xref: /netbsd-src/sys/arch/arm/footbridge/footbridge_clock.c (revision 77e75c280a6ef9de02ed9c7c1ed432312348a840)

/*	$NetBSD: footbridge_clock.c,v 1.27 2021/08/13 11:40:43 skrll Exp $	*/

/*
 * Copyright (c) 1997 Mark Brinicombe.
 * Copyright (c) 1997 Causality Limited.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by Mark Brinicombe
 *	for the NetBSD Project.
 * 4. The name of the company nor the name of the author may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: footbridge_clock.c,v 1.27 2021/08/13 11:40:43 skrll Exp $");

/* Include header files */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/time.h>
#include <sys/timetc.h>
#include <sys/device.h>

#include <machine/intr.h>

#include <arm/cpufunc.h>

#include <arm/footbridge/dc21285reg.h>
#include <arm/footbridge/footbridgevar.h>
#include <arm/footbridge/footbridge.h>

extern struct footbridge_softc *clock_sc;
extern u_int dc21285_fclk;

int clockhandler(void *);
int statclockhandler(void *);
static int load_timer(int, int);

/*
 * Statistics clock variance, in usec.  Variance must be a
 * power of two.  Since this gives us an even number, not an odd number,
 * we discard one case and compensate.  That is, a variance of 1024 would
 * give us offsets in [0..1023].  Instead, we take offsets in [1..1023].
 * This is symmetric about the point 512, or statvar/2, and thus averages
 * to that value (assuming uniform random numbers).
 */
const int statvar = 1024;
int statmin;			/* minimum stat clock count in ticks */
int statcountperusec;		/* number of ticks per usec at current stathz */
int statprev;			/* last value of we set statclock to */

void footbridge_tc_init(void);

#if 0
static int clockmatch(device_t parent, cfdata_t cf, void *aux);
static void clockattach(device_t parent, device_t self, void *aux);

CFATTACH_DECL_NEW(footbridge_clock, sizeof(struct clock_softc),
    clockmatch, clockattach, NULL, NULL);

/*
 * int clockmatch(device_t parent, cfdata_t cf, void *aux);
 *
 * Just return ok for this if it is device 0
 */

static int
clockmatch(device_t parent, cfdata_t cf, void *aux)
{
	union footbridge_attach_args *fba = aux;

	if (strcmp(fba->fba_ca.ca_name, "clk") == 0)
		return 1;
	return 0;
}


/*
 * void clockattach(device_t parent, device_t self, void *aux)
 *
 */

static void
clockattach(device_t parent, device_t self, void *aux)
{
	struct clock_softc *sc = device_private(self);
	union footbridge_attach_args *fba = aux;

	sc->sc_dev = self;
	sc->sc_iot = fba->fba_ca.ca_iot;
	sc->sc_ioh = fba->fba_ca.ca_ioh;

	clock_sc = sc;

	/* Cannot do anything until cpu_initclocks() has been called */

	aprint_normal("\n");
}
#endif

/*
 * int clockhandler(struct clockframe *frame)
 *
 * Function called by timer 1 interrupts.
 * This just clears the interrupt condition and calls hardclock().
 */

int
clockhandler(void *aframe)
{
	struct clockframe *frame = aframe;
	bus_space_write_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    TIMER_1_CLEAR, 0);
	hardclock(frame);
	return 0;	/* Pass the interrupt on down the chain */
}

/*
 * int statclockhandler(struct clockframe *frame)
 *
 * Function called by timer 2 interrupts.
 * This just clears the interrupt condition and calls statclock().
 */

int
statclockhandler(void *aframe)
{
	struct clockframe *frame = aframe;
	int newint, r;
	int currentclock ;

	/* start the clock off again */
	bus_space_write_4(clock_sc->sc_iot, clock_sc->sc_ioh,
			TIMER_2_CLEAR, 0);

	do {
		r = random() & (statvar-1);
	} while (r == 0);
	newint = statmin + (r * statcountperusec);

	/* fetch the current count */
	currentclock = bus_space_read_4(clock_sc->sc_iot, clock_sc->sc_ioh,
		    TIMER_2_VALUE);

	/*
	 * work out how much time has run, add another usec for time spent
	 * here
	 */
	r = ((statprev - currentclock) + statcountperusec);

	if (r < newint) {
		newint -= r;
		r = 0;
	}
	else
		printf("statclockhandler: Statclock overrun\n");


	/*
	 * update the clock to the new counter, this reloads the existing
	 * timer
	 */
	bus_space_write_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    		TIMER_2_LOAD, newint);
	statprev = newint;
	statclock(frame);
	if (r)
		/*
		 * We've completely overrun the previous interval,
		 * make sure we report the correct number of ticks.
		 */
		statclock(frame);

	return 0;	/* Pass the interrupt on down the chain */
}

static int
load_timer(int base, int herz)
{
	unsigned int timer_count;
	int control;

	timer_count = dc21285_fclk / herz;
	if (timer_count > TIMER_MAX_VAL * 16) {
		control = TIMER_FCLK_256;
		timer_count >>= 8;
	} else if (timer_count > TIMER_MAX_VAL) {
		control = TIMER_FCLK_16;
		timer_count >>= 4;
	} else
		control = TIMER_FCLK;

	control |= (TIMER_ENABLE | TIMER_MODE_PERIODIC);
	bus_space_write_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    base + TIMER_LOAD, timer_count);
	bus_space_write_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    base + TIMER_CONTROL, control);
	bus_space_write_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    base + TIMER_CLEAR, 0);
	return timer_count;
}

