Re: [PATCH] ARM: smp_twd: Reconfigure clockevents after cpufreq change
From: Colin Cross
Date: Thu May 19 2011 - 19:26:42 EST
On Thu, May 19, 2011 at 10:32 AM, Linus Walleij
<linus.walleij@xxxxxxxxxx> wrote:
> 2011/5/17 Colin Cross <ccross@xxxxxxxxxxx>:
>
>> 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).
I don't think the subject should change - the patch is to ARM code,
not clockevent code, it's named for what the patch does, not whose
tree it goes through.
>> 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@xxxxxxxxxxxxxx>
> 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@xxxxxxxxxx>
Thanks, I'll squash your fixes in.
> 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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