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Date:	Wed, 01 Sep 2010 12:30:11 -0700
From:	Alok Kataria <akataria@...are.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, apic: Add apic calibration hook.


On Fri, 2010-08-27 at 14:28 -0700, Alok Kataria wrote:
> Hi Thomas,
> 
> On Tue, 2010-08-24 at 14:58 -0700, Alok Kataria wrote:
> > On Tue, 2010-08-24 at 14:51 -0700, Thomas Gleixner wrote:
> > > On Tue, 24 Aug 2010, Alok Kataria wrote:
> > > > > > +
> > > > > > +		if (lapic_clockevent.mult)
> > > > > > +			return 0;
> > > > > 
> > > > >   Why is this necessary ? calibrate_APIC_clock() is only called once.
> > > > > 
> > > > 
> > > > Yes, though timer.calibrate_apci() could behave differently on different
> > > > platforms. For eg. the vmware_calibrate_apic doesn't initialize any of
> > > > the lapic_clockevent state and we need this to set it up in that case.
> > > 
> > > Can we please make this consistent ?
> 
> How does this patch look ? 

Thomas, any comments on the patch below, just want to make sure that
this didn't fell through the cracks.

Thanks,
Alok


> --
> 
> Add apic calibration hook.
> 
> From: Alok N Kataria <akataria@...are.com>
> 
> Add a new function ptr calibrate_apic to x86_init_ops structure. On native this
> does the usual apic calibration. On VMware's platform we override it with a
> routine which gets that information from the hypervisor.
> 
> Signed-off-by: Alok N Kataria <akataria@...are.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> ---
> 
>  arch/x86/include/asm/apic.h     |    6 +++
>  arch/x86/include/asm/x86_init.h |    2 +
>  arch/x86/kernel/apic/apic.c     |   88 ++++++++++++++++++++-------------------
>  arch/x86/kernel/cpu/vmware.c    |   30 ++++++++++++-
>  arch/x86/kernel/x86_init.c      |    1 
>  5 files changed, 82 insertions(+), 45 deletions(-)
> 
> 
> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> index 1fa03e0..5012ee5 100644
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -17,6 +17,10 @@
>  
>  #define ARCH_APICTIMER_STOPS_ON_C3	1
>  
> +/* Clock divisor */
> +#define APIC_DIVISOR	16
> +#define LAPIC_CAL_LOOPS	(HZ/10)
> +
>  /*
>   * Debugging macros
>   */
> @@ -238,6 +242,8 @@ extern void setup_boot_APIC_clock(void);
>  extern void setup_secondary_APIC_clock(void);
>  extern int APIC_init_uniprocessor(void);
>  extern void enable_NMI_through_LVT0(void);
> +extern int native_calibrate_apic(void);
> +extern int initialize_lapic(long delta, unsigned int calibration_result);
>  
>  /*
>   * On 32bit this is mach-xxx local
> diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
> index baa579c..58f982b 100644
> --- a/arch/x86/include/asm/x86_init.h
> +++ b/arch/x86/include/asm/x86_init.h
> @@ -83,11 +83,13 @@ struct x86_init_paging {
>   *				boot cpu
>   * @tsc_pre_init:		platform function called before TSC init
>   * @timer_init:			initialize the platform timer (default PIT/HPET)
> + * @calibrate_apic:		calibrate APIC bus freq (ticks per HZ)
>   */
>  struct x86_init_timers {
>  	void (*setup_percpu_clockev)(void);
>  	void (*tsc_pre_init)(void);
>  	void (*timer_init)(void);
> +	int (*calibrate_apic)(void);
>  };
>  
>  /**
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index e3b534c..ca5d084 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -176,7 +176,7 @@ static struct resource lapic_resource = {
>  	.flags = IORESOURCE_MEM | IORESOURCE_BUSY,
>  };
>  
> -static unsigned int calibration_result;
> +static unsigned int apic_calibration_res;
>  
>  static int lapic_next_event(unsigned long delta,
>  			    struct clock_event_device *evt);
