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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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