ARM: imx: Add EPIT support

The Enhanced Periodic Interrupt Timer (EPIT) is found on newer
i.MX SoCs and can be used as an alternative system timer.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

1 files changed, 242 insertions, 0 deletions

diff --git a/arch/arm/plat-mxc/epit.c b/arch/arm/plat-mxc/epit.c
new file mode 100644
index 000000000000..ee9582f4972e
--- /dev/null
+++ b/arch/arm/plat-mxc/epit.c
@@ -0,0 +1,242 @@
+/*
+ *  linux/arch/arm/plat-mxc/epit.c
+ *
+ *  Copyright (C) 2010 Sascha Hauer <s.hauer@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.
+ */
+
+#define EPITCR          0x00
+#define EPITSR          0x04
+#define EPITLR          0x08
+#define EPITCMPR        0x0c
+#define EPITCNR         0x10
+
+#define EPITCR_EN                       (1 << 0)
+#define EPITCR_ENMOD                    (1 << 1)
+#define EPITCR_OCIEN                    (1 << 2)
+#define EPITCR_RLD                      (1 << 3)
+#define EPITCR_PRESC(x)                 (((x) & 0xfff) << 4)
+#define EPITCR_SWR                      (1 << 16)
+#define EPITCR_IOVW                     (1 << 17)
+#define EPITCR_DBGEN                    (1 << 18)
+#define EPITCR_WAITEN                   (1 << 19)
+#define EPITCR_RES                      (1 << 20)
+#define EPITCR_STOPEN                   (1 << 21)
+#define EPITCR_OM_DISCON                (0 << 22)
+#define EPITCR_OM_TOGGLE                (1 << 22)
+#define EPITCR_OM_CLEAR                 (2 << 22)
+#define EPITCR_OM_SET                   (3 << 22)
+#define EPITCR_CLKSRC_OFF               (0 << 24)
+#define EPITCR_CLKSRC_PERIPHERAL        (1 << 24)
+#define EPITCR_CLKSRC_REF_HIGH          (1 << 24)
+#define EPITCR_CLKSRC_REF_LOW           (3 << 24)
+
+#define EPITSR_OCIF                     (1 << 0)
+
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/clockchips.h>
+#include <linux/clk.h>
+
+#include <mach/hardware.h>
+#include <asm/mach/time.h>
+#include <mach/common.h>
+
+static struct clock_event_device clockevent_epit;
+static enum clock_event_mode clockevent_mode = CLOCK_EVT_MODE_UNUSED;
+
+static void __iomem *timer_base;
+
+static inline void epit_irq_disable(void)
+{
+        u32 val;
+
+        val = __raw_readl(timer_base + EPITCR);
+        val &= ~EPITCR_OCIEN;
+        __raw_writel(val, timer_base + EPITCR);
+}
+
+static inline void epit_irq_enable(void)
+{
+        u32 val;
+
+        val = __raw_readl(timer_base + EPITCR);
+        val |= EPITCR_OCIEN;
+        __raw_writel(val, timer_base + EPITCR);
+}
+
+static void epit_irq_acknowledge(void)
+{
+        __raw_writel(EPITSR_OCIF, timer_base + EPITSR);
+}
+
+static cycle_t epit_read(struct clocksource *cs)
+{
+        return 0 - __raw_readl(timer_base + EPITCNR);
+}
+
+static struct clocksource clocksource_epit = {
+        .name           = "epit",
+        .rating         = 200,
+        .read           = epit_read,
+        .mask           = CLOCKSOURCE_MASK(32),
+        .shift          = 20,
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init epit_clocksource_init(struct clk *timer_clk)
+{
+        unsigned int c = clk_get_rate(timer_clk);
+
+        clocksource_epit.mult = clocksource_hz2mult(c,
+                                        clocksource_epit.shift);
+        clocksource_register(&clocksource_epit);
+
+        return 0;
+}
+
+/* clock event */
+
+static int epit_set_next_event(unsigned long evt,
+                              struct clock_event_device *unused)
+{
+        unsigned long tcmp;
+
+        tcmp = __raw_readl(timer_base + EPITCNR);
+
+        __raw_writel(tcmp - evt, timer_base + EPITCMPR);
+
+        return 0;
+}
+
+static void epit_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 epit_set_next_event()
+         */
+        local_irq_save(flags);
+
+        /* Disable interrupt in GPT module */
+        epit_irq_disable();
+
+        if (mode != clockevent_mode) {
+                /* Set event time into far-far future */
+
+                /* Clear pending interrupt */
+                epit_irq_acknowledge();
+        }
+
+        /* Remember timer mode */
+        clockevent_mode = mode;
+        local_irq_restore(flags);
+
+        switch (mode) {
+        case CLOCK_EVT_MODE_PERIODIC:
+                printk(KERN_ERR "epit_set_mode: Periodic mode is not "
+                                "supported for i.MX EPIT\n");
+                break;
+        case CLOCK_EVT_MODE_ONESHOT:
+        /*
+         * Do not put overhead of interrupt enable/disable into
+         * epit_set_next_event(), the core has about 4 minutes
+         * to call epit_set_next_event() or shutdown clock after
+         * mode switching
+         */
+                local_irq_save(flags);
+                epit_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 epit_timer_interrupt(int irq, void *dev_id)
+{
+        struct clock_event_device *evt = &clockevent_epit;
+
+        epit_irq_acknowledge();
+
+        evt->event_handler(evt);
+
+        return IRQ_HANDLED;
+}
+
+static struct irqaction epit_timer_irq = {
+        .name           = "i.MX EPIT Timer Tick",
+        .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
+        .handler        = epit_timer_interrupt,
+};
+
+static struct clock_event_device clockevent_epit = {
+        .name           = "epit",
+        .features       = CLOCK_EVT_FEAT_ONESHOT,
+        .shift          = 32,
+        .set_mode       = epit_set_mode,
+        .set_next_event = epit_set_next_event,
+        .rating         = 200,
+};
+
+static int __init epit_clockevent_init(struct clk *timer_clk)
+{
+        unsigned int c = clk_get_rate(timer_clk);
+
+        clockevent_epit.mult = div_sc(c, NSEC_PER_SEC,
+                                        clockevent_epit.shift);
+        clockevent_epit.max_delta_ns =
+                        clockevent_delta2ns(0xfffffffe, &clockevent_epit);
+        clockevent_epit.min_delta_ns =
+                        clockevent_delta2ns(0x800, &clockevent_epit);
+
+        clockevent_epit.cpumask = cpumask_of(0);
+
+        clockevents_register_device(&clockevent_epit);
+
+        return 0;
+}
+
+void __init epit_timer_init(struct clk *timer_clk, void __iomem *base, int irq)
+{
+        clk_enable(timer_clk);
+
+        timer_base = base;
+
+        /*
+         * Initialise to a known state (all timers off, and timing reset)
+         */
+        __raw_writel(0x0, timer_base + EPITCR);
+
+        __raw_writel(0xffffffff, timer_base + EPITLR);
+        __raw_writel(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
+                        timer_base + EPITCR);
+
+        /* init and register the timer to the framework */
+        epit_clocksource_init(timer_clk);
+        epit_clockevent_init(timer_clk);
+
+        /* Make irqs happen */
+        setup_irq(irq, &epit_timer_irq);
+}