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Message-Id: <8E44DB06-767D-4864-8D2C-6132E4D4370B@kernel.crashing.org>
Date: Thu, 17 May 2007 12:47:42 -0500
From: Kumar Gala <galak@...nel.crashing.org>
To: Sergei Shtylyov <sshtylyov@...mvista.com>
Cc: tglx@...utronix.de, mingo@...e.hu, linuxppc-dev@...abs.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver
On May 17, 2007, at 12:42 PM, Sergei Shtylyov wrote:
> Add PowerPC decrementer clock event driver.
>
> Every effort has been made to support the different implementations
> of the
> decrementer: the classic one (with 970 series variation), 40x and
> Book E
> specific ones.
>
> I had to make CONFIG_GENERIC_CLOCKEVENTS option selectable for the
> compatibility reasons -- this option is not compatible with the PPC64
> deterministic time accounting.
>
> Thanks to Daniel Walker and Thomas Gleixner for the suggestions
> they made...
>
> Signed-off-by: Sergei Shtylyov <sshtylyov@...mvista.com>
>
> ---
> This patch has been reworked against the 2.6.21 clockevents framework.
> It has only been tested on the Book E 32-bit CPU this time, so re-
> testing on
> "classic" PowerPC CPUs is needed (used to work as of 2.6.18-rt7)...
>
> CONFIG_PPC_MULTIPLATFORM was the best option I was able to come up
> with
> to cover machines built on 970 series CPUs...
>
> arch/powerpc/Kconfig | 12 +++-
> arch/powerpc/kernel/time.c | 124 +++++++++++++++++++++++++++++++++
> +++++++++++-
> 2 files changed, 134 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/arch/powerpc/Kconfig
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/Kconfig
> +++ linux-2.6/arch/powerpc/Kconfig
> @@ -317,7 +317,7 @@ config PPC_STD_MMU_32
>
> config VIRT_CPU_ACCOUNTING
> bool "Deterministic task and CPU time accounting"
> - depends on PPC64
> + depends on PPC64 && !GENERIC_CLOCKEVENTS
> default y
> help
> Select this option to enable more accurate task and CPU time
> @@ -760,6 +760,16 @@ config HIGHMEM
> depends on PPC32
>
> source kernel/Kconfig.hz
> +
> +config GENERIC_CLOCKEVENTS
> + bool "Clock event devices support"
> + default n
> + help
> + Enable support for the clock event devices necessary for the
> + high-resolution timers and the tickless system support.
> + NOTE: This is not compatible with the deterministic time
> accounting
> + option on PPC64.
> +
> source kernel/Kconfig.preempt
>
> config RWSEM_GENERIC_SPINLOCK
> Index: linux-2.6/arch/powerpc/kernel/time.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/kernel/time.c
> +++ linux-2.6/arch/powerpc/kernel/time.c
> @@ -52,6 +52,7 @@
> #include <linux/jiffies.h>
> #include <linux/posix-timers.h>
> #include <linux/irq.h>
> +#include <linux/clockchips.h>
>
> #include <asm/io.h>
> #include <asm/processor.h>
> @@ -128,6 +129,83 @@ unsigned long ppc_tb_freq;
> static u64 tb_last_jiffy __cacheline_aligned_in_smp;
> static DEFINE_PER_CPU(u64, last_jiffy);
>
> +#ifdef CONFIG_GENERIC_CLOCKEVENTS
> +
> +#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
> +#define DECREMENTER_MAX 0xffffffff
> +#else
> +#define DECREMENTER_MAX 0x7fffffff /* setting MSB triggers an
> interrupt */
> +#endif
> +
> +static int decrementer_set_next_event(unsigned long evt,
> + struct clock_event_device *dev)
> +{
> +#if defined(CONFIG_40x)
> + mtspr(SPRN_PIT, evt); /* 40x has a hidden PIT auto-reload
> register */
> +#elif defined(CONFIG_BOOKE)
> + mtspr(SPRN_DECAR, evt); /* Book E has separate auto-reload
> register */
> + set_dec(evt);
what's the point of setting decar if you're just going to set_dec as
well?
