ARM: at91: time: move the system timer driver to drivers/clocksource

Import at91rm9200_time.c from mach-at91 as timer-atmel-st.c. Further cleanup is
required to get rid of the mach-at91 headers.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

drivers/clocksource/Kconfig

@@ -143,6 +143,10 @@ config ATMEL_PIT
 	select CLKSRC_OF if OF
 	def_bool SOC_AT91SAM9 || SOC_SAMA5
 
+config ATMEL_ST
+	bool
+	select CLKSRC_OF
+
 config CLKSRC_METAG_GENERIC
 	def_bool y if METAG
 	help

drivers/clocksource/Makefile

@@ -1,5 +1,6 @@
 obj-$(CONFIG_CLKSRC_OF)	+= clksrc-of.o
 obj-$(CONFIG_ATMEL_PIT)		+= timer-atmel-pit.o
+obj-$(CONFIG_ATMEL_ST)		+= timer-atmel-st.o
 obj-$(CONFIG_ATMEL_TCB_CLKSRC)	+= tcb_clksrc.o
 obj-$(CONFIG_X86_PM_TIMER)	+= acpi_pm.o
 obj-$(CONFIG_SCx200HR_TIMER)	+= scx200_hrt.o

drivers/clocksource/timer-atmel-st.c

@@ -0,0 +1,253 @@
+/*
+ * linux/arch/arm/mach-at91/at91rm9200_time.c
+ *
+ *  Copyright (C) 2003 SAN People
+ *  Copyright (C) 2003 ATMEL
+ *
+ * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/clockchips.h>
+#include <linux/export.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+#include <asm/mach/time.h>
+
+#include <mach/at91_st.h>
+#include <mach/hardware.h>
+
+static unsigned long last_crtr;
+static u32 irqmask;
+static struct clock_event_device clkevt;
+
+#define RM9200_TIMER_LATCH	((AT91_SLOW_CLOCK + HZ/2) / HZ)
+
+/*
+ * The ST_CRTR is updated asynchronously to the master clock ... but
+ * the updates as seen by the CPU don't seem to be strictly monotonic.
+ * Waiting until we read the same value twice avoids glitching.
+ */
+static inline unsigned long read_CRTR(void)
+{
+	unsigned long x1, x2;
+
+	x1 = at91_st_read(AT91_ST_CRTR);
+	do {
+		x2 = at91_st_read(AT91_ST_CRTR);
+		if (x1 == x2)
+			break;
+		x1 = x2;
+	} while (1);
+	return x1;
+}
+
+/*
+ * IRQ handler for the timer.
+ */
+static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
+{
+	u32	sr = at91_st_read(AT91_ST_SR) & irqmask;
+
+	/*
+	 * irqs should be disabled here, but as the irq is shared they are only
+	 * guaranteed to be off if the timer irq is registered first.
+	 */
+	WARN_ON_ONCE(!irqs_disabled());
+
+	/* simulate "oneshot" timer with alarm */
+	if (sr & AT91_ST_ALMS) {
+		clkevt.event_handler(&clkevt);
+		return IRQ_HANDLED;
+	}
+
+	/* periodic mode should handle delayed ticks */
+	if (sr & AT91_ST_PITS) {
+		u32	crtr = read_CRTR();
+
+		while (((crtr - last_crtr) & AT91_ST_CRTV) >= RM9200_TIMER_LATCH) {
+			last_crtr += RM9200_TIMER_LATCH;
+			clkevt.event_handler(&clkevt);
+		}
+		return IRQ_HANDLED;
+	}
+
+	/* this irq is shared ... */
+	return IRQ_NONE;
+}
+
+static struct irqaction at91rm9200_timer_irq = {
+	.name		= "at91_tick",
+	.flags		= IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
+	.handler	= at91rm9200_timer_interrupt,
+	.irq		= NR_IRQS_LEGACY + AT91_ID_SYS,
+};
+
+static cycle_t read_clk32k(struct clocksource *cs)
+{
+	return read_CRTR();
+}
+
+static struct clocksource clk32k = {
+	.name		= "32k_counter",
+	.rating		= 150,
+	.read		= read_clk32k,
+	.mask		= CLOCKSOURCE_MASK(20),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static void
+clkevt32k_mode(enum clock_event_mode mode, struct clock_event_device *dev)
+{
+	/* Disable and flush pending timer interrupts */
+	at91_st_write(AT91_ST_IDR, AT91_ST_PITS | AT91_ST_ALMS);
+	at91_st_read(AT91_ST_SR);
+
+	last_crtr = read_CRTR();
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		/* PIT for periodic irqs; fixed rate of 1/HZ */
