sh: CMT clockevent platform driver

SuperH CMT clockevent driver.

Both 16-bit and 32-bit CMT versions are supported, but only 32-bit
is tested. This driver contains support for both clockevents and
clocksources, but no unregistration is supported at this point.

Works fine as clock source and/or event in periodic or oneshot mode.
Tested on sh7722 and sh7723, but should work with any cpu/architecture.

This version is lacking clocksource and early platform driver support
for now - this to minimize the amount of dependencies.
Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/Kconfig

@@ -397,6 +397,14 @@ source "arch/sh/boards/Kconfig"
 
 menu "Timer and clock configuration"
 
+config SH_TIMER_CMT
+	def_bool n
+	prompt "CMT support"
+	select GENERIC_TIME
+	select GENERIC_CLOCKEVENTS
+	help
+	  This enables build of the CMT system timer driver.
+
 config SH_TMU
 	def_bool y
 	prompt "TMU timer support"

drivers/clocksource/Makefile

@@ -2,3 +2,4 @@ obj-$(CONFIG_ATMEL_TCB_CLKSRC)	+= tcb_clksrc.o
 obj-$(CONFIG_X86_CYCLONE_TIMER)	+= cyclone.o
 obj-$(CONFIG_X86_PM_TIMER)	+= acpi_pm.o
 obj-$(CONFIG_SCx200HR_TIMER)	+= scx200_hrt.o
+obj-$(CONFIG_SH_TIMER_CMT)	+= sh_cmt.o

