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SubjectRe: [PATCH query] arm: i.MX/MX1 clock event source
Date
On Monday 22 January 2007 20:59, Ingo Molnar wrote:
> * Pavel Pisa <pisa@cmp.felk.cvut.cz> wrote:
> > Hello Thomas, Sascha and Ingo
> >
> > please can you find some time to review next patch
> > arm: i.MX/MX1 clock event source
> > which has been sent to you and to the ALKML at 2007-01-13.
> >
> > http://thread.gmane.org/gmane.linux.ports.arm.kernel/29510/focus=29533
> >
> > There seems to be some problems, because this patch has not been
> > accepted to patch-2.6.20-rc5-rt7.patch, but GENERIC_CLOCKEVENTS are
> > set already for i.MX and this results in a problems to run RT kernel
> > on this architecture.
>
> i've added your patch to -rt, but note that there's a new, slightly
> incompatible clockevents code in -rt now so you'll need to do some more
> (hopefully trivial) fixups for this to build and work.
>
> Ingo


Hello Ingo,

thanks for reply. I am attaching updated version of the patch at the end of e-mail.
There is problem with missing include in tick-sched.c

CC kernel/time/tick-sched.o
/usr/src/linux-2.6.20-rc5/kernel/time/tick-sched.c: In function `tick_nohz_handler':
/usr/src/linux-2.6.20-rc5/kernel/time/tick-sched.c:330: warning: implicit declaration of function `get_irq_regs'
/usr/src/linux-2.6.20-rc5/kernel/time/tick-sched.c:330: warning: initialization makes pointer from integer without a cast
/usr/src/linux-2.6.20-rc5/kernel/time/tick-sched.c: In function `tick_sched_timer':
/usr/src/linux-2.6.20-rc5/kernel/time/tick-sched.c:425: warning: initialization makes pointer from integer without a cast
LD kernel/time/built-in.o

--- linux-2.6.20-rc5.orig/kernel/time/tick-sched.c
+++ linux-2.6.20-rc5/kernel/time/tick-sched.c
@@ -20,6 +20,7 @@
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/tick.h>
+#include <asm/irq_regs.h>

#include "tick-internal.h"

And
CC arch/arm/kernel/process.o
/usr/src/linux-2.6.20-rc5/arch/arm/kernel/process.c: In function `cpu_idle':
/usr/src/linux-2.6.20-rc5/arch/arm/kernel/process.c:157: warning: implicit declaration of function `hrtimer_stop_sched_tick'
/usr/src/linux-2.6.20-rc5/arch/arm/kernel/process.c:161: warning: implicit declaration of function `hrtimer_restart_sched_tick'

--- linux-2.6.20-rc5.orig/arch/arm/kernel/process.c
+++ linux-2.6.20-rc5/arch/arm/kernel/process.c
@@ -154,11 +154,11 @@ void cpu_idle(void)
if (!idle)
idle = default_idle;
leds_event(led_idle_start);
- hrtimer_stop_sched_tick();
+ tick_nohz_stop_sched_tick();
while (!need_resched() && !need_resched_delayed())
idle();
leds_event(led_idle_end);
- hrtimer_restart_sched_tick();
+ tick_nohz_restart_sched_tick();
local_irq_disable();
__preempt_enable_no_resched();
__schedule();
Unfortunately, even with these corrections boot stuck at

Memory: 18972KB available (2488K code, 358K data, 92K init)

I have not time now to start JTAG debugging session, so I look at that
tomorrow or on Friday.

It seems, that the interrupts are not coming from device.

Best wishes

Pavel

==========================================================================
Subject: arm: i.MX/MX1 clock event source
Support clock event source based on i.MX general purpose
timer in free running timer mode.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>

arch/arm/mach-imx/time.c | 112 ++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 107 insertions(+), 5 deletions(-)
Index: linux-2.6.20-rc5/arch/arm/mach-imx/time.c
===================================================================
--- linux-2.6.20-rc5.orig/arch/arm/mach-imx/time.c
+++ linux-2.6.20-rc5/arch/arm/mach-imx/time.c
@@ -15,6 +15,9 @@
#include <linux/irq.h>
#include <linux/time.h>
#include <linux/clocksource.h>
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+#include <linux/clockchips.h>
+#endif

#include <asm/hardware.h>
#include <asm/io.h>
@@ -25,6 +28,11 @@
/* Use timer 1 as system timer */
#define TIMER_BASE IMX_TIM1_BASE

+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+static struct clock_event_device clockevent_imx;
+static enum clock_event_mode clockevent_mode = CLOCK_EVT_MODE_PERIODIC;
+#endif
+
static unsigned long evt_diff;

/*
@@ -33,6 +41,7 @@ static unsigned long evt_diff;
static irqreturn_t
imx_timer_interrupt(int irq, void *dev_id)
{
+ unsigned long tcmp;
uint32_t tstat;

/* clear the interrupt */
@@ -42,13 +51,20 @@ imx_timer_interrupt(int irq, void *dev_i
if (tstat & TSTAT_COMP) {
do {

