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>

2 files changed, 358 insertions, 0 deletions

diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 1efb2879a94f..9785586dc8c4 100644
--- a/drivers/clocksource/Makefile
+++ b/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
diff --git a/drivers/clocksource/sh_mtu2.c b/drivers/clocksource/sh_mtu2.c
new file mode 100644
index 000000000000..420566f4c501
--- /dev/null
+++ b/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");