clocksource: SuperH MTU2 Timer driver

This patch adds a MTU2 driver for the SuperH architecture.

The MTU2 driver is a platform driver with early platform
support to allow using a MTU2 channel as only clockevent
during system bootup.

Clocksource on sh2a is currently unsupported due to code
generation issues with 64-bit math, so at this point only
periodic clockevent support is in place.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/Kconfig

@@ -113,6 +113,9 @@ config SYS_SUPPORTS_PCI
 config SYS_SUPPORTS_CMT
 	bool
 
+config SYS_SUPPORTS_MTU2
+	bool
+
 config STACKTRACE_SUPPORT
 	def_bool y
 
@@ -478,6 +481,14 @@ config SH_MTU2
 	help
 	  This enables the use of the MTU2 as the system timer.
 
+config SH_TIMER_MTU2
+	bool "MTU2 timer driver"
+	depends on SYS_SUPPORTS_MTU2 && !SH_MTU2
+	default y
+	select GENERIC_CLOCKEVENTS
+	help
+	  This enables build of the MTU2 timer driver.
+
 config SH_TIMER_IRQ
 	int
 	default "28" if CPU_SUBTYPE_SH7780 || CPU_SUBTYPE_SH7785 || \

drivers/clocksource/Makefile

@@ -3,3 +3,4 @@ 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
+obj-$(CONFIG_SH_TIMER_MTU2)	+= sh_mtu2.o

