[PATCH v3] ARM: clocksource: add support for MOXA ART SoCs

[jonas.jensen@gmail.com (Jonas Jensen)]

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

Signed-off-by: Jonas Jensen <jonas.jensen@gmail.com>
---

Notes:
    Applies to next-20130619
    
    Changes since v2:
    
    1. remove unused defines: MAX_TIMER, USED_TIMER, APB_CLK
    2. split register defines so each timer has a base
    3. use standard multiline comments
    4. replace whitespaces with tabs
    5. rename "timer_base" "base"
    6. rename "clock_frequency" "clock_count_per_tick"
    7. disable TIMER1 in CLOCK_EVT_MODE_ONESHOT
    8. remove pr_debug:s
    9. in CLOCK_EVT_MODE_PERIODIC, switch order, write clock_count_per_tick
       to TIMER1 LOAD and enable it
    10. enable TIMER1 in moxart_clkevt_next_event
    11. remove IRQF_DISABLED, IRQF_IRQPOLL from irqaction flags
    12. set clock_frequency exclusively from system clock
    13. bail if of_clk_get fails
    14. assign clock_count_per_tick to DIV_ROUND_CLOSEST(pclk, HZ)
    15. align continuation lines with matching opening brace

 drivers/clocksource/Makefile       |   1 +
 drivers/clocksource/moxart_timer.c | 166 +++++++++++++++++++++++++++++++++++++
 2 files changed, 167 insertions(+)
 create mode 100644 drivers/clocksource/moxart_timer.c

diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 8d979c7..c93e1a8 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -29,3 +29,4 @@ obj-$(CONFIG_CLKSRC_SAMSUNG_PWM)	+= samsung_pwm_timer.o
 
 obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
 obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o
+obj-$(CONFIG_ARCH_MOXART)	+= moxart_timer.o
diff --git a/drivers/clocksource/moxart_timer.c b/drivers/clocksource/moxart_timer.c
new file mode 100644
index 0000000..4678b30
--- /dev/null
+++ b/drivers/clocksource/moxart_timer.c
@@ -0,0 +1,166 @@
+/*
+ * 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		(1 << 0)
+#define TIMEREG_CR_1_CLOCK		(1 << 1)
+#define TIMEREG_CR_1_INT		(1 << 2)
+#define TIMEREG_CR_2_ENABLE		(1 << 3)
+#define TIMEREG_CR_2_CLOCK		(1 << 4)
+#define TIMEREG_CR_2_INT		(1 << 5)
+#define TIMEREG_CR_3_ENABLE		(1 << 6)
+#define TIMEREG_CR_3_CLOCK		(1 << 7)
+#define TIMEREG_CR_3_INT		(1 << 8)
+#define TIMEREG_CR_COUNT_UP		(1 << 9)
+#define TIMEREG_CR_COUNT_DOWN	(0 << 9)
+
+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)
+{
+	u32 u = readl(base + TIMER_CR);
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_RESUME:
+	case CLOCK_EVT_MODE_ONESHOT:
+		u &= ~TIMEREG_CR_1_ENABLE;
+		writel(u, 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);
+		u |= TIMEREG_CR_1_ENABLE;
+		writel(u, base + TIMER_CR);
+		break;
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	default:
+		u &= ~TIMEREG_CR_1_ENABLE;
+		writel(u, base + TIMER_CR);
+		break;
+	}
+}
+
+static int moxart_clkevt_next_event(unsigned long cycles,
+	struct clock_event_device *unused)
+{
+	u32 u;
+	u = readl(base + TIMER1_BASE + REG_COUNT) - cycles;
+	writel(u, base + TIMER1_BASE + REG_MATCH1);
+	u = readl(base + TIMER_CR) | TIMEREG_CR_1_ENABLE;
+	writel(u, 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: failed to map base\n", node->full_name);
+
+	irq = irq_of_parse_and_map(node, 0);
+	if (irq <= 0)
+		panic("%s: can't parse IRQ\n", node->full_name);
+
+	ret = setup_irq(irq, &moxart_timer_irq);
+	if (ret) {
+		pr_err("%s: failed to setup IRQ %d\n", node->full_name, irq);
+		return;
+	}
+
+	clk = of_clk_get(node, 0);
+	if (IS_ERR(clk)) {
+		pr_err("%s: of_clk_get failed\n", __func__);
+		return;
+	}
+
+	pclk = clk_get_rate(clk);
+	clock_count_per_tick = DIV_ROUND_CLOSEST(pclk, HZ);
+
+	writel(~0, base + TIMER2_BASE + REG_LOAD);
+
+	writel(TIMEREG_CR_2_ENABLE, base + TIMER_CR);
+
+	if (clocksource_mmio_init(base + TIMER2_BASE + REG_COUNT,
+					"moxart_timer", pclk, 200, 32,
+					clocksource_mmio_readl_down)) {
+		pr_err("%s: clocksource_mmio_init failed\n", __func__);
+		return;
+	}
+
+	moxart_clockevent.cpumask = cpumask_of(0);
+
+	clockevents_config_and_register(&moxart_clockevent, pclk,
+					0x4, 0xf0000000);
+
+	pr_info("%s: %s finished pclk=%lu HZ=%d IRQ=%d\n",
+			node->full_name, __func__, pclk, HZ, irq);
+}
+CLOCKSOURCE_OF_DECLARE(moxart, "moxa,moxart-timer", moxart_timer_init);
+
-- 
1.8.2.1