drivers/clocksource/sh_cmt.c

+/*
+ * SuperH Timer Support - CMT
+ *
+ *  Copyright (C) 2008 Magnus Damm
+ *
+ * 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
+ *
+ * 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/init.h>
+#include <linux/bootmem.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/irq.h>
+#include <linux/err.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/sh_cmt.h>
+
+struct sh_cmt_priv {
+	void __iomem *mapbase;
+	struct clk *clk;
+	unsigned long width; /* 16 or 32 bit version of hardware block */
+	unsigned long overflow_bit;
+	unsigned long clear_bits;
+	struct irqaction irqaction;
+	struct platform_device *pdev;
+
+	unsigned long flags;
+	unsigned long match_value;
+	unsigned long next_match_value;
+	unsigned long max_match_value;
+	unsigned long rate;
+	spinlock_t lock;
+	struct clock_event_device ced;
+	unsigned long total_cycles;
+};
+
+static DEFINE_SPINLOCK(sh_cmt_lock);
+
+#define CMSTR -1 /* shared register */
+#define CMCSR 0 /* channel register */
+#define CMCNT 1 /* channel register */
+#define CMCOR 2 /* channel register */
+
+static inline unsigned long sh_cmt_read(struct sh_cmt_priv *p, int reg_nr)
+{
+	struct sh_cmt_config *cfg = p->pdev->dev.platform_data;
+	void __iomem *base = p->mapbase;
+	unsigned long offs;
+
+	if (reg_nr == CMSTR) {
+		offs = 0;
+		base -= cfg->channel_offset;
+	} else
+		offs = reg_nr;
+
+	if (p->width == 16)
+		offs <<= 1;
+	else {
+		offs <<= 2;
+		if ((reg_nr == CMCNT) || (reg_nr == CMCOR))
+			return ioread32(base + offs);
+	}
+
+	return ioread16(base + offs);
+}
+
+static inline void sh_cmt_write(struct sh_cmt_priv *p, int reg_nr,
+				unsigned long value)
+{
+	struct sh_cmt_config *cfg = p->pdev->dev.platform_data;
+	void __iomem *base = p->mapbase;
+	unsigned long offs;
+
+	if (reg_nr == CMSTR) {
+		offs = 0;
+		base -= cfg->channel_offset;
+	} else
+		offs = reg_nr;
+
+	if (p->width == 16)
+		offs <<= 1;
+	else {
+		offs <<= 2;
+		if ((reg_nr == CMCNT) || (reg_nr == CMCOR)) {
+			iowrite32(value, base + offs);
+			return;
+		}
+	}
+
+	iowrite16(value, base + offs);
+}
+
+static unsigned long sh_cmt_get_counter(struct sh_cmt_priv *p,
+					int *has_wrapped)
+{
+	unsigned long v1, v2, v3;
+
+	/* Make sure the timer value is stable. Stolen from acpi_pm.c */
+	do {
+		v1 = sh_cmt_read(p, CMCNT);
+		v2 = sh_cmt_read(p, CMCNT);
+		v3 = sh_cmt_read(p, CMCNT);
+	} while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
+			  || (v3 > v1 && v3 < v2)));
+
+	*has_wrapped = sh_cmt_read(p, CMCSR) & p->overflow_bit;
+	return v2;
+}
+
+
+static void sh_cmt_start_stop_ch(struct sh_cmt_priv *p, int start)
+{
+	struct sh_cmt_config *cfg = p->pdev->dev.platform_data;
+	unsigned long flags, value;
+
+	/* start stop register shared by multiple timer channels */
+	spin_lock_irqsave(&sh_cmt_lock, flags);
+	value = sh_cmt_read(p, CMSTR);
+
+	if (start)
+		value |= 1 << cfg->timer_bit;
+	else
+		value &= ~(1 << cfg->timer_bit);
+
+	sh_cmt_write(p, CMSTR, value);
+	spin_unlock_irqrestore(&sh_cmt_lock, flags);
+}
+
+static int sh_cmt_enable(struct sh_cmt_priv *p, unsigned long *rate)
+{
+	struct sh_cmt_config *cfg = p->pdev->dev.platform_data;
+	int ret;
+
+	/* enable clock */
+	ret = clk_enable(p->clk);
+	if (ret) {
+		pr_err("sh_cmt: cannot enable clock \"%s\"\n", cfg->clk);
+		return ret;
+	}
+	*rate = clk_get_rate(p->clk) / 8;
+
+	/* make sure channel is disabled */
+	sh_cmt_start_stop_ch(p, 0);
+
+	/* configure channel, periodic mode and maximum timeout */
+	if (p->width == 16)
+		sh_cmt_write(p, CMCSR, 0);
+	else
+		sh_cmt_write(p, CMCSR, 0x01a4);
+
+	sh_cmt_write(p, CMCOR, 0xffffffff);
+	sh_cmt_write(p, CMCNT, 0);
+
+	/* enable channel */
+	sh_cmt_start_stop_ch(p, 1);
+	return 0;
+}
+