+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+ if (clockevent_imx.event_handler)
+ clockevent_imx.event_handler(&clockevent_imx);
+ if (likely(clockevent_mode != CLOCK_EVT_MODE_PERIODIC))
+ break;
+#else
write_seqlock(&xtime_lock);
timer_tick();
write_sequnlock(&xtime_lock);
- IMX_TCMP(TIMER_BASE) += evt_diff;
+#endif
+ tcmp = IMX_TCMP(TIMER_BASE) + evt_diff;
+ IMX_TCMP(TIMER_BASE) = tcmp;

- } while (unlikely((int32_t)(IMX_TCMP(TIMER_BASE)
- - IMX_TCN(TIMER_BASE)) < 0));
+ } while (unlikely((int32_t)(tcmp - IMX_TCN(TIMER_BASE)) < 0));
}

return IRQ_HANDLED;
@@ -70,7 +86,7 @@ static void __init imx_timer_hardware_in
*/
IMX_TCTL(TIMER_BASE) = 0;
IMX_TPRER(TIMER_BASE) = 0;
- IMX_TCMP(TIMER_BASE) = LATCH - 1;
+ IMX_TCMP(TIMER_BASE) += LATCH;

IMX_TCTL(TIMER_BASE) = TCTL_FRR | TCTL_CLK_PCLK1 | TCTL_IRQEN | TCTL_TEN;
evt_diff = LATCH;
@@ -87,7 +103,7 @@ static struct clocksource clocksource_im
.read = imx_get_cycles,
.mask = 0xFFFFFFFF,
.shift = 20,
- .is_continuous = 1,
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int __init imx_clocksource_init(void)
@@ -99,11 +115,97 @@ static int __init imx_clocksource_init(v
return 0;
}

+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+
+static int imx_set_next_event(unsigned long evt,
+ struct clock_event_device *unused)
+{
+ unsigned long tcmp;
+ evt_diff = evt;
+
+ tcmp = IMX_TCN(TIMER_BASE) + evt;
+ IMX_TCMP(TIMER_BASE) = tcmp;
+
+ return unlikely((int32_t)(tcmp - IMX_TCN(TIMER_BASE)) < 0) ? -ETIME : 0;
+}
+
+static void imx_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 imx_set_next_event()
+ */
+ local_irq_save(flags);
+ /* Disable interrupt in GPT module */
+ IMX_TCTL(TIMER_BASE) &= ~TCTL_IRQEN;
+ if ((mode != CLOCK_EVT_MODE_PERIODIC) || (mode != clockevent_mode)) {
+ /* Set event time into far-far future */
+ IMX_TCMP(TIMER_BASE) = IMX_TCN(TIMER_BASE) - 3;
+ /* Clear pending interrupt */
+ IMX_TSTAT(TIMER_BASE) &= ~TSTAT_COMP;
+ }
+ /* Remember timer mode */
+ clockevent_mode = mode;
+ local_irq_restore(flags);
+
+ switch (mode) {
+ case CLOCK_EVT_MODE_PERIODIC:
+ /* It seems, that periodic mode expects old ugly latch period */
+ evt_diff = LATCH;
+ IMX_TCMP(TIMER_BASE) = IMX_TCN(TIMER_BASE) + evt_diff;
+ case CLOCK_EVT_MODE_ONESHOT:
+ /*
+ * Do not put overhead of interrupt enable/disable into
+ * imx_set_next_event(), the core has about 4 minutes
+ * to call imx_set_next_event() or shutdown clock after
+ * mode switching
+ */
+ local_irq_save(flags);
+ IMX_TCTL(TIMER_BASE) |= TCTL_IRQEN;
+ local_irq_restore(flags);
+ break;
+ case CLOCK_EVT_MODE_SHUTDOWN:
+ case CLOCK_EVT_MODE_UNUSED:
+ /* Left event sources disabled, no more interrupts appears */
+ break;
+ }
+}
+
+static struct clock_event_device clockevent_imx = {
+ .name = "imx_timer1",
+ .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+ .shift = 32,
+ .set_mode = imx_set_mode,
+ .set_next_event = imx_set_next_event,
+ .rating = 200,
+};
+
+static int __init imx_clockevent_init(void)
+{
+ clockevent_imx.mult = div_sc(imx_get_perclk1(), NSEC_PER_SEC,
+ clockevent_imx.shift);
+ clockevent_imx.max_delta_ns =
+ clockevent_delta2ns(0xfffffffe, &clockevent_imx);
+ clockevent_imx.min_delta_ns =
+ clockevent_delta2ns(0xf, &clockevent_imx);
+ clockevents_register_device(&clockevent_imx);
+
+ return 0;
+}
+#endif
+
+
static void __init imx_timer_init(void)
{
imx_timer_hardware_init();
imx_clocksource_init();

+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+ imx_clockevent_init();
+#endif
+
/*
* Make irqs happen for the system timer
*/
-
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