> +#else
> + set_dec(evt - 1); /* Classic decrementer interrupts at -1 */
> +#endif
> + return 0;
> +}
> +
> +static void decrementer_set_mode(enum clock_event_mode mode,
> + struct clock_event_device *dev)
> +{
> +#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
> + u32 tcr = mfspr(SPRN_TCR);
> +
> + tcr |= TCR_DIE;
> + switch (mode) {
> + case CLOCK_EVT_MODE_PERIODIC:
> + tcr |= TCR_ARE;
> + break;
> + case CLOCK_EVT_MODE_ONESHOT:
> + tcr &= ~TCR_ARE;
> + break;
> + case CLOCK_EVT_MODE_UNUSED:
> + case CLOCK_EVT_MODE_SHUTDOWN:
> + tcr &= ~TCR_DIE;
> + break;
> + }
> + mtspr(SPRN_TCR, tcr);
> +#endif
> + if (mode == CLOCK_EVT_MODE_PERIODIC)
> + decrementer_set_next_event(tb_ticks_per_jiffy, dev);
> +}
> +
> +static struct clock_event_device decrementer_clockevent = {
> + .name = "decrementer",
> +#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
> + .features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
> +#else
> + .features = CLOCK_EVT_FEAT_ONESHOT,
> +#endif
> + .shift = 32,
> + .rating = 200,
> + .irq = -1,
> + .set_next_event = decrementer_set_next_event,
> + .set_mode = decrementer_set_mode,
> +};
> +
> +static DEFINE_PER_CPU(struct clock_event_device, decrementers);
> +
> +static void register_decrementer(void)
> +{
> + int cpu = smp_processor_id();
> + struct clock_event_device *decrementer = &per_cpu(decrementers,
> cpu);
> +
> + memcpy(decrementer, &decrementer_clockevent, sizeof(*decrementer));
> +
> + decrementer->cpumask = cpumask_of_cpu(cpu);
> +
> + clockevents_register_device(decrementer);
> +}
> +
> +#endif /* CONFIG_GENERIC_CLOCKEVENTS */
> +
> #ifdef CONFIG_VIRT_CPU_ACCOUNTING
> /*
> * Factors for converting from cputime_t (timebase ticks) to
> @@ -313,6 +391,9 @@ void snapshot_timebase(void)
> {
> __get_cpu_var(last_jiffy) = get_tb();
> snapshot_purr();
> +#ifdef CONFIG_GENERIC_CLOCKEVENTS
> + register_decrementer();
> +#endif
> }
>
> void __delay(unsigned long loops)
> @@ -470,7 +551,31 @@ void timer_interrupt(struct pt_regs * re
> old_regs = set_irq_regs(regs);
> irq_enter();
>
> +#ifdef CONFIG_GENERIC_CLOCKEVENTS
> +#ifdef CONFIG_PPC_MULTIPLATFORM
> + /*
> + * We must write a positive value to the decrementer to clear
> + * the interrupt on the IBM 970 CPU series. In periodic mode,
> + * this happens when the decrementer gets reloaded later, but
> + * in one-shot mode, we have to do it here since an event handler
> + * may skip loading the new value...
> + */
> + if (per_cpu(decrementers, cpu).mode != CLOCK_EVT_MODE_PERIODIC)
> + set_dec(DECREMENTER_MAX);
> +#endif
> + /*
> + * We can't disable the decrementer, so in the period between
> + * CPU being marked offline and calling stop-self, it's taking
> + * timer interrupts...
> + */
> + if (!cpu_is_offline(cpu)) {
> + struct clock_event_device *dev = &per_cpu(decrementers, cpu);
> +
> + dev->event_handler(dev);
> + }
> +#else
> profile_tick(CPU_PROFILING);
> +#endif
> calculate_steal_time();
>
> #ifdef CONFIG_PPC_ISERIES
> @@ -486,6 +591,7 @@ void timer_interrupt(struct pt_regs * re
> if (__USE_RTC() && per_cpu(last_jiffy, cpu) >= 1000000000)
> per_cpu(last_jiffy, cpu) -= 1000000000;
>
> +#ifndef CONFIG_GENERIC_CLOCKEVENTS
> /*
> * We cannot disable the decrementer, so in the period
> * between this cpu's being marked offline in cpu_online_map
> @@ -495,6 +601,7 @@ void timer_interrupt(struct pt_regs * re
> */
> if (!cpu_is_offline(cpu))
> account_process_time(regs);
> +#endif
>
> /*
> * No need to check whether cpu is offline here; boot_cpuid
> @@ -507,15 +614,19 @@ void timer_interrupt(struct pt_regs * re
> tb_next_jiffy = tb_last_jiffy + tb_ticks_per_jiffy;
> if (per_cpu(last_jiffy, cpu) >= tb_next_jiffy) {
> tb_last_jiffy = tb_next_jiffy;
> +#ifndef CONFIG_GENERIC_CLOCKEVENTS
> do_timer(1);
> +#endif
> /*timer_recalc_offset(tb_last_jiffy);*/
> timer_check_rtc();
> }
> write_sequnlock(&xtime_lock);
> }
> -
> +
> +#ifndef CONFIG_GENERIC_CLOCKEVENTS
> next_dec = tb_ticks_per_jiffy - ticks;
> set_dec(next_dec);
> +#endif
>
> #ifdef CONFIG_PPC_ISERIES
> if (firmware_has_feature(FW_FEATURE_ISERIES) &&
> hvlpevent_is_pending())
> @@ -770,8 +881,19 @@ void __init time_init(void)
> -xtime.tv_sec, -xtime.tv_nsec);
> write_sequnlock_irqrestore(&xtime_lock, flags);
>
> +#ifdef CONFIG_GENERIC_CLOCKEVENTS
> + decrementer_clockevent.mult = div_sc(ppc_tb_freq, NSEC_PER_SEC,
> + decrementer_clockevent.shift);
> + decrementer_clockevent.max_delta_ns =
> + clockevent_delta2ns(DECREMENTER_MAX, &decrementer_clockevent);
> + decrementer_clockevent.min_delta_ns =
> + clockevent_delta2ns(0xf, &decrementer_clockevent);
> +
> + register_decrementer();
> +#else
> /* Not exact, but the timer interrupt takes care of this */
> set_dec(tb_ticks_per_jiffy);
> +#endif
> }
>
> #define FEBRUARY 2
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@...abs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
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