+static void sh_cmt_disable(struct sh_cmt_priv *p)
+{
+	/* disable channel */
+	sh_cmt_start_stop_ch(p, 0);
+
+	/* stop clock */
+	clk_disable(p->clk);
+}
+
+/* private flags */
+#define FLAG_CLOCKEVENT (1 << 0)
+#define FLAG_CLOCKSOURCE (1 << 1)
+#define FLAG_REPROGRAM (1 << 2)
+#define FLAG_SKIPEVENT (1 << 3)
+#define FLAG_IRQCONTEXT (1 << 4)
+
+static void sh_cmt_clock_event_program_verify(struct sh_cmt_priv *p,
+					      int absolute)
+{
+	unsigned long new_match;
+	unsigned long value = p->next_match_value;
+	unsigned long delay = 0;
+	unsigned long now = 0;
+	int has_wrapped;
+
+	now = sh_cmt_get_counter(p, &has_wrapped);
+	p->flags |= FLAG_REPROGRAM; /* force reprogram */
+
+	if (has_wrapped) {
+		/* we're competing with the interrupt handler.
+		 *  -> let the interrupt handler reprogram the timer.
+		 *  -> interrupt number two handles the event.
+		 */
+		p->flags |= FLAG_SKIPEVENT;
+		return;
+	}
+
+	if (absolute)
+		now = 0;
+
+	do {
+		/* reprogram the timer hardware,
+		 * but don't save the new match value yet.
+		 */
+		new_match = now + value + delay;
+		if (new_match > p->max_match_value)
+			new_match = p->max_match_value;
+
+		sh_cmt_write(p, CMCOR, new_match);
+
+		now = sh_cmt_get_counter(p, &has_wrapped);
+		if (has_wrapped && (new_match > p->match_value)) {
+			/* we are changing to a greater match value,
+			 * so this wrap must be caused by the counter
+			 * matching the old value.
+			 * -> first interrupt reprograms the timer.
+			 * -> interrupt number two handles the event.
+			 */
+			p->flags |= FLAG_SKIPEVENT;
+			break;
+		}
+
+		if (has_wrapped) {
+			/* we are changing to a smaller match value,
+			 * so the wrap must be caused by the counter
+			 * matching the new value.
+			 * -> save programmed match value.
+			 * -> let isr handle the event.
+			 */
+			p->match_value = new_match;
+			break;
+		}
+
+		/* be safe: verify hardware settings */
+		if (now < new_match) {
+			/* timer value is below match value, all good.
+			 * this makes sure we won't miss any match events.
+			 * -> save programmed match value.
+			 * -> let isr handle the event.
+			 */
+			p->match_value = new_match;
+			break;
+		}
+
+		/* the counter has reached a value greater
+		 * than our new match value. and since the
+		 * has_wrapped flag isn't set we must have
+		 * programmed a too close event.
+		 * -> increase delay and retry.
+		 */
+		if (delay)
+			delay <<= 1;
+		else
+			delay = 1;
+
+		if (!delay)
+			pr_warning("sh_cmt: too long delay\n");
+
+	} while (delay);
+}
+
+static void sh_cmt_set_next(struct sh_cmt_priv *p, unsigned long delta)
+{
+	unsigned long flags;
+
+	if (delta > p->max_match_value)
+		pr_warning("sh_cmt: delta out of range\n");
+
+	spin_lock_irqsave(&p->lock, flags);
+	p->next_match_value = delta;
+	sh_cmt_clock_event_program_verify(p, 0);
+	spin_unlock_irqrestore(&p->lock, flags);
+}
+
+static irqreturn_t sh_cmt_interrupt(int irq, void *dev_id)
+{
+	struct sh_cmt_priv *p = dev_id;
+
+	/* clear flags */
+	sh_cmt_write(p, CMCSR, sh_cmt_read(p, CMCSR) & p->clear_bits);
+
+	/* update clock source counter to begin with if enabled
+	 * the wrap flag should be cleared by the timer specific
+	 * isr before we end up here.
+	 */
+	if (p->flags & FLAG_CLOCKSOURCE)
+		p->total_cycles += p->match_value;
+
+	if (!(p->flags & FLAG_REPROGRAM))
+		p->next_match_value = p->max_match_value;
+
+	p->flags |= FLAG_IRQCONTEXT;
+
+	if (p->flags & FLAG_CLOCKEVENT) {
+		if (!(p->flags & FLAG_SKIPEVENT)) {
+			if (p->ced.mode == CLOCK_EVT_MODE_ONESHOT) {
+				p->next_match_value = p->max_match_value;
+				p->flags |= FLAG_REPROGRAM;
+			}
+
+			p->ced.event_handler(&p->ced);
+		}
+	}
+
+	p->flags &= ~FLAG_SKIPEVENT;
+
+	if (p->flags & FLAG_REPROGRAM) {
+		p->flags &= ~FLAG_REPROGRAM;