drivers/clocksource/sh_mtu2.c

@@ -0,0 +1,357 @@
+/*
+ * SuperH Timer Support - MTU2
+ *
+ *  Copyright (C) 2009 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/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/irq.h>
+#include <linux/err.h>
+#include <linux/clockchips.h>
+#include <linux/sh_mtu2.h>
+
+struct sh_mtu2_priv {
+	void __iomem *mapbase;
+	struct clk *clk;
+	struct irqaction irqaction;
+	struct platform_device *pdev;
+	unsigned long rate;
+	unsigned long periodic;
+	struct clock_event_device ced;
+};
+
+static DEFINE_SPINLOCK(sh_mtu2_lock);
+
+#define TSTR -1 /* shared register */
+#define TCR  0 /* channel register */
+#define TMDR 1 /* channel register */
+#define TIOR 2 /* channel register */
+#define TIER 3 /* channel register */
+#define TSR  4 /* channel register */
+#define TCNT 5 /* channel register */
+#define TGR  6 /* channel register */
+
+static unsigned long mtu2_reg_offs[] = {
+	[TCR] = 0,
+	[TMDR] = 1,
+	[TIOR] = 2,
+	[TIER] = 4,
+	[TSR] = 5,
+	[TCNT] = 6,
+	[TGR] = 8,
+};
+
+static inline unsigned long sh_mtu2_read(struct sh_mtu2_priv *p, int reg_nr)
+{
+	struct sh_mtu2_config *cfg = p->pdev->dev.platform_data;
+	void __iomem *base = p->mapbase;
+	unsigned long offs;
+
+	if (reg_nr == TSTR)
+		return ioread8(base + cfg->channel_offset);
+
+	offs = mtu2_reg_offs[reg_nr];
+
+	if ((reg_nr == TCNT) || (reg_nr == TGR))
+		return ioread16(base + offs);
+	else
+		return ioread8(base + offs);
+}
+
+static inline void sh_mtu2_write(struct sh_mtu2_priv *p, int reg_nr,
+				unsigned long value)
+{
+	struct sh_mtu2_config *cfg = p->pdev->dev.platform_data;
+	void __iomem *base = p->mapbase;
+	unsigned long offs;
+
+	if (reg_nr == TSTR) {
+		iowrite8(value, base + cfg->channel_offset);
+		return;
+	}
+
+	offs = mtu2_reg_offs[reg_nr];
+
+	if ((reg_nr == TCNT) || (reg_nr == TGR))
+		iowrite16(value, base + offs);
+	else
+		iowrite8(value, base + offs);
+}
+
+static void sh_mtu2_start_stop_ch(struct sh_mtu2_priv *p, int start)
+{
+	struct sh_mtu2_config *cfg = p->pdev->dev.platform_data;
+	unsigned long flags, value;
+
+	/* start stop register shared by multiple timer channels */
+	spin_lock_irqsave(&sh_mtu2_lock, flags);
+	value = sh_mtu2_read(p, TSTR);
+
+	if (start)
+		value |= 1 << cfg->timer_bit;
+	else
+		value &= ~(1 << cfg->timer_bit);
+
+	sh_mtu2_write(p, TSTR, value);
+	spin_unlock_irqrestore(&sh_mtu2_lock, flags);
+}
+
+static int sh_mtu2_enable(struct sh_mtu2_priv *p)
+{
+	struct sh_mtu2_config *cfg = p->pdev->dev.platform_data;
+	int ret;
+
+	/* enable clock */
+	ret = clk_enable(p->clk);
+	if (ret) {
+		pr_err("sh_mtu2: cannot enable clock \"%s\"\n", cfg->clk);
+		return ret;
+	}
+
+	/* make sure channel is disabled */
+	sh_mtu2_start_stop_ch(p, 0);
+
+	p->rate = clk_get_rate(p->clk) / 64;
+	p->periodic = (p->rate + HZ/2) / HZ;
+
+	/* "Periodic Counter Operation" */
+	sh_mtu2_write(p, TCR, 0x23); /* TGRA clear, divide clock by 64 */
+	sh_mtu2_write(p, TIOR, 0);
+	sh_mtu2_write(p, TGR, p->periodic);
+	sh_mtu2_write(p, TCNT, 0);
+	sh_mtu2_write(p, TMDR, 0);
+	sh_mtu2_write(p, TIER, 0x01);
+
+	/* enable channel */
+	sh_mtu2_start_stop_ch(p, 1);
+
+	return 0;
+}
+
+static void sh_mtu2_disable(struct sh_mtu2_priv *p)
+{
+	/* disable channel */
+	sh_mtu2_start_stop_ch(p, 0);
+
+	/* stop clock */
+	clk_disable(p->clk);
+}
+
+static irqreturn_t sh_mtu2_interrupt(int irq, void *dev_id)
+{
+	struct sh_mtu2_priv *p = dev_id;
+
+	/* acknowledge interrupt */
+	sh_mtu2_read(p, TSR);
+	sh_mtu2_write(p, TSR, 0xfe);
+
+	/* notify clockevent layer */
+	p->ced.event_handler(&p->ced);
+	return IRQ_HANDLED;
+}
+
+static struct sh_mtu2_priv *ced_to_sh_mtu2(struct clock_event_device *ced)
+{
