i.MXC family: Adding timer support

This patch adds timer support for the i.MX machine family. This code can
be used on the following machs:

 - i.MX1 (tested)
 - i.MX2 (i.MX21 (to be tested), i.MX27 (tested))
 - i.MX3 (i.MX31 (tested))

TODO: It seems impossible to build a kernel for more than one CPU because the
timer do not follow the platform device rules. So it does only work if
timer 1 can be accessed on all CPUs at the same address.

Signed-off-by: Juergen Beisert <j.beisert@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 228 insertions, 0 deletions

diff --git a/arch/arm/plat-mxc/time.c b/arch/arm/plat-mxc/time.c
new file mode 100644
index 0000000..3bf8634
--- /dev/null
+++ b/arch/arm/plat-mxc/time.c
@@ -0,0 +1,228 @@
+/*
+ *  linux/arch/arm/plat-mxc/time.c
+ *
+ *  Copyright (C) 2000-2001 Deep Blue Solutions
+ *  Copyright (C) 2002 Shane Nay (shane@minirl.com)
+ *  Copyright (C) 2006-2007 Pavel Pisa (ppisa@pikron.com)
+ *  Copyright (C) 2008 Juergen Beisert (kernel@pengutronix.de)
+ *
+ * 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.
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/clockchips.h>
+#include <linux/clk.h>
+
+#include <asm/hardware.h>
+#include <asm/mach/time.h>
+#include <asm/arch/common.h>
+#include <asm/arch/mxc_timer.h>
+
+static struct clock_event_device clockevent_mxc;
+static enum clock_event_mode clockevent_mode = CLOCK_EVT_MODE_UNUSED;
+
+/* clock source for the timer */
+static struct clk *timer_clk;
+
+/* clock source */
+
+static cycle_t mxc_get_cycles(void)
+{
+	return __raw_readl(TIMER_BASE + MXC_TCN);
+}
+
+static struct clocksource clocksource_mxc = {
+	.name 		= "mxc_timer1",
+	.rating		= 200,
+	.read		= mxc_get_cycles,
+	.mask		= CLOCKSOURCE_MASK(32),
+	.shift 		= 20,
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init mxc_clocksource_init(void)
+{
+	unsigned int clock;
+
+	clock = clk_get_rate(timer_clk);
+
+	clocksource_mxc.mult = clocksource_hz2mult(clock,
+					clocksource_mxc.shift);
+	clocksource_register(&clocksource_mxc);
+
+	return 0;
+}
+
+/* clock event */
+
+static int mxc_set_next_event(unsigned long evt,
+			      struct clock_event_device *unused)
+{
+	unsigned long tcmp;
+
+	tcmp = __raw_readl(TIMER_BASE + MXC_TCN) + evt;
+	__raw_writel(tcmp, TIMER_BASE + MXC_TCMP);
+
+	return (int)(tcmp - __raw_readl(TIMER_BASE + MXC_TCN)) < 0 ?
+				-ETIME : 0;
+}
+
+#ifdef DEBUG
+static const char *clock_event_mode_label[] = {
+	[CLOCK_EVT_MODE_PERIODIC] = "CLOCK_EVT_MODE_PERIODIC",
+	[CLOCK_EVT_MODE_ONESHOT]  = "CLOCK_EVT_MODE_ONESHOT",
+	[CLOCK_EVT_MODE_SHUTDOWN] = "CLOCK_EVT_MODE_SHUTDOWN",
+	[CLOCK_EVT_MODE_UNUSED]   = "CLOCK_EVT_MODE_UNUSED"
+};
+#endif /* DEBUG */
+
+static void mxc_set_mode(enum clock_event_mode mode,
+				struct clock_event_device *evt)
+{
+	unsigned long flags;
+
+	/*
+	 * The timer interrupt generation is disabled at least
+	 * for enough time to call mxc_set_next_event()
+	 */
+	local_irq_save(flags);
+
+	/* Disable interrupt in GPT module */
+	gpt_irq_disable();
+