+		sh_cmt_clock_event_program_verify(p, 1);
+
+		if (p->flags & FLAG_CLOCKEVENT)
+			if ((p->ced.mode == CLOCK_EVT_MODE_SHUTDOWN)
+			    || (p->match_value == p->next_match_value))
+				p->flags &= ~FLAG_REPROGRAM;
+	}
+
+	p->flags &= ~FLAG_IRQCONTEXT;
+
+	return IRQ_HANDLED;
+}
+
+static int sh_cmt_start(struct sh_cmt_priv *p, unsigned long flag)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&p->lock, flags);
+
+	if (!(p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
+		ret = sh_cmt_enable(p, &p->rate);
+
+	if (ret)
+		goto out;
+	p->flags |= flag;
+
+	/* setup timeout if no clockevent */
+	if ((flag == FLAG_CLOCKSOURCE) && (!(p->flags & FLAG_CLOCKEVENT)))
+		sh_cmt_set_next(p, p->max_match_value);
+ out:
+	spin_unlock_irqrestore(&p->lock, flags);
+
+	return ret;
+}
+
+static void sh_cmt_stop(struct sh_cmt_priv *p, unsigned long flag)
+{
+	unsigned long flags;
+	unsigned long f;
+
+	spin_lock_irqsave(&p->lock, flags);
+
+	f = p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE);
+	p->flags &= ~flag;
+
+	if (f && !(p->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
+		sh_cmt_disable(p);
+
+	/* adjust the timeout to maximum if only clocksource left */
+	if ((flag == FLAG_CLOCKEVENT) && (p->flags & FLAG_CLOCKSOURCE))
+		sh_cmt_set_next(p, p->max_match_value);
+
+	spin_unlock_irqrestore(&p->lock, flags);
+}
+
+static struct sh_cmt_priv *ced_to_sh_cmt(struct clock_event_device *ced)
+{
+	return container_of(ced, struct sh_cmt_priv, ced);
+}
+
+static void sh_cmt_clock_event_start(struct sh_cmt_priv *p, int periodic)
+{
+	struct clock_event_device *ced = &p->ced;
+
+	sh_cmt_start(p, FLAG_CLOCKEVENT);
+
+	/* TODO: calculate good shift from rate and counter bit width */
+
+	ced->shift = 32;
+	ced->mult = div_sc(p->rate, NSEC_PER_SEC, ced->shift);
+	ced->max_delta_ns = clockevent_delta2ns(p->max_match_value, ced);
+	ced->min_delta_ns = clockevent_delta2ns(0x1f, ced);
+
+	if (periodic)
+		sh_cmt_set_next(p, (p->rate + HZ/2) / HZ);
+	else
+		sh_cmt_set_next(p, p->max_match_value);
+}
+
+static void sh_cmt_clock_event_mode(enum clock_event_mode mode,
+				    struct clock_event_device *ced)
+{
+	struct sh_cmt_priv *p = ced_to_sh_cmt(ced);
+
+	/* deal with old setting first */
+	switch (ced->mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+	case CLOCK_EVT_MODE_ONESHOT:
+		sh_cmt_stop(p, FLAG_CLOCKEVENT);
+		break;
+	default:
+		break;
+	}
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		pr_info("sh_cmt: %s used for periodic clock events\n",
+			ced->name);
+		sh_cmt_clock_event_start(p, 1);
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+		pr_info("sh_cmt: %s used for oneshot clock events\n",
+			ced->name);
+		sh_cmt_clock_event_start(p, 0);
+		break;
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	case CLOCK_EVT_MODE_UNUSED:
+		sh_cmt_stop(p, FLAG_CLOCKEVENT);
+		break;
+	default:
+		break;
+	}
+}
+
+static int sh_cmt_clock_event_next(unsigned long delta,
+				   struct clock_event_device *ced)
+{
+	struct sh_cmt_priv *p = ced_to_sh_cmt(ced);
+
+	BUG_ON(ced->mode != CLOCK_EVT_MODE_ONESHOT);
+	if (likely(p->flags & FLAG_IRQCONTEXT))
+		p->next_match_value = delta;
+	else
+		sh_cmt_set_next(p, delta);
+
+	return 0;
+}
+
+static void sh_cmt_register_clockevent(struct sh_cmt_priv *p,
+				       char *name, unsigned long rating)
+{
+	struct clock_event_device *ced = &p->ced;
+
+	memset(ced, 0, sizeof(*ced));
+
+	ced->name = name;
+	ced->features = CLOCK_EVT_FEAT_PERIODIC;
+	ced->features |= CLOCK_EVT_FEAT_ONESHOT;
+	ced->rating = rating;
+	ced->cpumask = cpumask_of(0);
+	ced->set_next_event = sh_cmt_clock_event_next;
+	ced->set_mode = sh_cmt_clock_event_mode;
+
+	pr_info("sh_cmt: %s used for clock events\n", ced->name);