+	return container_of(ced, struct sh_mtu2_priv, ced);
+}
+
+static void sh_mtu2_clock_event_mode(enum clock_event_mode mode,
+				    struct clock_event_device *ced)
+{
+	struct sh_mtu2_priv *p = ced_to_sh_mtu2(ced);
+	int disabled = 0;
+
+	/* deal with old setting first */
+	switch (ced->mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		sh_mtu2_disable(p);
+		disabled = 1;
+		break;
+	default:
+		break;
+	}
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		pr_info("sh_mtu2: %s used for periodic clock events\n",
+			ced->name);
+		sh_mtu2_enable(p);
+		break;
+	case CLOCK_EVT_MODE_UNUSED:
+		if (!disabled)
+			sh_mtu2_disable(p);
+		break;
+	case CLOCK_EVT_MODE_SHUTDOWN:
+	default:
+		break;
+	}
+}
+
+static void sh_mtu2_register_clockevent(struct sh_mtu2_priv *p,
+				       char *name, unsigned long rating)
+{
+	struct clock_event_device *ced = &p->ced;
+	int ret;
+
+	memset(ced, 0, sizeof(*ced));
+
+	ced->name = name;
+	ced->features = CLOCK_EVT_FEAT_PERIODIC;
+	ced->rating = rating;
+	ced->cpumask = cpumask_of(0);
+	ced->set_mode = sh_mtu2_clock_event_mode;
+
+	ret = setup_irq(p->irqaction.irq, &p->irqaction);
+	if (ret) {
+		pr_err("sh_mtu2: failed to request irq %d\n",
+		       p->irqaction.irq);
+		return;
+	}
+
+	pr_info("sh_mtu2: %s used for clock events\n", ced->name);
+	clockevents_register_device(ced);
+}
+
+int sh_mtu2_register(struct sh_mtu2_priv *p, char *name,
+		     unsigned long clockevent_rating)
+{
+	if (clockevent_rating)
+		sh_mtu2_register_clockevent(p, name, clockevent_rating);
+
+	return 0;
+}
+
+static int sh_mtu2_setup(struct sh_mtu2_priv *p, struct platform_device *pdev)
+{
+	struct sh_mtu2_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_mtu2: failed to remap I/O memory\n");
+		goto err0;
+	}
+
+	/* setup data for setup_irq() (too early for request_irq()) */
+	p->irqaction.name = cfg->name;
+	p->irqaction.handler = sh_mtu2_interrupt;
+	p->irqaction.dev_id = p;
+	p->irqaction.irq = irq;
+	p->irqaction.flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL;
+	p->irqaction.mask = CPU_MASK_NONE;
+
+	/* get hold of clock */
+	p->clk = clk_get(&p->pdev->dev, cfg->clk);
+	if (IS_ERR(p->clk)) {
+		pr_err("sh_mtu2: cannot get clock \"%s\"\n", cfg->clk);
+		ret = PTR_ERR(p->clk);
+		goto err1;
+	}
+
+	return sh_mtu2_register(p, cfg->name, cfg->clockevent_rating);
+ err1:
+	iounmap(p->mapbase);
+ err0:
+	return ret;
+}
+
+static int __devinit sh_mtu2_probe(struct platform_device *pdev)
+{
+	struct sh_mtu2_priv *p = platform_get_drvdata(pdev);
+	struct sh_mtu2_config *cfg = pdev->dev.platform_data;
+	int ret;
+
+	if (p) {
+		pr_info("sh_mtu2: %s kept as earlytimer\n", cfg->name);
+		return 0;
+	}
+
+	p = kmalloc(sizeof(*p), GFP_KERNEL);
+	if (p == NULL) {
+		dev_err(&pdev->dev, "failed to allocate driver data\n");
+		return -ENOMEM;
+	}
+
+	ret = sh_mtu2_setup(p, pdev);
+	if (ret) {
+		kfree(p);
+		platform_set_drvdata(pdev, NULL);
+	}
+	return ret;
+}
+
+static int __devexit sh_mtu2_remove(struct platform_device *pdev)
+{
+	return -EBUSY; /* cannot unregister clockevent */
+}
+
+static struct platform_driver sh_mtu2_device_driver = {
+	.probe		= sh_mtu2_probe,
+	.remove		= __devexit_p(sh_mtu2_remove),
+	.driver		= {
+		.name	= "sh_mtu2",
+	}
+};
+
+static int __init sh_mtu2_init(void)
+{
+	return platform_driver_register(&sh_mtu2_device_driver);
+}
+
+static void __exit sh_mtu2_exit(void)
+{
+	platform_driver_unregister(&sh_mtu2_device_driver);
+}
+
+early_platform_init("earlytimer", &sh_mtu2_device_driver);
+module_init(sh_mtu2_init);
+module_exit(sh_mtu2_exit);
+
+MODULE_AUTHOR("Magnus Damm");
+MODULE_DESCRIPTION("SuperH MTU2 Timer Driver");
+MODULE_LICENSE("GPL v2");