[PATCH v2 1/2] i.MX: Add EPIT support
Michael Grzeschik
m.grzeschik at pengutronix.de
Thu Aug 19 08:08:04 EDT 2010
From: Sascha Hauer <s.hauer at pengutronix.de>
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 at pengutronix.de>
Signed-off-by: Michael Grzeschik <m.grzeschik at pengutronix.de>
---
v1 -> v2:
added prototype in plat-mxc/include/mach/common.h
arch/arm/plat-mxc/Kconfig | 12 ++
arch/arm/plat-mxc/Makefile | 1 +
arch/arm/plat-mxc/epit.c | 243 +++++++++++++++++++++++++++++++
arch/arm/plat-mxc/include/mach/common.h | 1 +
4 files changed, 257 insertions(+), 0 deletions(-)
create mode 100644 arch/arm/plat-mxc/epit.c
diff --git a/arch/arm/plat-mxc/Kconfig b/arch/arm/plat-mxc/Kconfig
index 0527e65..448098b 100644
--- a/arch/arm/plat-mxc/Kconfig
+++ b/arch/arm/plat-mxc/Kconfig
@@ -91,6 +91,18 @@ config MXC_DEBUG_BOARD
data/address de-multiplexing and decode, signal level shift,
interrupt control and various board functions.
+config HAVE_EPIT
+ bool
+
+config MXC_USE_EPIT
+ bool "Use EPIT instead of GPT"
+ depends on HAVE_EPIT
+ help
+ Use EPIT as the system timer on systems that have it. Normally you
+ don't have a reason to do so as the EPIT has the same features and
+ uses the same clocks as the GPT. Anyway, on some systems the GPT
+ may be in use for other purposes.
+
config MXC_ULPI
bool
diff --git a/arch/arm/plat-mxc/Makefile b/arch/arm/plat-mxc/Makefile
index 78d405e..bb3443f 100644
--- a/arch/arm/plat-mxc/Makefile
+++ b/arch/arm/plat-mxc/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_ARCH_MXC_IOMUX_V3) += iomux-v3.o
obj-$(CONFIG_MXC_PWM) += pwm.o
obj-$(CONFIG_USB_EHCI_MXC) += ehci.o
obj-$(CONFIG_MXC_ULPI) += ulpi.o
+obj-$(CONFIG_MXC_USE_EPIT) += epit.o
obj-$(CONFIG_ARCH_MXC_AUDMUX_V1) += audmux-v1.o
obj-$(CONFIG_ARCH_MXC_AUDMUX_V2) += audmux-v2.o
obj-$(CONFIG_MXC_DEBUG_BOARD) += 3ds_debugboard.o
diff --git a/arch/arm/plat-mxc/epit.c b/arch/arm/plat-mxc/epit.c
new file mode 100644
index 0000000..4e44e8f
--- /dev/null
+++ b/arch/arm/plat-mxc/epit.c
@@ -0,0 +1,243 @@
+/*
+ * linux/arch/arm/plat-mxc/epit.c
+ *
+ * Copyright (C) 2010 Sascha Hauer <s.hauer at 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);
+}
+
diff --git a/arch/arm/plat-mxc/include/mach/common.h b/arch/arm/plat-mxc/include/mach/common.h
index 2941472..7a1e1f8 100644
--- a/arch/arm/plat-mxc/include/mach/common.h
+++ b/arch/arm/plat-mxc/include/mach/common.h
@@ -32,6 +32,7 @@ extern void mx31_init_irq(void);
extern void mx35_init_irq(void);
extern void mx51_init_irq(void);
extern void mxc91231_init_irq(void);
+extern void epit_timer_init(struct clk *timer_clk, void __iomem *base, int irq);
extern void mxc_timer_init(struct clk *timer_clk, void __iomem *, int);
extern int mx1_clocks_init(unsigned long fref);
extern int mx21_clocks_init(unsigned long lref, unsigned long fref);
--
1.7.1
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