[RFC/RFT 2/3] iop: clockevent support
Mikael Pettersson
mikpe at it.uu.se
Sat Aug 22 08:05:29 EDT 2009
This updates the IOP platform to expose the interrupting
timer 0 as a clockevent object. The timer interrupt handler
is changed to call the clockevent ->event_handler() instead
of timer_tick(), and ->set_next_event() and ->set_mode()
operations are added to allow the mode of the timer to be
updated (required for ONESHOT/NOHZ mode).
Timer 0 must now be properly initialised, which requires a
new write_tcr0() function from the mach implementation code.
Initial setup of timer 0 is also rewritten to be more robust.
On concern I have is whether the clockevent .shift
value of 20 is appropriate for timer frequencies in the
200/266/333 MHz range which seem to be typical for IOP.
Another concern I have is what the exact state changes needed
for CLK_EVT_MODE_ONESHOT and ->set_next_event are. Right now I
disable the timer both for CLK_EVT_MODE_ONESHOT and at the start
of ->set_next_event. One of these may be redundant.
Tested on n2100, compile-tested for all plat-iop machines.
Signed-off-by: Mikael Pettersson <mikpe at it.uu.se>
---
arch/arm/Kconfig | 1
arch/arm/include/asm/hardware/iop3xx.h | 5 +
arch/arm/mach-iop13xx/include/mach/time.h | 5 +
arch/arm/plat-iop/time.c | 82 ++++++++++++++++++++++++++----
4 files changed, 84 insertions(+), 9 deletions(-)
diff -rupN linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/Kconfig linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/Kconfig
--- linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/Kconfig 2009-08-22 11:13:37.000000000 +0200
+++ linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/Kconfig 2009-08-22 12:07:52.000000000 +0200
@@ -736,6 +736,7 @@ config ARCH_ACORN
config PLAT_IOP
bool
+ select GENERIC_CLOCKEVENTS
config PLAT_ORION
bool
diff -rupN linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/include/asm/hardware/iop3xx.h linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/include/asm/hardware/iop3xx.h
--- linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/include/asm/hardware/iop3xx.h 2009-08-22 12:06:28.000000000 +0200
+++ linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/include/asm/hardware/iop3xx.h 2009-08-22 12:07:52.000000000 +0200
@@ -252,6 +252,11 @@ static inline u32 read_tcr0(void)
return val;
}
+static inline void write_tcr0(u32 val)
+{
+ asm volatile("mcr p6, 0, %0, c2, c1, 0" : : "r" (val));
+}
+
static inline u32 read_tcr1(void)
{
u32 val;
diff -rupN linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/mach-iop13xx/include/mach/time.h linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/mach-iop13xx/include/mach/time.h
--- linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/mach-iop13xx/include/mach/time.h 2009-08-22 12:06:28.000000000 +0200
+++ linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/mach-iop13xx/include/mach/time.h 2009-08-22 12:07:52.000000000 +0200
@@ -83,6 +83,11 @@ static inline u32 read_tcr0(void)
return val;
}
+static inline void write_tcr0(u32 val)
+{
+ asm volatile("mcr p6, 0, %0, c2, c9, 0" : : "r" (val));
+}
+
static inline u32 read_tcr1(void)
{
u32 val;
diff -rupN linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/plat-iop/time.c linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/plat-iop/time.c
--- linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/plat-iop/time.c 2009-08-22 12:06:28.000000000 +0200
+++ linux-2.6.31-rc7.arm-iop-2-clockevents/arch/arm/plat-iop/time.c 2009-08-22 12:07:52.000000000 +0200
@@ -20,6 +20,7 @@
#include <linux/timex.h>
#include <linux/io.h>
#include <linux/clocksource.h>
+#include <linux/clockchips.h>
#include <mach/hardware.h>
#include <asm/irq.h>
#include <asm/uaccess.h>
@@ -44,7 +45,63 @@ static struct clocksource iop_clocksourc
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
+/*
+ * IOP clockevents (interrupting timer 0).