> @@ -326,13 +326,6 @@ int lapic_get_maxlvt(void)
>  }
>  
>  /*
> - * Local APIC timer
> - */
> -
> -/* Clock divisor */
> -#define APIC_DIVISOR 16
> -
> -/*
>   * This function sets up the local APIC timer, with a timeout of
>   * 'clocks' APIC bus clock. During calibration we actually call
>   * this function twice on the boot CPU, once with a bogus timeout
> @@ -431,7 +424,7 @@ static void lapic_timer_setup(enum clock_event_mode mode,
>  	switch (mode) {
>  	case CLOCK_EVT_MODE_PERIODIC:
>  	case CLOCK_EVT_MODE_ONESHOT:
> -		__setup_APIC_LVTT(calibration_result,
> +		__setup_APIC_LVTT(apic_calibration_res,
>  				  mode != CLOCK_EVT_MODE_PERIODIC, 1);
>  		break;
>  	case CLOCK_EVT_MODE_UNUSED:
> @@ -500,8 +493,6 @@ static void __cpuinit setup_APIC_timer(void)
>   * back to normal later in the boot process).
>   */
>  
> -#define LAPIC_CAL_LOOPS		(HZ/10)
> -
>  static __initdata int lapic_cal_loops = -1;
>  static __initdata long lapic_cal_t1, lapic_cal_t2;
>  static __initdata unsigned long long lapic_cal_tsc1, lapic_cal_tsc2;
> @@ -590,13 +581,50 @@ calibrate_by_pmtimer(long deltapm, long *delta, long *deltatsc)
>  	return 0;
>  }
>  
> -static int __init calibrate_APIC_clock(void)
> +int __init initialize_lapic(long delta, unsigned int calibration_result)
> +{
> +	struct clock_event_device *levt = &__get_cpu_var(lapic_events);
> +
> +	/* Calculate the scaled math multiplication factor */
> +	lapic_clockevent.mult = div_sc(delta, TICK_NSEC * LAPIC_CAL_LOOPS,
> +				       lapic_clockevent.shift);
> +	lapic_clockevent.max_delta_ns =
> +		clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
> +	lapic_clockevent.min_delta_ns =
> +		clockevent_delta2ns(0xF, &lapic_clockevent);
> +
> +	apic_calibration_res = calibration_result;
> +
> +	apic_printk(APIC_VERBOSE, "..... delta %ld\n", delta);
> +	apic_printk(APIC_VERBOSE, "..... mult: %u\n", lapic_clockevent.mult);
> +	apic_printk(APIC_VERBOSE, "..... calibration result: %u\n",
> +		    calibration_result);
> +
> +	apic_printk(APIC_VERBOSE, "..... host bus clock speed is "
> +		    "%u.%04u MHz.\n",
> +		    calibration_result / (1000000 / HZ),
> +		    calibration_result % (1000000 / HZ));
> +
> +	/*
> +	 * Do a sanity check on the APIC calibration result
> +	 */
> +	if (calibration_result < (1000000 / HZ)) {
> +		pr_warning("APIC frequency too slow, disabling apic timer\n");
> +		return -1;
> +	}
> +
> +	levt->features &= ~CLOCK_EVT_FEAT_DUMMY;
> +	return 0;
> +}
> +
> +int __init native_calibrate_apic(void)
>  {
>  	struct clock_event_device *levt = &__get_cpu_var(lapic_events);
>  	void (*real_handler)(struct clock_event_device *dev);
>  	unsigned long deltaj;
>  	long delta, deltatsc;
>  	int pm_referenced = 0;
> +	unsigned int calibration_result;
>  
>  	local_irq_disable();
>  
> @@ -631,20 +659,12 @@ static int __init calibrate_APIC_clock(void)
>  	pm_referenced = !calibrate_by_pmtimer(lapic_cal_pm2 - lapic_cal_pm1,
>  					&delta, &deltatsc);
>  
> -	/* Calculate the scaled math multiplication factor */
> -	lapic_clockevent.mult = div_sc(delta, TICK_NSEC * LAPIC_CAL_LOOPS,
> -				       lapic_clockevent.shift);
> -	lapic_clockevent.max_delta_ns =
> -		clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
> -	lapic_clockevent.min_delta_ns =
> -		clockevent_delta2ns(0xF, &lapic_clockevent);
> -
>  	calibration_result = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;
>  
> -	apic_printk(APIC_VERBOSE, "..... delta %ld\n", delta);
> -	apic_printk(APIC_VERBOSE, "..... mult: %u\n", lapic_clockevent.mult);
> -	apic_printk(APIC_VERBOSE, "..... calibration result: %u\n",
