[PATCH v3 03/14] picoxcell: add support for the system timers
Jamie Iles
jamie at jamieiles.com
Fri Dec 10 11:28:14 EST 2010
The picoXcell devices have 4 timers capable of generating interrupts
when they reach a predefined value and restarting and a freerunning RTC.
Use one of the interrupt capable timers as the clockevent_device and the
RTC for the clocksource and sched_clock().
v2:
- use clocksource_register_hz() and
clockevents_calc_mult_shift() rather than specifying .mult and
.shift.
v3:
- Incorporate feedback from RMK.
- Don't emulate oneshot mode in the timers, let the generic
clockevents layer do it.
- Provide a better sched_clock() based on plat-nomadik's.
- Convert to __raw_ io accessors.
Signed-off-by: Jamie Iles <jamie at jamieiles.com>
---
arch/arm/mach-picoxcell/Makefile | 3 +-
arch/arm/mach-picoxcell/picoxcell_core.h | 2 +
arch/arm/mach-picoxcell/time.c | 255 ++++++++++++++++++++++++++++++
3 files changed, 259 insertions(+), 1 deletions(-)
create mode 100644 arch/arm/mach-picoxcell/time.c
diff --git a/arch/arm/mach-picoxcell/Makefile b/arch/arm/mach-picoxcell/Makefile
index 6afe388..493ec0e 100644
--- a/arch/arm/mach-picoxcell/Makefile
+++ b/arch/arm/mach-picoxcell/Makefile
@@ -1 +1,2 @@
-obj-y := picoxcell_core.o io.o axi2cfg.o
+obj-y := picoxcell_core.o io.o axi2cfg.o \
+ time.o
diff --git a/arch/arm/mach-picoxcell/picoxcell_core.h b/arch/arm/mach-picoxcell/picoxcell_core.h
index 5b27e52..941d1a6 100644
--- a/arch/arm/mach-picoxcell/picoxcell_core.h
+++ b/arch/arm/mach-picoxcell/picoxcell_core.h
@@ -13,9 +13,11 @@
#define __ASM_ARCH_PICOXCELL_CORE_H__
struct picoxcell_soc;
+struct sys_timer;
extern void __init picoxcell_core_init(void);
extern void __init picoxcell_init_irq(void);
extern void __init picoxcell_map_io(void);
+extern struct sys_timer picoxcell_sys_timer;
#endif /* __ASM_ARCH_PICOXCELL_CORE_H__ */
diff --git a/arch/arm/mach-picoxcell/time.c b/arch/arm/mach-picoxcell/time.c
new file mode 100644
index 0000000..9864200
--- /dev/null
+++ b/arch/arm/mach-picoxcell/time.c
@@ -0,0 +1,255 @@
+/*
+ * Copyright (c) 2010 Picochip Ltd., Jamie Iles
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * All enquiries to support at picochip.com
+ */
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/cnt32_to_63.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+
+#include <asm/mach/time.h>
+
+#include <mach/hardware.h>
+
+#include "picoxcell_core.h"
+#include "soc.h"
+
+enum timer_id {
+ TIMER_ID_CLOCKEVENT,
+ TIMER_ID_CLOCKSOURCE,
+ NR_TIMERS,
+};
+
+struct timer_instance {
+ void __iomem *base;
+ struct irqaction irqaction;
+};
+
+static u32 sched_mult, sched_shift;
+static struct timer_list cnt32_to_63_keepwarm_timer;
+
+/*
+ * We expect to have 2 timers - a freerunning one for the clock source and a
+ * periodic/oneshot one for the clock_event_device.
+ */
+static struct timer_instance timers[NR_TIMERS];
+
+static void timer_set_mode(enum clock_event_mode mode,
+ struct clock_event_device *clk)
+{
+ struct timer_instance *timer = &timers[TIMER_ID_CLOCKEVENT];
+ unsigned long load_count = DIV_ROUND_UP(CLOCK_TICK_RATE, HZ);
+
+ switch (mode) {
+ case CLOCK_EVT_MODE_PERIODIC:
+ /*
+ * By default, use the kernel tick rate. The reload value can
+ * be changed with the timer_set_next_event() function.
