diff options
Diffstat (limited to 'kernel/arch/arm/mach-imx/epit.c')
| -rw-r--r-- | kernel/arch/arm/mach-imx/epit.c | 225 |
1 files changed, 225 insertions, 0 deletions
diff --git a/kernel/arch/arm/mach-imx/epit.c b/kernel/arch/arm/mach-imx/epit.c new file mode 100644 index 000000000..074b1a81b --- /dev/null +++ b/kernel/arch/arm/mach-imx/epit.c @@ -0,0 +1,225 @@ +/* + * 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 <linux/err.h> +#include <asm/mach/time.h> + +#include "common.h" +#include "hardware.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 int __init epit_clocksource_init(struct clk *timer_clk) +{ + unsigned int c = clk_get_rate(timer_clk); + + return clocksource_mmio_init(timer_base + EPITCNR, "epit", c, 200, 32, + clocksource_mmio_readl_down); +} + +/* 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_TIMER | IRQF_IRQPOLL, + .handler = epit_timer_interrupt, +}; + +static struct clock_event_device clockevent_epit = { + .name = "epit", + .features = CLOCK_EVT_FEAT_ONESHOT, + .set_mode = epit_set_mode, + .set_next_event = epit_set_next_event, + .rating = 200, +}; + +static int __init epit_clockevent_init(struct clk *timer_clk) +{ + clockevent_epit.cpumask = cpumask_of(0); + clockevents_config_and_register(&clockevent_epit, + clk_get_rate(timer_clk), + 0x800, 0xfffffffe); + + return 0; +} + +void __init epit_timer_init(void __iomem *base, int irq) +{ + struct clk *timer_clk; + + timer_clk = clk_get_sys("imx-epit.0", NULL); + if (IS_ERR(timer_clk)) { + pr_err("i.MX epit: unable to get clk\n"); + return; + } + + clk_prepare_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); +} |