Commit 60dbd663 authored by Jesper Nilsson's avatar Jesper Nilsson
Browse files

CRIS: GENERIC_TIME fixes 



GENERIC_TIME was not functional for CRIS, giving random backward
time jumps.

For CRISv32 implement a new clocksource using the free running counter
and ditch the arch_gettimeoffset.

The random time jumps still existed, but turned out to be the write_seqlock
which was missing around our do_timer() call.

So switch over to GENERIC_TIME using the clocksource for CRISv32.

CRISv10 doesn't have the free running counter needed for the
clocksource trick, but we can still use GENERIC_TIME with
arch_gettimeoffset.

Unfortunately, there were problems in using the prescaler register
to timer0 for the gettimeoffset calculation, so it is now ignored,
making our resolution worse by the tune of 40usec (0.4%) worst case.

At the same time, clean up some formatting and use NSEC_PER_SEC
instead of 1000000000.

Signed-off-by: default avatarJesper Nilsson <jesper.nilsson@axis.com>
parent 26bfeea3

arch/cris/Kconfig

+4 −1
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ config GENERIC_CMOS_UPDATE 
	def_bool y



config ARCH_USES_GETTIMEOFFSET

	def_bool y

	def_bool n



config GENERIC_IOMAP

       bool
@@ -131,16 +131,19 @@ choice 


config ETRAX100LX

	bool "ETRAX-100LX-v1"

	select ARCH_USES_GETTIMEOFFSET

	help

	  Support version 1 of the ETRAX 100LX.



config ETRAX100LX_V2

	bool "ETRAX-100LX-v2"

	select ARCH_USES_GETTIMEOFFSET

	help

	  Support version 2 of the ETRAX 100LX.



config SVINTO_SIM

	bool "ETRAX-100LX-for-xsim-simulator"

	select ARCH_USES_GETTIMEOFFSET

	help

	  Support the xsim ETRAX Simulator.

arch/cris/arch-v10/kernel/time.c

+2 −52
Original line number Diff line number Diff line
@@ -61,66 +61,16 @@ unsigned long get_ns_in_jiffie(void) 


unsigned long do_slow_gettimeoffset(void)

{

	unsigned long count, t1;

	unsigned long usec_count = 0;

	unsigned short presc_count;



	static unsigned long count_p = TIMER0_DIV;/* for the first call after boot */

	static unsigned long jiffies_p = 0;



	/*

	 * cache volatile jiffies temporarily; we have IRQs turned off. 

	 */

	unsigned long jiffies_t;

	unsigned long count;



	/* The timer interrupt comes from Etrax timer 0. In order to get

	 * better precision, we check the current value. It might have

	 * underflowed already though.

	 */



#ifndef CONFIG_SVINTO_SIM

	/* Not available in the xsim simulator. */

	count = *R_TIMER0_DATA;

	presc_count = *R_TIM_PRESC_STATUS;  

	/* presc_count might be wrapped */

	t1 = *R_TIMER0_DATA;

	if (count != t1){

		/* it wrapped, read prescaler again...  */

		presc_count = *R_TIM_PRESC_STATUS;

		count = t1;

	}

#else

	count = 0;

	presc_count = 0;

#endif



 	jiffies_t = jiffies;



	/*

	 * avoiding timer inconsistencies (they are rare, but they happen)...

	 * there are one problem that must be avoided here:

	 *  1. the timer counter underflows

	 */

	if( jiffies_t == jiffies_p ) {

		if( count > count_p ) {

			/* Timer wrapped, use new count and prescale 

			 * increase the time corresponding to one jiffie

			 */

			usec_count = 1000000/HZ;

		}

	} else

		jiffies_p = jiffies_t;

        count_p = count;

	if (presc_count >= PRESCALE_VALUE/2 ){

		presc_count =  PRESCALE_VALUE - presc_count + PRESCALE_VALUE/2;

	} else {

		presc_count =  PRESCALE_VALUE - presc_count - PRESCALE_VALUE/2;

	}

	/* Convert timer value to usec */

	usec_count += ( (TIMER0_DIV - count) * (1000000/HZ)/TIMER0_DIV ) +

	              (( (presc_count) * (1000000000/PRESCALE_FREQ))/1000);



	return usec_count;

	return (TIMER0_DIV - count) * ((NSEC_PER_SEC/1000)/HZ)/TIMER0_DIV;

}



/* Excerpt from the Etrax100 HSDD about the built-in watchdog:

arch/cris/arch-v32/kernel/time.c

+34 −51
Original line number Diff line number Diff line 
/*

 *  linux/arch/cris/arch-v32/kernel/time.c

 *

 *  Copyright (C) 2003-2007 Axis Communications AB

 *  Copyright (C) 2003-2010 Axis Communications AB

 *

 */



#include <linux/timex.h>

#include <linux/time.h>

#include <linux/jiffies.h>

#include <linux/clocksource.h>

#include <linux/interrupt.h>

#include <linux/swap.h>

#include <linux/sched.h>
@@ -36,6 +36,30 @@ 
/* Number of 763 counts before watchdog bites */

#define ETRAX_WD_CNT		((2*ETRAX_WD_HZ)/HZ + 1)



/* Register the continuos readonly timer available in FS and ARTPEC-3.  */

static cycle_t read_cont_rotime(struct clocksource *cs)

{

	return (u32)REG_RD(timer, regi_timer0, r_time);

