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    SubjectRe: [PATCH] ARM: smp_twd: Reconfigure clockevents after cpufreq change
    From
    2011/5/17 Colin Cross <ccross@android.com>:

    > This patch depends on Thomas Gleixner's patch to add clockevents_reconfigure
    > See: https://lkml.org/lkml/2011/5/13/122

    Patch set has evolved, see below.
    Also note that you more or less reimplement Rob Herrings patch:
    http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6802/1
    (no big deal I guess, give him a nod)

    To work with Thomas full changeset just create a fresh branch and:
    git pull git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-tip.git
    timers/clockevents

    Pls change subject from ARM: to clockevents: and merge through
    Thomas tree (IMHO).

    > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
    > index 60636f4..dbf58d4 100644
    > --- a/arch/arm/kernel/smp_twd.c
    > +++ b/arch/arm/kernel/smp_twd.c
    > @@ -10,21 +10,29 @@
    >  */
    >  #include <linux/init.h>
    >  #include <linux/kernel.h>
    > +#include <linux/clk.h>
    > +#include <linux/cpufreq.h>
    >  #include <linux/delay.h>
    >  #include <linux/device.h>
    > +#include <linux/err.h>
    >  #include <linux/smp.h>
    >  #include <linux/jiffies.h>
    >  #include <linux/clockchips.h>
    >  #include <linux/irq.h>
    >  #include <linux/io.h>
    > +#include <linux/percpu.h>
    >
    >  #include <asm/smp_twd.h>
    >  #include <asm/hardware/gic.h>
    >
    > +#define TWD_MIN_RANGE 4
    > +

    Loose this. Let the framework decide using the function below.

    >  /* set up by the platform code */
    >  void __iomem *twd_base;
    >
    > +static struct clk *twd_clk;
    >  static unsigned long twd_timer_rate;
    > +static DEFINE_PER_CPU(struct clock_event_device *, twd_ce);
    >
    >  static void twd_set_mode(enum clock_event_mode mode,
    >                        struct clock_event_device *clk)
    > @@ -80,6 +88,49 @@ int twd_timer_ack(void)
    >        return 0;
    >  }
    >
    > +/*
    > + * Updates clockevent frequency when the cpu frequency changes.
    > + * Called on the cpu that is changing frequency with interrupts disabled.
    > + */
    > +static void twd_update_frequency(void *data)
    > +{
    > +       twd_timer_rate = clk_get_rate(twd_clk);
    > +
    > +       clockevents_reconfigure(__get_cpu_var(twd_ce), twd_timer_rate,
    > +                       TWD_MIN_RANGE);

    Changed name to clockevents_update_freq(), dropped range argument.

    > +}
    > +
    > +static int twd_cpufreq_transition(struct notifier_block *nb,
    > +       unsigned long state, void *data)
    > +{
    > +       struct cpufreq_freqs *freqs = data;
    > +
    > +       /*
    > +        * The twd clock events must be reprogrammed to account for the new
    > +        * frequency.  The timer is local to a cpu, so cross-call to the
    > +        * changing cpu.
    > +        */
    > +       if (state == CPUFREQ_POSTCHANGE || state == CPUFREQ_RESUMECHANGE)
    > +               smp_call_function_single(freqs->cpu, twd_update_frequency,
    > +                       NULL, 1);
    > +
    > +       return NOTIFY_OK;
    > +}
    > +
    > +static struct notifier_block twd_cpufreq_nb = {
    > +       .notifier_call = twd_cpufreq_transition,
    > +};
    > +
    > +static int twd_cpufreq_init(void)
    > +{
    > +       if (!IS_ERR_OR_NULL(twd_clk))
    > +               return cpufreq_register_notifier(&twd_cpufreq_nb,
    > +                       CPUFREQ_TRANSITION_NOTIFIER);
    > +
    > +       return 0;
    > +}
    > +core_initcall(twd_cpufreq_init);
    > +
    >  static void __cpuinit twd_calibrate_rate(void)
    >  {
    >        unsigned long count;
    > @@ -124,7 +175,16 @@ static void __cpuinit twd_calibrate_rate(void)
    >  */
    >  void __cpuinit twd_timer_setup(struct clock_event_device *clk)
    >  {
    > -       twd_calibrate_rate();
    > +       if (twd_clk == NULL) {
    > +               twd_clk = clk_get_sys("smp_twd", NULL);
    > +               if (IS_ERR_OR_NULL(twd_clk))
    > +                       pr_warn("%s: no clock found\n", __func__);
    > +       }
    > +
    > +       if (!IS_ERR_OR_NULL(twd_clk))
    > +               twd_timer_rate = clk_get_rate(twd_clk);
    > +       else
    > +               twd_calibrate_rate();
    >
    >        clk->name = "local_timer";
    >        clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
    > @@ -132,13 +192,16 @@ void __cpuinit twd_timer_setup(struct clock_event_device *clk)
    >        clk->rating = 350;
    >        clk->set_mode = twd_set_mode;
    >        clk->set_next_event = twd_set_next_event;
    > -       clk->shift = 20;
    > -       clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
    > +
    > +       clockevents_calc_mult_shift(clk, twd_timer_rate, TWD_MIN_RANGE);
    > +
    >        clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
    >        clk->min_delta_ns = clockevent_delta2ns(0xf, clk);

