ARM: clocksource: Add support for MOXA ART SoCs

This patch adds an clocksource driver for the main timer(s)
found on MOXA ART SoCs.

The MOXA ART SoC provides three separate timers with individual
count/load/match registers, two are used here:

TIMER1: clockevents, used to support oneshot and periodic events
TIMER2: set up as a free running counter, used as clocksource

Timers are preconfigured by bootloader to count down and interrupt
on match or zero. Count increments every APB clock cycle and is
automatically reloaded when it reaches zero.
Signed-off-by: Jonas Jensen <jonas.jensen@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

Documentation/devicetree/bindings/timer/moxa,moxart-timer.txt

+MOXA ART timer
+
+Required properties:
+
+- compatible : Should be "moxa,moxart-timer"
+- reg : Should contain registers location and length
+- interrupts : Should contain the timer interrupt number
+- clocks : Should contain phandle for APB clock "clkapb"
+
+Example:
+
+	timer: timer@98400000 {
+		compatible = "moxa,moxart-timer";
+		reg = <0x98400000 0x42>;
+		interrupts = <19 1>;
+		clocks = <&clkapb>;
+	};

drivers/clocksource/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_ARMADA_370_XP_TIMER)	+= time-armada-370-xp.o
 obj-$(CONFIG_ORION_TIMER)	+= time-orion.o
 obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835_timer.o
 obj-$(CONFIG_ARCH_MARCO)	+= timer-marco.o
+obj-$(CONFIG_ARCH_MOXART)	+= moxart_timer.o
 obj-$(CONFIG_ARCH_MXS)		+= mxs_timer.o
 obj-$(CONFIG_ARCH_PRIMA2)	+= timer-prima2.o
 obj-$(CONFIG_SUN4I_TIMER)	+= sun4i_timer.o

drivers/clocksource/moxart_timer.c

+/*
+ * MOXA ART SoCs timer handling.
+ *
+ * Copyright (C) 2013 Jonas Jensen
+ *
+ * Jonas Jensen <jonas.jensen@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqreturn.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/io.h>
+#include <linux/clocksource.h>
+
+#define TIMER1_BASE		0x00
+#define TIMER2_BASE		0x10
+#define TIMER3_BASE		0x20
+
+#define REG_COUNT		0x0 /* writable */
+#define REG_LOAD		0x4
+#define REG_MATCH1		0x8
+#define REG_MATCH2		0xC
+
+#define TIMER_CR		0x30
+#define TIMER_INTR_STATE	0x34
+#define TIMER_INTR_MASK		0x38
+
+/*
+ * TIMER_CR flags:
+ *
+ * TIMEREG_CR_*_CLOCK	0: PCLK, 1: EXT1CLK
+ * TIMEREG_CR_*_INT	overflow interrupt enable bit
+ */
+#define TIMEREG_CR_1_ENABLE	BIT(0)
+#define TIMEREG_CR_1_CLOCK	BIT(1)
+#define TIMEREG_CR_1_INT	BIT(2)
+#define TIMEREG_CR_2_ENABLE	BIT(3)
+#define TIMEREG_CR_2_CLOCK	BIT(4)
+#define TIMEREG_CR_2_INT	BIT(5)
+#define TIMEREG_CR_3_ENABLE	BIT(6)
+#define TIMEREG_CR_3_CLOCK	BIT(7)
+#define TIMEREG_CR_3_INT	BIT(8)
+#define TIMEREG_CR_COUNT_UP	BIT(9)
+
+#define TIMER1_ENABLE		(TIMEREG_CR_2_ENABLE | TIMEREG_CR_1_ENABLE)
+#define TIMER1_DISABLE		(TIMEREG_CR_2_ENABLE)
+
+static void __iomem *base;
+static unsigned int clock_count_per_tick;
+
+static void moxart_clkevt_mode(enum clock_event_mode mode,
+			       struct clock_event_device *clk)
+{
+	switch (mode) {
+	case CLOCK_EVT_MODE_RESUME:
+	case CLOCK_EVT_MODE_ONESHOT:
+		writel(TIMER1_DISABLE, base + TIMER_CR);
+		writel(~0, base + TIMER1_BASE + REG_LOAD);
+		break;
+	case CLOCK_EVT_MODE_PERIODIC:
+		writel(clock_count_per_tick, base + TIMER1_BASE + REG_LOAD);
+		writel(TIMER1_ENABLE, base + TIMER_CR);
+		break;
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	default:
+		writel(TIMER1_DISABLE, base + TIMER_CR);
+		break;
+	}
+}
+
+static int moxart_clkevt_next_event(unsigned long cycles,
+				    struct clock_event_device *unused)
+{
+	u32 u;
+
+	writel(TIMER1_DISABLE, base + TIMER_CR);
+
+	u = readl(base + TIMER1_BASE + REG_COUNT) - cycles;
+	writel(u, base + TIMER1_BASE + REG_MATCH1);
+
+	writel(TIMER1_ENABLE, base + TIMER_CR);
+
+	return 0;
+}
+
+static struct clock_event_device moxart_clockevent = {
+	.name		= "moxart_timer",
+	.rating		= 200,
+	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+	.set_mode	= moxart_clkevt_mode,
+	.set_next_event	= moxart_clkevt_next_event,
+};
+
+static irqreturn_t moxart_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+	evt->event_handler(evt);
+	return IRQ_HANDLED;
+}
+
+static struct irqaction moxart_timer_irq = {
+	.name		= "moxart-timer",
+	.flags		= IRQF_TIMER,
+	.handler	= moxart_timer_interrupt,
+	.dev_id		= &moxart_clockevent,
+};
+
+static void __init moxart_timer_init(struct device_node *node)
+{
+	int ret, irq;
+	unsigned long pclk;
+	struct clk *clk;
+
+	base = of_iomap(node, 0);
+	if (!base)
+		panic("%s: of_iomap failed\n", node->full_name);
+
+	irq = irq_of_parse_and_map(node, 0);
+	if (irq <= 0)
+		panic("%s: irq_of_parse_and_map failed\n", node->full_name);
+
+	ret = setup_irq(irq, &moxart_timer_irq);
+	if (ret)
+		panic("%s: setup_irq failed\n", node->full_name);
+
+	clk = of_clk_get(node, 0);
+	if (IS_ERR(clk))
+		panic("%s: of_clk_get failed\n", node->full_name);
+
+	pclk = clk_get_rate(clk);
+
+	if (clocksource_mmio_init(base + TIMER2_BASE + REG_COUNT,
+				  "moxart_timer", pclk, 200, 32,
+				  clocksource_mmio_readl_down))
+		panic("%s: clocksource_mmio_init failed\n", node->full_name);
+
+	clock_count_per_tick = DIV_ROUND_CLOSEST(pclk, HZ);
+
+	writel(~0, base + TIMER2_BASE + REG_LOAD);
+	writel(TIMEREG_CR_2_ENABLE, base + TIMER_CR);
+
+	moxart_clockevent.cpumask = cpumask_of(0);
+	moxart_clockevent.irq = irq;
+
+	/*
+	 * documentation is not publicly available:
+	 * min_delta / max_delta obtained by trial-and-error,
+	 * max_delta 0xfffffffe should be ok because count
+	 * register size is u32
+	 */
+	clockevents_config_and_register(&moxart_clockevent, pclk,
+					0x4, 0xfffffffe);
+}
+CLOCKSOURCE_OF_DECLARE(moxart, "moxa,moxart-timer", moxart_timer_init);