/*
 * void setstatclockrate(int herz)
 *
 * Set the stat clock rate. The stat clock uses timer2
 */

void
setstatclockrate(int herz)
{
	int statint;
	int countpersecond;
	int statvarticks;

	/* statint == num in counter to drop by desired herz */
	statint = statprev = clock_sc->sc_statclock_count =
	    load_timer(TIMER_2_BASE, herz);

	/* Get the total ticks a second */
	countpersecond = statint * herz;

	/* now work out how many ticks per usec */
	statcountperusec = countpersecond / 1000000;

	/* calculate a variance range of statvar */
	statvarticks = statcountperusec * statvar;

	/* minimum is statint - 50% of variant */
	statmin = statint - (statvarticks / 2);
}

/*
 * void cpu_initclocks(void)
 *
 * Initialise the clocks.
 *
 * Timer 1 is used for the main system clock (hardclock)
 * Timer 2 is used for the statistics clock (statclock)
 */

void
cpu_initclocks(void)
{
	/* stathz and profhz should be set to something, we have the timer */
	if (stathz == 0)
		stathz = hz;

	if (profhz == 0)
		profhz = stathz * 5;

	/* Report the clock frequencies */
	aprint_debug("clock: hz=%d stathz = %d profhz = %d\n", hz, stathz, profhz);

	/* Setup timer 1 and claim interrupt */
	clock_sc->sc_clock_count = load_timer(TIMER_1_BASE, hz);

	/*
	 * Use ticks per 256us for accuracy since ticks per us is often
	 * fractional e.g. @ 66MHz
	 */
	clock_sc->sc_clock_ticks_per_256us =
	    ((((clock_sc->sc_clock_count * hz) / 1000) * 256) / 1000);
	clock_sc->sc_clockintr = footbridge_intr_claim(IRQ_TIMER_1, IPL_CLOCK,
	    "tmr1 hard clk", clockhandler, 0);

	if (clock_sc->sc_clockintr == NULL)
		panic("%s: Cannot install timer 1 interrupt handler",
		    device_xname(clock_sc->sc_dev));

	/* If stathz is non-zero then setup the stat clock */
	if (stathz) {
		/* Setup timer 2 and claim interrupt */
		setstatclockrate(stathz);
       		clock_sc->sc_statclockintr = footbridge_intr_claim(IRQ_TIMER_2, IPL_HIGH,
       		    "tmr2 stat clk", statclockhandler, 0);
		if (clock_sc->sc_statclockintr == NULL)
			panic("%s: Cannot install timer 2 interrupt handler",
			    device_xname(clock_sc->sc_dev));
	}

	footbridge_tc_init();
}

static uint32_t
fclk_get_count(struct timecounter *tc)
{
	return (TIMER_MAX_VAL -
	    bus_space_read_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    TIMER_3_VALUE));
}

void
footbridge_tc_init(void)
{
	static struct timecounter fb_tc = {
		.tc_get_timecount = fclk_get_count,
		.tc_counter_mask = TIMER_MAX_VAL,
		.tc_name = "dc21285_fclk",
		.tc_quality = 100
	};
	fb_tc.tc_frequency = dc21285_fclk;
	tc_init(&fb_tc);
}

/*
 * Use a timer to track microseconds, if the footbridge hasn't been setup we
 * rely on an estimated loop, however footbridge is attached very early on.
 */

static int delay_count_per_usec = 0;

void
calibrate_delay(void)
{
	/*
	 * For all current footbridge hardware, the fclk runs at a
	 * rate that is sufficiently slow enough that we don't need to
	 * use a prescaler.  A prescaler would be needed if the fclk
	 * could wrap within 2 hardclock periods (2 * HZ).  With
	 * normal values of HZ (100 and higher), this is unlikely to
	 * ever happen.
	 *
	 * We let TIMER 3 just run free, at the freqeuncy supplied by
	 * dc21285_fclk.
	 */
	bus_space_write_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    TIMER_3_BASE + TIMER_CONTROL, TIMER_ENABLE);
	delay_count_per_usec = dc21285_fclk / 1000000;
	if (dc21285_fclk % 1000000)
		delay_count_per_usec += 1;
}

void
delay(unsigned n)
{
	uint32_t cur, last, delta, usecs;

	if (n == 0)
		return;

	/*
	 * not calibrated the timer yet, so try to live with this horrible
	 * loop!
	 *
	 * Note: a much better solution might be to have the timers
	 * get get calibrated out of mach_init.  Of course, the
	 * clock_sc needs to be set up, so we can read/write the clock
	 * registers.
	 */
	if (!delay_count_per_usec)
	{
		/*
		 * the loop below has a core of 6 instructions
		 * StrongArms top out at 233Mhz, so one instruction takes
		 * 0.004 us, and 6 take 0.025 us, so we need to loop 40
		 * times to make one usec
		 */
		int delaycount = 40;
		volatile int i;

		while (n-- > 0) {
			for (i = delaycount; --i;);
		}
		return;
	}

	last = bus_space_read_4(clock_sc->sc_iot, clock_sc->sc_ioh,
	    TIMER_3_VALUE);
	delta = usecs = 0;

	while (n > usecs) {
		cur = bus_space_read_4(clock_sc->sc_iot, clock_sc->sc_ioh,
		    TIMER_3_VALUE);
		if (last < cur)
			/* timer has wrapped */
			delta += ((TIMER_MAX_VAL - cur) + last);
		else
			delta += (last - cur);

		last = cur;

		while (delta >= delay_count_per_usec) {
			delta -= delay_count_per_usec;
			usecs++;
		}
	}
}

/* End of footbridge_clock.c */