+ */
+ __raw_writel(load_count,
+ timer->base + TIMER_LOAD_COUNT_REG_OFFSET);
+ __raw_writel(TIMER_ENABLE | TIMER_MODE,
+ timer->base + TIMER_CONTROL_REG_OFFSET);
+ break;
+
+ case CLOCK_EVT_MODE_ONESHOT:
+ case CLOCK_EVT_MODE_UNUSED:
+ case CLOCK_EVT_MODE_SHUTDOWN:
+ default:
+ __raw_writel(0, timer->base + TIMER_CONTROL_REG_OFFSET);
+ break;
+ }
+}
+
+static int timer_set_next_event(unsigned long evt,
+ struct clock_event_device *clk)
+{
+ struct timer_instance *timer = &timers[TIMER_ID_CLOCKEVENT];
+
+ /* Disable the timer, write the new event then enable it. */
+ __raw_writel(0, timer->base + TIMER_CONTROL_REG_OFFSET);
+ __raw_writel(evt, timer->base + TIMER_LOAD_COUNT_REG_OFFSET);
+ __raw_writel(TIMER_ENABLE | TIMER_MODE,
+ timer->base + TIMER_CONTROL_REG_OFFSET);
+
+ return 0;
+}
+
+static struct clock_event_device clockevent_picoxcell = {
+ .features = CLOCK_EVT_FEAT_PERIODIC |
+ CLOCK_EVT_FEAT_ONESHOT,
+ .set_next_event = timer_set_next_event,
+ .set_mode = timer_set_mode,
+};
+
+static irqreturn_t timer_interrupt(int irq, void *dev_id)
+{
+ struct timer_instance *timer = &timers[TIMER_ID_CLOCKEVENT];
+
+ /* Clear the interrupt. */
+ __raw_readl(timer->base + TIMER_EOI_REG_OFFSET);
+
+ clockevent_picoxcell.event_handler(&clockevent_picoxcell);
+
+ return IRQ_HANDLED;
+}
+
+#define PICOXCELL_MIN_RANGE 4
+
+static void picoxcell_clockevent_init(struct picoxcell_soc *soc)
+{
+ struct timer_instance *inst = &timers[TIMER_ID_CLOCKEVENT];
+ const struct picoxcell_timer *timer = NULL;
+ int i;
+
+ for (i = 0; i < soc->nr_timers; ++i)
+ if (soc->timers[i].type == TIMER_TYPE_TIMER) {
+ timer = &soc->timers[i];
+ break;
+ }
+
+ BUG_ON(!timer);
+
+ /* Configure the interrupt for this timer. */
+ inst->irqaction.name = timer->name;
+ inst->irqaction.handler = timer_interrupt;
+ inst->irqaction.flags = IRQF_DISABLED | IRQF_TIMER | IRQF_PROBE;
+ inst->base = ioremap(timer->base, TIMER_SPACING);
+
+ clockevent_picoxcell.name = timer->name;
+ clockevents_calc_mult_shift(&clockevent_picoxcell, CLOCK_TICK_RATE,
+ PICOXCELL_MIN_RANGE);
+ clockevent_picoxcell.max_delta_ns =
+ clockevent_delta2ns(0xfffffffe, &clockevent_picoxcell);
+ clockevent_picoxcell.min_delta_ns = 50000;
+ clockevent_picoxcell.cpumask = cpumask_of(0);
+
+ /* Start with the timer disabled and the interrupt enabled. */
+ __raw_writel(0, inst->base + TIMER_CONTROL_REG_OFFSET);
+ setup_irq(timer->irq, &inst->irqaction);
+
+ clockevents_register_device(&clockevent_picoxcell);
+}
+
+static cycle_t picoxcell_rtc_get_cycles(struct clocksource *cs)
+{
+ struct timer_instance *inst = &timers[TIMER_ID_CLOCKSOURCE];
+
+ return __raw_readl(inst->base + RTCLK_CCV_REG_OFFSET);
+}
+
+/*
+ * Kernel assumes that sched_clock can be called early but may not have
+ * things ready yet.