+	if (mode != clockevent_mode) {
+		/* Set event time into far-far future */
+		__raw_writel(__raw_readl(TIMER_BASE + MXC_TCN) - 3,
+				TIMER_BASE + MXC_TCMP);
+		/* Clear pending interrupt */
+		gpt_irq_acknowledge();
+	}
+
+#ifdef DEBUG
+	printk(KERN_INFO "mxc_set_mode: changing mode from %s to %s\n",
+		clock_event_mode_label[clockevent_mode],
+		clock_event_mode_label[mode]);
+#endif /* DEBUG */
+
+	/* Remember timer mode */
+	clockevent_mode = mode;
+	local_irq_restore(flags);
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		printk(KERN_ERR"mxc_set_mode: Periodic mode is not "
+				"supported for i.MX\n");
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+	/*
+	 * Do not put overhead of interrupt enable/disable into
+	 * mxc_set_next_event(), the core has about 4 minutes
+	 * to call mxc_set_next_event() or shutdown clock after
+	 * mode switching
+	 */
+		local_irq_save(flags);
+		gpt_irq_enable();
+		local_irq_restore(flags);
+		break;
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_RESUME:
+		/* Left event sources disabled, no more interrupts appear */
+		break;
+	}
+}
+
+/*
+ * IRQ handler for the timer
+ */
+static irqreturn_t mxc_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = &clockevent_mxc;
+	uint32_t tstat;
+
+	tstat = __raw_readl(TIMER_BASE + MXC_TSTAT);
+
+	gpt_irq_acknowledge();
+
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct irqaction mxc_timer_irq = {
+	.name		= "i.MX Timer Tick",
+	.flags		= IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
+	.handler	= mxc_timer_interrupt,
+};
+
+static struct clock_event_device clockevent_mxc = {
+	.name		= "mxc_timer1",
+	.features	= CLOCK_EVT_FEAT_ONESHOT,
+	.shift		= 32,
+	.set_mode	= mxc_set_mode,
+	.set_next_event	= mxc_set_next_event,
+	.rating		= 200,
+};
+
+static int __init mxc_clockevent_init(void)
+{
+	unsigned int clock;
+
+	clock = clk_get_rate(timer_clk);
+
+	clockevent_mxc.mult = div_sc(clock, NSEC_PER_SEC,
+					clockevent_mxc.shift);
+	clockevent_mxc.max_delta_ns =
+			clockevent_delta2ns(0xfffffffe, &clockevent_mxc);
+	clockevent_mxc.min_delta_ns =
+			clockevent_delta2ns(0xff, &clockevent_mxc);
+
+	clockevent_mxc.cpumask = cpumask_of_cpu(0);
+
+	clockevents_register_device(&clockevent_mxc);
+
+	return 0;
+}
+
+void __init mxc_timer_init(const char *clk_timer)
+{
+	timer_clk = clk_get(NULL, clk_timer);
+	if (!timer_clk) {
+		printk(KERN_ERR"Cannot determine timer clock. Giving up.\n");
+		return;
+	}
+
+	clk_enable(timer_clk);
+
+	/*
+	 * Initialise to a known state (all timers off, and timing reset)
+	 */
+	__raw_writel(0, TIMER_BASE + MXC_TCTL);
+	__raw_writel(0, TIMER_BASE + MXC_TPRER); /* see datasheet note */
+
+	__raw_writel(TCTL_FRR |	/* free running */
+		     TCTL_VAL |	/* set clocksource and arch specific bits */
+		     TCTL_TEN,	/* start the timer */
+		     TIMER_BASE + MXC_TCTL);
+
+	/* init and register the timer to the framework */
+	mxc_clocksource_init();
+	mxc_clockevent_init();
+
+	/* Make irqs happen */
+	setup_irq(TIMER_INTERRUPT, &mxc_timer_irq);
+}
+