> -		    calibration_result);
> +	if (initialize_lapic(delta, calibration_result)) {
> +		local_irq_enable();
> +		return -1;
> +	}
>  
>  	if (cpu_has_tsc) {
>  		apic_printk(APIC_VERBOSE, "..... CPU clock speed is "
> @@ -653,22 +673,6 @@ static int __init calibrate_APIC_clock(void)
>  			    (deltatsc / LAPIC_CAL_LOOPS) % (1000000 / HZ));
>  	}
>  
> -	apic_printk(APIC_VERBOSE, "..... host bus clock speed is "
> -		    "%u.%04u MHz.\n",
> -		    calibration_result / (1000000 / HZ),
> -		    calibration_result % (1000000 / HZ));
> -
> -	/*
> -	 * Do a sanity check on the APIC calibration result
> -	 */
> -	if (calibration_result < (1000000 / HZ)) {
> -		local_irq_enable();
> -		pr_warning("APIC frequency too slow, disabling apic timer\n");
> -		return -1;
> -	}
> -
> -	levt->features &= ~CLOCK_EVT_FEAT_DUMMY;
> -
>  	/*
>  	 * PM timer calibration failed or not turned on
>  	 * so lets try APIC timer based calibration
> @@ -706,7 +710,7 @@ static int __init calibrate_APIC_clock(void)
>  
>  	if (levt->features & CLOCK_EVT_FEAT_DUMMY) {
>  		pr_warning("APIC timer disabled due to verification failure\n");
> -			return -1;
> +		return -1;
>  	}
>  
>  	return 0;
> @@ -738,7 +742,7 @@ void __init setup_boot_APIC_clock(void)
>  	apic_printk(APIC_VERBOSE, "Using local APIC timer interrupts.\n"
>  		    "calibrating APIC timer ...\n");
>  
> -	if (calibrate_APIC_clock()) {
> +	if (x86_init.timers.calibrate_apic()) {
>  		/* No broadcast on UP ! */
>  		if (num_possible_cpus() > 1)
>  			setup_APIC_timer();
> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
> index 227b044..e8b760e 100644
> --- a/arch/x86/kernel/cpu/vmware.c
> +++ b/arch/x86/kernel/cpu/vmware.c
> @@ -26,6 +26,7 @@
>  #include <asm/div64.h>
>  #include <asm/x86_init.h>
>  #include <asm/hypervisor.h>
> +#include <asm/apic.h>
>  
>  #define CPUID_VMWARE_INFO_LEAF	0x40000000
>  #define VMWARE_HYPERVISOR_MAGIC	0x564D5868
> @@ -72,17 +73,40 @@ static unsigned long vmware_get_tsc_khz(void)
>  	return tsc_hz;
>  }
>  
> +static int __init vmware_calibrate_apic(void)
> +{
> +	unsigned int calibration_result;
> +	uint32_t eax, ebx, ecx, edx;
> +	int err;
> +	long delta;
> +	unsigned long flags;
> +
> +	VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
> +	BUG_ON(!ecx);
> +	calibration_result = ecx / HZ;
> +
> +	printk(KERN_INFO "APIC bus freq read from hypervisor\n");
> +
> +	delta  = (calibration_result * LAPIC_CAL_LOOPS) / APIC_DIVISOR;
> +	local_irq_save(flags);
> +	err = initialize_lapic(delta, calibration_result);
> +	local_irq_restore(flags);
> +
> +	return err;
> +}
> +
>  static void __init vmware_platform_setup(void)
>  {
>  	uint32_t eax, ebx, ecx, edx;
>  
>  	VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
>  
> -	if (ebx != UINT_MAX)
> +	if (ebx != UINT_MAX) {
>  		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
> -	else
> +		x86_init.timers.calibrate_apic = vmware_calibrate_apic;
> +	} else
>  		printk(KERN_WARNING
> -		       "Failed to get TSC freq from the hypervisor\n");
> +		       "Failed to setup VMware hypervisor platform\n");
>  }
>  
>  /*
> diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
> index cd6da6b..f162e14 100644
> --- a/arch/x86/kernel/x86_init.c
> +++ b/arch/x86/kernel/x86_init.c
> @@ -68,6 +68,7 @@ struct x86_init_ops x86_init __initdata = {
>  		.setup_percpu_clockev	= setup_boot_APIC_clock,
>  		.tsc_pre_init		= x86_init_noop,
>  		.timer_init		= hpet_time_init,
> +		.calibrate_apic		= native_calibrate_apic
>  	},
>  
>  	.iommu = {
> 

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