+ */
+static cycle_t read_dummy(struct clocksource *cs)
+{
+ return 0;
+}
+
+static struct clocksource clocksource_picoxcell = {
+ .name = "rtc",
+ .rating = 300,
+ .read = read_dummy,
+ .mask = CLOCKSOURCE_MASK(32),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static void __init picoxcell_clocksource_init(struct picoxcell_soc *soc)
+{
+ const struct picoxcell_timer *timer = NULL;
+ int i;
+
+ for (i = 0; i < soc->nr_timers; ++i)
+ if (soc->timers[i].type == TIMER_TYPE_RTC) {
+ timer = &soc->timers[i];
+ break;
+ }
+
+ BUG_ON(!timer);
+
+ timers[TIMER_ID_CLOCKSOURCE].base = ioremap(timer->base, SZ_4K);
+
+ /* The RTC is always running. We don't need to do any initialization. */
+ clocksource_picoxcell.read = picoxcell_rtc_get_cycles;
+ clocksource_register_hz(&clocksource_picoxcell, CLOCK_TICK_RATE);
+}
+
+/*
+ * Overwrite weak default sched_clock with something more precise.
+ *
+ * We use the same idea as plat-nomadik to keep sched_clock() from wrapping
+ * too often as the RTC is clocked at 200MHz. A wrap once a year is
+ * acceptable.
+ */
+#define SCHED_CLOCK_MIN_WRAP (3600 * 24 * 365)
+unsigned long long notrace sched_clock(void)
+{
+ u64 cycles = cnt32_to_63(__raw_readl(IO_ADDRESS(PICOXCELL_RTCLK_BASE) +
+ RTCLK_CCV_REG_OFFSET));
+ return (cycles * sched_mult) >> sched_shift;
+}
+
+/* Just kick sched_clock at least once every half period. */
+static void cnt32_to_63_keepwarm(unsigned long data)
+{
+ mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data));
+ (void)sched_clock();
+}
+
+static void __init picoxcell_sched_clock_init(unsigned long rate)
+{
+ u32 v;
+ unsigned long delta;
+ u64 days;
+
+ /* Find the appropriate mult and shift factors. */
+ clocks_calc_mult_shift(&sched_mult, &sched_shift, rate,
+ NSEC_PER_SEC, SCHED_CLOCK_MIN_WRAP);
+ /*
+ * The multiply needs to be an even number to get rid of bit 63 for
+ * cnt_32_to_63().
+ */
+ if (sched_mult & 1)
+ sched_mult++;
+
+ /* Take the max counter value and scale it. */
+ days = (~0LLU * sched_mult) >> sched_shift;
+ do_div(days, NSEC_PER_SEC);
+ do_div(days, 3600 * 24);
+
+ pr_info("sched_clock: using %d bits @ %lu Hz wrap in %lu days\n",
+ (64 - sched_shift), rate, (unsigned long)days);
+
+ /*
+ * Program a timer to kick us at half 32 bit wraparound.
+ * Formula: seconds per wrap = (2^32) / f.
+ */
+ v = (0xFFFFFFFFUL / rate) / 2;
+ pr_debug("sched_clock: prescaled timer rate: %lu Hz, initialize keepwarm timer every %u seconds\n",
+ rate, v);
+
+ /* Convert seconds into jiffies. */
+ delta = msecs_to_jiffies(v * 1000);
+ setup_timer(&cnt32_to_63_keepwarm_timer, cnt32_to_63_keepwarm, delta);
+ mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + delta));
+}
+
+static void __init picoxcell_timer_init(void)
+{
+ struct picoxcell_soc *soc = picoxcell_get_soc();
+
+ picoxcell_clocksource_init(soc);
+ picoxcell_clockevent_init(soc);
+ picoxcell_sched_clock_init(CLOCK_TICK_RATE);
+}
+
+struct sys_timer picoxcell_sys_timer = {
+ .init = picoxcell_timer_init,
+};
--
1.7.2.3
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