}



static struct clocksource cont_rotime = {

	.name   = "crisv32_rotime",

	.rating = 300,

	.read   = read_cont_rotime,

	.mask   = CLOCKSOURCE_MASK(32),

	.shift  = 10,

	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,

};



static int __init etrax_init_cont_rotime(void)

{

	cont_rotime.mult = clocksource_khz2mult(100000, cont_rotime.shift);

	clocksource_register(&cont_rotime);

	return 0;

}

arch_initcall(etrax_init_cont_rotime);





unsigned long timer_regs[NR_CPUS] =

{

	regi_timer0,
@@ -67,43 +91,6 @@ unsigned long get_ns_in_jiffie(void) 
	return ns;

}



unsigned long do_slow_gettimeoffset(void)

{

	unsigned long count;

	unsigned long usec_count = 0;



	/* For the first call after boot */

	static unsigned long count_p = TIMER0_DIV;

	static unsigned long jiffies_p = 0;



	/* Cache volatile jiffies temporarily; we have IRQs turned off. */

	unsigned long jiffies_t;



	/* The timer interrupt comes from Etrax timer 0. In order to get

	 * better precision, we check the current value. It might have

	 * underflowed already though. */

	count = REG_RD(timer, regi_timer0, r_tmr0_data);

	jiffies_t = jiffies;



	/* Avoiding timer inconsistencies (they are rare, but they happen)

	 * There is one problem that must be avoided here:

	 *	1. the timer counter underflows

	 */

	if( jiffies_t == jiffies_p ) {

		if( count > count_p ) {

			/* Timer wrapped, use new count and prescale.

			 * Increase the time corresponding to one jiffy.

			 */

			usec_count = 1000000/HZ;

		}

	} else

		jiffies_p = jiffies_t;

        count_p = count;

	/* Convert timer value to usec */

	/* 100 MHz timer, divide by 100 to get usec */

	usec_count +=  (TIMER0_DIV - count) / 100;

	return usec_count;

}



/* From timer MDS describing the hardware watchdog:

 * 4.3.1 Watchdog Operation
@@ -126,8 +113,7 @@ static short int watchdog_key = 42; /* arbitrary 7 bit number */ 
 * is used though, so set this really low. */

#define WATCHDOG_MIN_FREE_PAGES 8



void

reset_watchdog(void)

void reset_watchdog(void)

{

#if defined(CONFIG_ETRAX_WATCHDOG)

	reg_timer_rw_wd_ctrl wd_ctrl = { 0 };
@@ -147,8 +133,7 @@ reset_watchdog(void) 


/* stop the watchdog - we still need the correct key */



void

stop_watchdog(void)

void stop_watchdog(void)

{

#if defined(CONFIG_ETRAX_WATCHDOG)

	reg_timer_rw_wd_ctrl wd_ctrl = { 0 };
@@ -162,8 +147,7 @@ stop_watchdog(void) 


extern void show_registers(struct pt_regs *regs);



void

handle_watchdog_bite(struct pt_regs* regs)

void handle_watchdog_bite(struct pt_regs *regs)

{

#if defined(CONFIG_ETRAX_WATCHDOG)

	extern int cause_of_death;
@@ -203,8 +187,7 @@ handle_watchdog_bite(struct pt_regs* regs) 
 */

extern void cris_do_profile(struct pt_regs *regs);



static inline irqreturn_t

timer_interrupt(int irq, void *dev_id)

static inline irqreturn_t timer_interrupt(int irq, void *dev_id)

{

	struct pt_regs *regs = get_irq_regs();

	int cpu = smp_processor_id();
@@ -233,7 +216,9 @@ timer_interrupt(int irq, void *dev_id) 
		return IRQ_HANDLED;



	/* Call the real timer interrupt handler */

	write_seqlock(&xtime_lock);

	do_timer(1);

	write_sequnlock(&xtime_lock);

        return IRQ_HANDLED;

}
@@ -246,8 +231,7 @@ static struct irqaction irq_timer = { 
	.name = "timer"

};



void __init

cris_timer_init(void)

void __init cris_timer_init(void)

{

	int cpu = smp_processor_id();

	reg_timer_rw_tmr0_ctrl tmr0_ctrl = { 0 };
@@ -273,8 +257,7 @@ cris_timer_init(void) 
	REG_WR(timer, timer_regs[cpu], rw_intr_mask, timer_intr_mask);

}



void __init

time_init(void)

void __init time_init(void)

{

	reg_intr_vect_rw_mask intr_mask;

arch/cris/kernel/time.c

+5 −2
Original line number Diff line number Diff line
@@ -39,6 +39,8 @@ int have_rtc; /* used to remember if we have an RTC or not */; 
extern unsigned long loops_per_jiffy; /* init/main.c */

unsigned long loops_per_usec;





#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET

extern unsigned long do_slow_gettimeoffset(void);

static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset;
@@ -46,6 +48,7 @@ u32 arch_gettimeoffset(void) 
{

       return do_gettimeoffset() * 1000;

}

#endif



/*

 * BUG: This routine does not handle hour overflow properly; it just
@@ -151,7 +154,7 @@ cris_do_profile(struct pt_regs* regs) 


unsigned long long sched_clock(void)

{

	return (unsigned long long)jiffies * (1000000000 / HZ) +

	return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ) +

		get_ns_in_jiffie();

}

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