+		irqmask = AT91_ST_PITS;
+		at91_st_write(AT91_ST_PIMR, RM9200_TIMER_LATCH);
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+		/* ALM for oneshot irqs, set by next_event()
+		 * before 32 seconds have passed
+		 */
+		irqmask = AT91_ST_ALMS;
+		at91_st_write(AT91_ST_RTAR, last_crtr);
+		break;
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_RESUME:
+		irqmask = 0;
+		break;
+	}
+	at91_st_write(AT91_ST_IER, irqmask);
+}
+
+static int
+clkevt32k_next_event(unsigned long delta, struct clock_event_device *dev)
+{
+	u32		alm;
+	int		status = 0;
+
+	BUG_ON(delta < 2);
+
+	/* The alarm IRQ uses absolute time (now+delta), not the relative
+	 * time (delta) in our calling convention.  Like all clockevents
+	 * using such "match" hardware, we have a race to defend against.
+	 *
+	 * Our defense here is to have set up the clockevent device so the
+	 * delta is at least two.  That way we never end up writing RTAR
+	 * with the value then held in CRTR ... which would mean the match
+	 * wouldn't trigger until 32 seconds later, after CRTR wraps.
+	 */
+	alm = read_CRTR();
+
+	/* Cancel any pending alarm; flush any pending IRQ */
+	at91_st_write(AT91_ST_RTAR, alm);
+	at91_st_read(AT91_ST_SR);
+
+	/* Schedule alarm by writing RTAR. */
+	alm += delta;
+	at91_st_write(AT91_ST_RTAR, alm);
+
+	return status;
+}
+
+static struct clock_event_device clkevt = {
+	.name		= "at91_tick",
+	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+	.rating		= 150,
+	.set_next_event	= clkevt32k_next_event,
+	.set_mode	= clkevt32k_mode,
+};
+
+void __iomem *at91_st_base;
+EXPORT_SYMBOL_GPL(at91_st_base);
+
+static const struct of_device_id at91rm9200_st_timer_ids[] = {
+	{ .compatible = "atmel,at91rm9200-st" },
+	{ /* sentinel */ }
+};
+
+static int __init of_at91rm9200_st_init(void)
+{
+	struct device_node *np;
+	int ret;
+
+	np = of_find_matching_node(NULL, at91rm9200_st_timer_ids);
+	if (!np)
+		goto err;
+
+	at91_st_base = of_iomap(np, 0);
+	if (!at91_st_base)
+		goto node_err;
+
+	/* Get the interrupts property */
+	ret = irq_of_parse_and_map(np, 0);
+	if (!ret)
+		goto ioremap_err;
+	at91rm9200_timer_irq.irq = ret;
+
+	of_node_put(np);
+
+	return 0;
+
+ioremap_err:
+	iounmap(at91_st_base);
+node_err:
+	of_node_put(np);
+err:
+	return -EINVAL;
+}
+
+/*
+ * ST (system timer) module supports both clockevents and clocksource.
+ */
+static void __init atmel_st_timer_init(struct device_node *node)
+{
+	/* For device tree enabled device: initialize here */
+	of_at91rm9200_st_init();
+
+	/* Disable all timer interrupts, and clear any pending ones */
+	at91_st_write(AT91_ST_IDR,
+		AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS);
+	at91_st_read(AT91_ST_SR);
+
+	/* Make IRQs happen for the system timer */
+	setup_irq(at91rm9200_timer_irq.irq, &at91rm9200_timer_irq);
+
+	/* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
+	 * directly for the clocksource and all clockevents, after adjusting
+	 * its prescaler from the 1 Hz default.
+	 */
+	at91_st_write(AT91_ST_RTMR, 1);
+
+	/* Setup timer clockevent, with minimum of two ticks (important!!) */
+	clkevt.cpumask = cpumask_of(0);
+	clockevents_config_and_register(&clkevt, AT91_SLOW_CLOCK,
+					2, AT91_ST_ALMV);
+
+	/* register clocksource */
+	clocksource_register_hz(&clk32k, AT91_SLOW_CLOCK);
+}
+CLOCKSOURCE_OF_DECLARE(atmel_st_timer, "atmel,at91rm9200-st",
+		       atmel_st_timer_init);