/*
 * Copyright (C) 2009 Broadcom Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <linux/init.h>
#include <linux/clocksource.h>
#include <linux/spinlock.h>

#include <asm/time.h>
#include <asm/brcmstb/brcmstb.h>

/* MIPS clock measured at boot time.  Value is not changed by PM. */
unsigned long brcm_cpu_khz;

/* Sampling period for MIPS calibration.  50 = 1/50 of a second. */
#define SAMPLE_PERIOD		50

/***********************************************************************
 * UPG clocksource
 ***********************************************************************/

static cycle_t upg_cs_read(struct clocksource *cs)
{
	return BDEV_RD_F(TIMER_TIMER3_STAT, COUNTER_VAL);
}

static struct clocksource clocksource_upg = {
	.name		= "upg",
	.read		= upg_cs_read,
	.mask		= CLOCKSOURCE_MASK(30),
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

static inline void __init init_upg_clocksource(void)
{
	BDEV_WR_RB(BCHP_TIMER_TIMER3_CTRL, 0);
	BDEV_WR_F_RB(TIMER_TIMER_IS, TMR3TO, 1);
	BDEV_WR_RB(BCHP_TIMER_TIMER3_CTRL, 0xbfffffff);

	clocksource_upg.rating = 250;
	clocksource_register_hz(&clocksource_upg, UPGTMR_FREQ);
}

#ifdef CONFIG_BRCM_HAS_WKTMR

/***********************************************************************
 * WKTMR clocksource
 ***********************************************************************/

static DEFINE_SPINLOCK(wktmr_lock);

static cycle_t wktmr_cs_read(struct clocksource *cs)
{
	struct wktmr_time t;
	unsigned long flags;

	spin_lock_irqsave(&wktmr_lock, flags);
	wktmr_read(&t);
	spin_unlock_irqrestore(&wktmr_lock, flags);

	return (t.sec * (cycle_t)WKTMR_FREQ) + t.pre;
}

static struct clocksource clocksource_wktmr = {
	.name		= "wktmr",
	.read		= wktmr_cs_read,
	.mask		= CLOCKSOURCE_MASK(64),
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

static inline void __init init_wktmr_clocksource(void)
{
	clocksource_wktmr.rating = 250;
	clocksource_register_hz(&clocksource_wktmr, WKTMR_FREQ);
}

/***********************************************************************
 * WKTMR utility functions (boot time only)
 ***********************************************************************/

void wktmr_read(struct wktmr_time *t)
{
	uint32_t tmp;

	do {
		t->sec = BDEV_RD(BCHP_WKTMR_COUNTER);
		tmp = BDEV_RD(BCHP_WKTMR_PRESCALER_VAL);
	} while (tmp >= WKTMR_FREQ);

	t->pre = WKTMR_FREQ - tmp;
}

unsigned long wktmr_elapsed(struct wktmr_time *t)
{
	struct wktmr_time now;

	wktmr_read(&now);
	now.sec -= t->sec;
	if (now.pre > t->pre) {
		now.pre -= t->pre;
	} else {
		now.pre = WKTMR_FREQ + now.pre - t->pre;
		now.sec--;
	}
	return (now.sec * WKTMR_FREQ) + now.pre;
}

/*
 * MIPS frequency calibration (WKTMR)
 */

static __init unsigned long brcm_mips_freq(void)
{
	struct wktmr_time start;

	wktmr_read(&start);
	write_c0_count(0);

	while (wktmr_elapsed(&start) < (WKTMR_FREQ / SAMPLE_PERIOD))
		;

	return read_c0_count() * SAMPLE_PERIOD;
}

#else /* CONFIG_BRCM_HAS_WKTMR */

/*
 * MIPS frequency calibration (UPG TIMER3)
 */

static __init unsigned long brcm_mips_freq(void)
{
	unsigned long ret;

	/* reset countdown timer */
	BDEV_WR_RB(BCHP_TIMER_TIMER3_CTRL, 0);
	BDEV_WR_F_RB(TIMER_TIMER_IS, TMR3TO, 1);

	/* set up for countdown */
	BDEV_WR(BCHP_TIMER_TIMER0_CTRL, 0xc0000000 |
		(UPGTMR_FREQ / SAMPLE_PERIOD));
	write_c0_count(0);

	while ((BDEV_RD(BCHP_TIMER_TIMER_IS) & 1) == 0)
		;

	ret = read_c0_count();
	BDEV_WR(BCHP_TIMER_TIMER0_CTRL, 0);

	return ret * SAMPLE_PERIOD;
}

#endif /* CONFIG_BRCM_HAS_WKTMR */

/***********************************************************************
 * Timer setup
 ***********************************************************************/

void __init plat_time_init(void)
{
	unsigned int khz;

	printk(KERN_DEBUG "Measuring MIPS counter frequency...\n");
	mips_hpt_frequency = brcm_mips_freq();
	khz = mips_hpt_frequency / 1000;
#ifdef CONFIG_BMIPS5000
	brcm_cpu_khz = mips_hpt_frequency * 8 / 1000;
#else
	brcm_cpu_khz = mips_hpt_frequency * 2 / 1000;
#endif

	printk(KERN_INFO "Detected MIPS clock frequency: %lu MHz "
		"(%u.%03u MHz counter)\n", brcm_cpu_khz / 1000,
		khz / 1000, khz % 1000);

#ifdef CONFIG_CSRC_WKTMR
	init_wktmr_clocksource();
#endif
#ifdef CONFIG_CSRC_UPG
	init_upg_clocksource();
#endif
}