    Get rid of everything between clk->shift ... and here and replace it with:

    clockevents_config_and_register(clk, twd_timer_rate,
    0xf, 0xffffffff);

    >        /* Make sure our local interrupt controller has this enabled */
    >        gic_enable_ppi(clk->irq);
    >
    > +       __get_cpu_var(twd_ce) = clk;
    > +
    >        clockevents_register_device(clk);
    >  }


    Or just smack in this patch on top:

    From fd546090b8f0cb5df06103c014466c86cf58b73a Mon Sep 17 00:00:00 2001
    From: Linus Walleij <linus.walleij@stericsson.com>
    Date: Thu, 19 May 2011 18:55:22 +0200
    Subject: [PATCH] Fix smallish cleanup

    ---
    arch/arm/kernel/smp_twd.c | 13 +++----------
    1 files changed, 3 insertions(+), 10 deletions(-)

    diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
    index dbf58d4..968f298 100644
    --- a/arch/arm/kernel/smp_twd.c
    +++ b/arch/arm/kernel/smp_twd.c
    @@ -25,8 +25,6 @@
    #include <asm/smp_twd.h>
    #include <asm/hardware/gic.h>

    -#define TWD_MIN_RANGE 4
    -
    /* set up by the platform code */
    void __iomem *twd_base;

    @@ -96,8 +94,7 @@ static void twd_update_frequency(void *data)
    {
    twd_timer_rate = clk_get_rate(twd_clk);

    - clockevents_reconfigure(__get_cpu_var(twd_ce), twd_timer_rate,
    - TWD_MIN_RANGE);
    + clockevents_update_freq(__get_cpu_var(twd_ce), twd_timer_rate);
    }

    static int twd_cpufreq_transition(struct notifier_block *nb,
    @@ -193,15 +190,11 @@ void __cpuinit twd_timer_setup(struct
    clock_event_device *clk)
    clk->set_mode = twd_set_mode;
    clk->set_next_event = twd_set_next_event;

    - clockevents_calc_mult_shift(clk, twd_timer_rate, TWD_MIN_RANGE);
    -
    - clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
    - clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
    -
    /* Make sure our local interrupt controller has this enabled */
    gic_enable_ppi(clk->irq);

    __get_cpu_var(twd_ce) = clk;

    - clockevents_register_device(clk);
    + clockevents_config_and_register(clk, twd_timer_rate,
    + 0xf, 0xffffffff);
    }
    --
    1.7.3.2

    With these changes (provided they work) all should be well, so:
    Tested-by: Linus Walleij <linus.walleij@linaro.org>

    If all is well on your side as well, ask Thomas to take this into the
    timers/clockevents branch where all dependencies are.

    Yours,
    Linus Walleij
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