clocksource: Add Freescale Vybrid pit timer support

Add Freescale Vybrid Family period interrupt timer support.
Signed-off-by: Jingchang Lu <b35083@freescale.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/Kconfig

@@ -85,3 +85,8 @@ config CLKSRC_SAMSUNG_PWM
 	  Samsung S3C, S5P and Exynos SoCs, replacing an earlier driver
 	  for all devicetree enabled platforms. This driver will be
 	  needed only on systems that do not have the Exynos MCT available.
+
+config VF_PIT_TIMER
+	bool
+	help
+	  Support for Period Interrupt Timer on Freescale Vybrid Family SoCs.

drivers/clocksource/Makefile

@@ -26,6 +26,7 @@ obj-$(CONFIG_ARCH_BCM)		+= bcm_kona_timer.o
 obj-$(CONFIG_CADENCE_TTC_TIMER)	+= cadence_ttc_timer.o
 obj-$(CONFIG_CLKSRC_EXYNOS_MCT)	+= exynos_mct.o
 obj-$(CONFIG_CLKSRC_SAMSUNG_PWM)	+= samsung_pwm_timer.o
+obj-$(CONFIG_VF_PIT_TIMER)	+= vf_pit_timer.o
 
 obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
 obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o

drivers/clocksource/vf_pit_timer.c

+/*
+ * Copyright 2012-2013 Freescale Semiconductor, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/clockchips.h>
+#include <linux/clk.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <asm/sched_clock.h>
+
+/*
+ * Each pit takes 0x10 Bytes register space
+ */
+#define PITMCR		0x00
+#define PIT0_OFFSET	0x100
+#define PITn_OFFSET(n)	(PIT0_OFFSET + 0x10 * (n))
+#define PITLDVAL	0x00
+#define PITCVAL		0x04
+#define PITTCTRL	0x08
+#define PITTFLG		0x0c
+
+#define PITMCR_MDIS	(0x1 << 1)
+
+#define PITTCTRL_TEN	(0x1 << 0)
+#define PITTCTRL_TIE	(0x1 << 1)
+#define PITCTRL_CHN	(0x1 << 2)
+
+#define PITTFLG_TIF	0x1
+
+static void __iomem *clksrc_base;
+static void __iomem *clkevt_base;
+static unsigned long cycle_per_jiffy;
+
+static inline void pit_timer_enable(void)
+{
+	__raw_writel(PITTCTRL_TEN | PITTCTRL_TIE, clkevt_base + PITTCTRL);
+}
+
+static inline void pit_timer_disable(void)
+{
+	__raw_writel(0, clkevt_base + PITTCTRL);
+}
+
+static inline void pit_irq_acknowledge(void)
+{
+	__raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG);
+}
+
+static unsigned int pit_read_sched_clock(void)
+{
+	return __raw_readl(clksrc_base + PITCVAL);
+}
+
+static int __init pit_clocksource_init(unsigned long rate)
+{
+	/* set the max load value and start the clock source counter */
+	__raw_writel(0, clksrc_base + PITTCTRL);
+	__raw_writel(~0UL, clksrc_base + PITLDVAL);
+	__raw_writel(PITTCTRL_TEN, clksrc_base + PITTCTRL);
+
+	setup_sched_clock(pit_read_sched_clock, 32, rate);
+	return clocksource_mmio_init(clksrc_base + PITCVAL, "vf-pit", rate,
+			300, 32, clocksource_mmio_readl_down);
+}
+
+static int pit_set_next_event(unsigned long delta,
+				struct clock_event_device *unused)
+{
+	/*
+	 * set a new value to PITLDVAL register will not restart the timer,
+	 * to abort the current cycle and start a timer period with the new
+	 * value, the timer must be disabled and enabled again.
+	 * and the PITLAVAL should be set to delta minus one according to pit
+	 * hardware requirement.
+	 */
+	pit_timer_disable();
+	__raw_writel(delta - 1, clkevt_base + PITLDVAL);
+	pit_timer_enable();
+
+	return 0;
+}
+
+static void pit_set_mode(enum clock_event_mode mode,
+				struct clock_event_device *evt)
+{
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		pit_set_next_event(cycle_per_jiffy, evt);
+		break;
+	default:
+		break;
+	}
+}
+
+static irqreturn_t pit_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	pit_irq_acknowledge();
+
+	/*
+	 * pit hardware doesn't support oneshot, it will generate an interrupt
+	 * and reload the counter value from PITLDVAL when PITCVAL reach zero,
+	 * and start the counter again. So software need to disable the timer
+	 * to stop the counter loop in ONESHOT mode.
+	 */
+	if (likely(evt->mode == CLOCK_EVT_MODE_ONESHOT))
+		pit_timer_disable();
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct clock_event_device clockevent_pit = {
+	.name		= "VF pit timer",
+	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+	.set_mode	= pit_set_mode,
+	.set_next_event	= pit_set_next_event,
+	.rating		= 300,
+};
+
+static struct irqaction pit_timer_irq = {
+	.name		= "VF pit timer",
+	.flags		= IRQF_TIMER | IRQF_IRQPOLL,
+	.handler	= pit_timer_interrupt,
+	.dev_id		= &clockevent_pit,
+};
+
+static int __init pit_clockevent_init(unsigned long rate, int irq)
+{
+	__raw_writel(0, clkevt_base + PITTCTRL);
+	__raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG);
+
+	BUG_ON(setup_irq(irq, &pit_timer_irq));
+
+	clockevent_pit.cpumask = cpumask_of(0);
+	clockevent_pit.irq = irq;
+	/*
+	 * The value for the LDVAL register trigger is calculated as:
+	 * LDVAL trigger = (period / clock period) - 1
+	 * The pit is a 32-bit down count timer, when the conter value
+	 * reaches 0, it will generate an interrupt, thus the minimal
+	 * LDVAL trigger value is 1. And then the min_delta is
+	 * minimal LDVAL trigger value + 1, and the max_delta is full 32-bit.
+	 */
+	clockevents_config_and_register(&clockevent_pit, rate, 2, 0xffffffff);
+
+	return 0;
+}
+
+static void __init pit_timer_init(struct device_node *np)
+{
+	struct clk *pit_clk;
+	void __iomem *timer_base;
+	unsigned long clk_rate;
+	int irq;
+
+	timer_base = of_iomap(np, 0);
+	BUG_ON(!timer_base);
+
+	/*
+	 * PIT0 and PIT1 can be chained to build a 64-bit timer,
+	 * so choose PIT2 as clocksource, PIT3 as clockevent device,
+	 * and leave PIT0 and PIT1 unused for anyone else who needs them.
+	 */
+	clksrc_base = timer_base + PITn_OFFSET(2);
+	clkevt_base = timer_base + PITn_OFFSET(3);
+
+	irq = irq_of_parse_and_map(np, 0);
+	BUG_ON(irq <= 0);
+
+	pit_clk = of_clk_get(np, 0);
+	BUG_ON(IS_ERR(pit_clk));
+
+	BUG_ON(clk_prepare_enable(pit_clk));
+
+	clk_rate = clk_get_rate(pit_clk);
+	cycle_per_jiffy = clk_rate / (HZ);
+
+	/* enable the pit module */
+	__raw_writel(~PITMCR_MDIS, timer_base + PITMCR);
+
+	BUG_ON(pit_clocksource_init(clk_rate));
+
+	pit_clockevent_init(clk_rate, irq);
+}
+CLOCKSOURCE_OF_DECLARE(vf610, "fsl,vf610-pit", pit_timer_init);