+ */
+static int iop_set_next_event(unsigned long delta,
+ struct clock_event_device *unused)
+{
+ u32 tmr = IOP_TMR_EN | IOP_TMR_PRIVILEGED
+ | IOP_TMR_RELOAD | IOP_TMR_RATIO_1_1;
+
+ BUG_ON(delta == 0);
+ write_tmr0(tmr & ~(IOP_TMR_EN | IOP_TMR_RELOAD));
+ write_tcr0(delta);
+ write_tmr0((tmr & ~IOP_TMR_RELOAD) | IOP_TMR_EN);
+
+ return 0;
+}
+
static unsigned long ticks_per_jiffy;
+
+static void iop_set_mode(enum clock_event_mode mode,
+ struct clock_event_device *unused)
+{
+ u32 tmr = IOP_TMR_EN | IOP_TMR_PRIVILEGED
+ | IOP_TMR_RELOAD | IOP_TMR_RATIO_1_1;
+
+ switch (mode) {
+ case CLOCK_EVT_MODE_PERIODIC:
+ write_tmr0(tmr & ~IOP_TMR_EN);
+ write_tcr0(ticks_per_jiffy - 1);
+ tmr |= (IOP_TMR_RELOAD | IOP_TMR_EN);
+ break;
+ case CLOCK_EVT_MODE_ONESHOT:
+ /* ->set_next_event sets period and enables timer */
+ tmr &= ~(IOP_TMR_RELOAD | IOP_TMR_EN);
+ break;
+ case CLOCK_EVT_MODE_RESUME:
+ tmr |= IOP_TMR_EN;
+ break;
+ case CLOCK_EVT_MODE_SHUTDOWN:
+ case CLOCK_EVT_MODE_UNUSED:
+ default:
+ tmr &= ~IOP_TMR_EN;
+ break;
+ }
+
+ write_tmr0(tmr);
+}
+
+static struct clock_event_device iop_clockevent = {
+ .name = "iop_timer0",
+ .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+ .rating = 300,
+ .shift = 20, /* ??? crude guesstimate */
+ .set_next_event = iop_set_next_event,
+ .set_mode = iop_set_mode,
+};
+
static unsigned long ticks_per_usec;
static unsigned long next_jiffy_time;
@@ -75,13 +132,12 @@ unsigned long iop_gettimeoffset(void)
static irqreturn_t
iop_timer_interrupt(int irq, void *dev_id)
{
+ struct clock_event_device *evt;
+
write_tisr(1);
- while ((signed long)(next_jiffy_time - read_tcr1())
- >= ticks_per_jiffy) {
- timer_tick();
- next_jiffy_time -= ticks_per_jiffy;
- }
+ evt = &iop_clockevent;
+ evt->event_handler(evt);
return IRQ_HANDLED;
}
@@ -112,10 +168,20 @@ void __init iop_init_time(unsigned long
IOP_TMR_RELOAD | IOP_TMR_RATIO_1_1;
/*
- * We use timer 0 for our timer interrupt, and timer 1 as
- * monotonic counter for tracking missed jiffies.
+ * Set up interrupting clockevent timer 0.
*/
+ write_tmr0(timer_ctl & ~IOP_TMR_EN);
+ setup_irq(IRQ_IOP_TIMER0, &iop_timer_irq);
+ iop_clockevent.mult =
+ div_sc(tick_rate, NSEC_PER_SEC, iop_clockevent.shift);
+ iop_clockevent.max_delta_ns =
+ clockevent_delta2ns(0xfffffffe, &iop_clockevent);
+ iop_clockevent.min_delta_ns =
+ clockevent_delta2ns(0xf, &iop_clockevent);
+ iop_clockevent.cpumask = cpumask_of(0);
+ clockevents_register_device(&iop_clockevent);
write_trr0(ticks_per_jiffy - 1);
+ write_tcr0(ticks_per_jiffy - 1);
write_tmr0(timer_ctl);
/*
@@ -128,6 +194,4 @@ void __init iop_init_time(unsigned long
clocksource_hz2mult(tick_rate,
iop_clocksource.shift);
clocksource_register(&iop_clocksource);
-
- setup_irq(IRQ_IOP_TIMER0, &iop_timer_irq);
}
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