+	ced->mult = 1; /* work around misplaced WARN_ON() in clockevents.c */
+	clockevents_register_device(ced);
+}
+
+int sh_cmt_register(struct sh_cmt_priv *p, char *name,
+		    unsigned long clockevent_rating,
+		    unsigned long clocksource_rating)
+{
+	if (p->width == (sizeof(p->max_match_value) * 8))
+		p->max_match_value = ~0;
+	else
+		p->max_match_value = (1 << p->width) - 1;
+
+	p->match_value = p->max_match_value;
+	spin_lock_init(&p->lock);
+
+	if (clockevent_rating)
+		sh_cmt_register_clockevent(p, name, clockevent_rating);
+
+	return 0;
+}
+
+static int sh_cmt_setup(struct sh_cmt_priv *p, struct platform_device *pdev)
+{
+	struct sh_cmt_config *cfg = pdev->dev.platform_data;
+	struct resource *res;
+	int irq, ret;
+	ret = -ENXIO;
+
+	memset(p, 0, sizeof(*p));
+	p->pdev = pdev;
+
+	if (!cfg) {
+		dev_err(&p->pdev->dev, "missing platform data\n");
+		goto err0;
+	}
+
+	platform_set_drvdata(pdev, p);
+
+	res = platform_get_resource(p->pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&p->pdev->dev, "failed to get I/O memory\n");
+		goto err0;
+	}
+
+	irq = platform_get_irq(p->pdev, 0);
+	if (irq < 0) {
+		dev_err(&p->pdev->dev, "failed to get irq\n");
+		goto err0;
+	}
+
+	/* map memory, let mapbase point to our channel */
+	p->mapbase = ioremap_nocache(res->start, resource_size(res));
+	if (p->mapbase == NULL) {
+		pr_err("sh_cmt: failed to remap I/O memory\n");
+		goto err0;
+	}
+
+	/* request irq using setup_irq() (too early for request_irq()) */
+	p->irqaction.name = cfg->name;
+	p->irqaction.handler = sh_cmt_interrupt;
+	p->irqaction.dev_id = p;
+	p->irqaction.flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL;
+	p->irqaction.mask = CPU_MASK_NONE;
+	ret = setup_irq(irq, &p->irqaction);
+	if (ret) {
+		pr_err("sh_cmt: failed to request irq %d\n", irq);
+		goto err1;
+	}
+
+	/* get hold of clock */
+	p->clk = clk_get(&p->pdev->dev, cfg->clk);
+	if (IS_ERR(p->clk)) {
+		pr_err("sh_cmt: cannot get clock \"%s\"\n", cfg->clk);
+		ret = PTR_ERR(p->clk);
+		goto err2;
+	}
+
+	if (resource_size(res) == 6) {
+		p->width = 16;
+		p->overflow_bit = 0x80;
+		p->clear_bits = ~0xc0;
+	} else {
+		p->width = 32;
+		p->overflow_bit = 0x8000;
+		p->clear_bits = ~0xc000;
+	}
+
+	return sh_cmt_register(p, cfg->name,
+			       cfg->clockevent_rating,
+			       cfg->clocksource_rating);
+ err2:
+	free_irq(irq, p);
+ err1:
+	iounmap(p->mapbase);
+ err0:
+	return ret;
+}
+
+static int __devinit sh_cmt_probe(struct platform_device *pdev)
+{
+	struct sh_cmt_priv *p = platform_get_drvdata(pdev);
+	int ret;
+
+	p = kmalloc(sizeof(*p), GFP_KERNEL);
+	if (p == NULL) {
+		dev_err(&pdev->dev, "failed to allocate driver data\n");
+		return -ENOMEM;
+	}
+
+	ret = sh_cmt_setup(p, pdev);
+	if (ret) {
+		kfree(p);
+
+		platform_set_drvdata(pdev, NULL);
+	}
+	return ret;
+}
+
+static int __devexit sh_cmt_remove(struct platform_device *pdev)
+{
+	return -EBUSY; /* cannot unregister clockevent and clocksource */
+}
+
+static struct platform_driver sh_cmt_device_driver = {
+	.probe		= sh_cmt_probe,
+	.remove		= __devexit_p(sh_cmt_remove),
+	.driver		= {
+		.name	= "sh_cmt",
+	}
+};
+
+static int __init sh_cmt_init(void)
+{
+	return platform_driver_register(&sh_cmt_device_driver);
+}
+
+static void __exit sh_cmt_exit(void)
+{
+	platform_driver_unregister(&sh_cmt_device_driver);
+}
+
+module_init(sh_cmt_init);
+module_exit(sh_cmt_exit);
+
+MODULE_AUTHOR("Magnus Damm");
+MODULE_DESCRIPTION("SuperH CMT Timer Driver");
+MODULE_LICENSE("GPL v2");

include/linux/sh_cmt.h

+#ifndef __SH_CMT_H__
+#define __SH_CMT_H__
+
+struct sh_cmt_config {
+	char *name;
+	unsigned long channel_offset;
+	int timer_bit;
+	char *clk;
+	unsigned long clockevent_rating;
+	unsigned long clocksource_rating;
+};
+
+#endif /* __SH_CMT_H__ */