw_apb_clockevent_register() - register the clock with the generic layer
+ *
+ * @dw_ced:	The APB clock to register as a clock_event_device.
+ */
+void dw_apb_clockevent_register(struct dw_apb_clock_event_device *dw_ced)
+{
+	apbt_writel(&dw_ced->timer, 0, APBTMR_N_CONTROL);
+	clockevents_register_device(&dw_ced->ced);
+	apbt_enable_int(&dw_ced->timer);
+}
+
+/**
+ * dw_apb_clocksource_start() - start the clocksource counting.
+ *
+ * @dw_cs:	The clocksource to start.
+ *
+ * This is used to start the clocksource before registration and can be used
+ * to enable calibration of timers.
+ */
+void dw_apb_clocksource_start(struct dw_apb_clocksource *dw_cs)
+{
+	/*
+	 * start count down from 0xffff_ffff. this is done by toggling the
+	 * enable bit then load initial load count to ~0.
+	 */
+	unsigned long ctrl = apbt_readl(&dw_cs->timer, APBTMR_N_CONTROL);
+
+	ctrl &= ~APBTMR_CONTROL_ENABLE;
+	apbt_writel(&dw_cs->timer, ctrl, APBTMR_N_CONTROL);
+	apbt_writel(&dw_cs->timer, ~0, APBTMR_N_LOAD_COUNT);
+	/* enable, mask interrupt */
+	ctrl &= ~APBTMR_CONTROL_MODE_PERIODIC;
+	ctrl |= (APBTMR_CONTROL_ENABLE | APBTMR_CONTROL_INT);
+	apbt_writel(&dw_cs->timer, ctrl, APBTMR_N_CONTROL);
+	/* read it once to get cached counter value initialized */
+	dw_apb_clocksource_read(dw_cs);
+}
+
+static cycle_t __apbt_read_clocksource(struct clocksource *cs)
+{
+	unsigned long current_count;
+	struct dw_apb_clocksource *dw_cs =
+		clocksource_to_dw_apb_clocksource(cs);
+
+	current_count = apbt_readl(&dw_cs->timer, APBTMR_N_CURRENT_VALUE);
+
+	return (cycle_t)~current_count;
+}
+
+static void apbt_restart_clocksource(struct clocksource *cs)
+{
+	struct dw_apb_clocksource *dw_cs =
+		clocksource_to_dw_apb_clocksource(cs);
+
+	dw_apb_clocksource_start(dw_cs);
+}
+
+/**
+ * dw_apb_clocksource_init() - use an APB timer as a clocksource.
+ *
+ * @rating:	The rating to give the clocksource.
+ * @name:	The name for the clocksource.
+ * @base:	The I/O base for the timer registers.
+ * @freq:	The frequency that the timer counts at.
+ *
+ * This creates a clocksource using an APB timer but does not yet register it
+ * with the clocksource system.  This should be done with
+ * dw_apb_clocksource_register() as the next step.
+ */
+struct dw_apb_clocksource *
+dw_apb_clocksource_init(unsigned rating, char *name, void __iomem *base,
+			unsigned long freq)
+{
+	struct dw_apb_clocksource *dw_cs = kzalloc(sizeof(*dw_cs), GFP_KERNEL);
+
+	if (!dw_cs)
+		return NULL;
+
+	dw_cs->timer.base = base;
+	dw_cs->timer.freq = freq;
+	dw_cs->cs.name = name;
+	dw_cs->cs.rating = rating;
+	dw_cs->cs.read = __apbt_read_clocksource;
+	dw_cs->cs.mask = CLOCKSOURCE_MASK(32);
+	dw_cs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+	dw_cs->cs.resume = apbt_restart_clocksource;
+
+	return dw_cs;
+}
+
+/**
+ * dw_apb_clocksource_register() - register the APB clocksource.
+ *
+ * @dw_cs:	The clocksource to register.
+ */
+void dw_apb_clocksource_register(struct dw_apb_clocksource *dw_cs)
+{
+	clocksource_register_hz(&dw_cs->cs, dw_cs->timer.freq);
+}
+
+/**
+ * dw_apb_clocksource_read() - read the current value of a clocksource.
+ *
+ * @dw_cs:	The clocksource to read.
+ */
+cycle_t dw_apb_clocksource_read(struct dw_apb_clocksource *dw_cs)
+{
+	return (cycle_t)~apbt_readl(&dw_cs->timer, APBTMR_N_CURRENT_VALUE);
+}
+
+/**
+ * dw_apb_clocksource_unregister() - unregister and free a clocksource.
+ *
+ * @dw_cs:	The clocksource to unregister/free.
+ */
+void dw_apb_clocksource_unregister(struct dw_apb_clocksource *dw_cs)
+{
+	clocksource_unregister(&dw_cs->cs);
+
+	kfree(dw_cs);
+}