diff options
Diffstat (limited to 'drivers/clocksource/vf_pit_timer.c')
| -rw-r--r-- | drivers/clocksource/vf_pit_timer.c | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/drivers/clocksource/vf_pit_timer.c b/drivers/clocksource/vf_pit_timer.c new file mode 100644 index 000000000..0f92089ec --- /dev/null +++ b/drivers/clocksource/vf_pit_timer.c @@ -0,0 +1,204 @@ +/* + * Copyright 2012-2013 Freescale Semiconductor, Inc. + * + * 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. + */ + +#include <linux/interrupt.h> +#include <linux/clockchips.h> +#include <linux/clk.h> +#include <linux/of_address.h> +#include <linux/of_irq.h> +#include <linux/sched_clock.h> + +/* + * Each pit takes 0x10 Bytes register space + */ +#define PITMCR 0x00 +#define PIT0_OFFSET 0x100 +#define PITn_OFFSET(n) (PIT0_OFFSET + 0x10 * (n)) +#define PITLDVAL 0x00 +#define PITCVAL 0x04 +#define PITTCTRL 0x08 +#define PITTFLG 0x0c + +#define PITMCR_MDIS (0x1 << 1) + +#define PITTCTRL_TEN (0x1 << 0) +#define PITTCTRL_TIE (0x1 << 1) +#define PITCTRL_CHN (0x1 << 2) + +#define PITTFLG_TIF 0x1 + +static void __iomem *clksrc_base; +static void __iomem *clkevt_base; +static unsigned long cycle_per_jiffy; + +static inline void pit_timer_enable(void) +{ + __raw_writel(PITTCTRL_TEN | PITTCTRL_TIE, clkevt_base + PITTCTRL); +} + +static inline void pit_timer_disable(void) +{ + __raw_writel(0, clkevt_base + PITTCTRL); +} + +static inline void pit_irq_acknowledge(void) +{ + __raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG); +} + +static u64 notrace pit_read_sched_clock(void) +{ + return ~__raw_readl(clksrc_base + PITCVAL); +} + +static int __init pit_clocksource_init(unsigned long rate) +{ + /* set the max load value and start the clock source counter */ + __raw_writel(0, clksrc_base + PITTCTRL); + __raw_writel(~0UL, clksrc_base + PITLDVAL); + __raw_writel(PITTCTRL_TEN, clksrc_base + PITTCTRL); + + sched_clock_register(pit_read_sched_clock, 32, rate); + return clocksource_mmio_init(clksrc_base + PITCVAL, "vf-pit", rate, + 300, 32, clocksource_mmio_readl_down); +} + +static int pit_set_next_event(unsigned long delta, + struct clock_event_device *unused) +{ + /* + * set a new value to PITLDVAL register will not restart the timer, + * to abort the current cycle and start a timer period with the new + * value, the timer must be disabled and enabled again. + * and the PITLAVAL should be set to delta minus one according to pit + * hardware requirement. + */ + pit_timer_disable(); + __raw_writel(delta - 1, clkevt_base + PITLDVAL); + pit_timer_enable(); + + return 0; +} + +static int pit_shutdown(struct clock_event_device *evt) +{ + pit_timer_disable(); + return 0; +} + +static int pit_set_periodic(struct clock_event_device *evt) +{ + pit_set_next_event(cycle_per_jiffy, evt); + return 0; +} + +static irqreturn_t pit_timer_interrupt(int irq, void *dev_id) +{ + struct clock_event_device *evt = dev_id; + + pit_irq_acknowledge(); + + /* + * pit hardware doesn't support oneshot, it will generate an interrupt + * and reload the counter value from PITLDVAL when PITCVAL reach zero, + * and start the counter again. So software need to disable the timer + * to stop the counter loop in ONESHOT mode. + */ + if (likely(clockevent_state_oneshot(evt))) + pit_timer_disable(); + + evt->event_handler(evt); + + return IRQ_HANDLED; +} + +static struct clock_event_device clockevent_pit = { + .name = "VF pit timer", + .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT, + .set_state_shutdown = pit_shutdown, + .set_state_periodic = pit_set_periodic, + .set_next_event = pit_set_next_event, + .rating = 300, +}; + +static struct irqaction pit_timer_irq = { + .name = "VF pit timer", + .flags = IRQF_TIMER | IRQF_IRQPOLL, + .handler = pit_timer_interrupt, + .dev_id = &clockevent_pit, +}; + +static int __init pit_clockevent_init(unsigned long rate, int irq) +{ + __raw_writel(0, clkevt_base + PITTCTRL); + __raw_writel(PITTFLG_TIF, clkevt_base + PITTFLG); + + BUG_ON(setup_irq(irq, &pit_timer_irq)); + + clockevent_pit.cpumask = cpumask_of(0); + clockevent_pit.irq = irq; + /* + * The value for the LDVAL register trigger is calculated as: + * LDVAL trigger = (period / clock period) - 1 + * The pit is a 32-bit down count timer, when the conter value + * reaches 0, it will generate an interrupt, thus the minimal + * LDVAL trigger value is 1. And then the min_delta is + * minimal LDVAL trigger value + 1, and the max_delta is full 32-bit. + */ + clockevents_config_and_register(&clockevent_pit, rate, 2, 0xffffffff); + + return 0; +} + +static int __init pit_timer_init(struct device_node *np) +{ + struct clk *pit_clk; + void __iomem *timer_base; + unsigned long clk_rate; + int irq, ret; + + timer_base = of_iomap(np, 0); + if (!timer_base) { + pr_err("Failed to iomap\n"); + return -ENXIO; + } + + /* + * PIT0 and PIT1 can be chained to build a 64-bit timer, + * so choose PIT2 as clocksource, PIT3 as clockevent device, + * and leave PIT0 and PIT1 unused for anyone else who needs them. + */ + clksrc_base = timer_base + PITn_OFFSET(2); + clkevt_base = timer_base + PITn_OFFSET(3); + + irq = irq_of_parse_and_map(np, 0); + if (irq <= 0) + return -EINVAL; + + pit_clk = of_clk_get(np, 0); + if (IS_ERR(pit_clk)) + return PTR_ERR(pit_clk); + + ret = clk_prepare_enable(pit_clk); + if (ret) + return ret; + + clk_rate = clk_get_rate(pit_clk); + cycle_per_jiffy = clk_rate / (HZ); + + /* enable the pit module */ + __raw_writel(~PITMCR_MDIS, timer_base + PITMCR); + + ret = pit_clocksource_init(clk_rate); + if (ret) + return ret; + + return pit_clockevent_init(clk_rate, irq); +} +TIMER_OF_DECLARE(vf610, "fsl,vf610-pit", pit_timer_init); |