/*
 *
 * Copyright (C) 2001 MontaVista Software, ppopov@mvista.com
 * Copied and modified Carsten Langgaard's time.c
 *
 * Carsten Langgaard, carstenl@mips.com
 * Copyright (C) 1999,2000 MIPS Technologies, Inc.  All rights reserved.
 *
 * ########################################################################
 *
 *  This program is free software; you can distribute 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 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.
 *
 * ########################################################################
 *
 * Setting up the clock on the MIPS boards.
 *
 * Update.  Always configure the kernel with CONFIG_NEW_TIME_C.  This
 * will use the user interface gettimeofday() functions from the
 * arch/mips/kernel/time.c, and we provide the clock interrupt processing
 * and the timer offset compute functions.  If CONFIG_PM is selected,
 * we also ensure the 32KHz timer is available.   -- Dan
 */

#include <linux/types.h>
#include <linux/config.h>
#include <linux/init.h>
#include <linux/kernel_stat.h>
#include <linux/sched.h>
#include <linux/spinlock.h>

#include <asm/compiler.h>
#include <asm/mipsregs.h>
#include <asm/ptrace.h>
#include <asm/time.h>
#include <asm/hardirq.h>
#include <asm/div64.h>
#include <asm/au1000.h>

#include <linux/mc146818rtc.h>
#include <linux/timex.h>

extern void startup_match20_interrupt(void);
extern void do_softirq(void);
extern volatile unsigned long wall_jiffies;
unsigned long missed_heart_beats = 0;

static unsigned long r4k_offset; /* Amount to increment compare reg each time */
static unsigned long r4k_cur;    /* What counter should be at next timer irq */
extern rwlock_t xtime_lock;
int     no_au1xxx_32khz;
void    (*au1k_wait_ptr)(void);

/* Cycle counter value at the previous timer interrupt.. */
static unsigned int timerhi = 0, timerlo = 0;

#ifdef CONFIG_PM
#define MATCH20_INC 328
extern void startup_match20_interrupt(void);
static unsigned long last_pc0, last_match20;
#endif

static spinlock_t time_lock = SPIN_LOCK_UNLOCKED;

static inline void ack_r4ktimer(unsigned long newval)
{
        write_c0_compare(newval);
}

/*
 * There are a lot of conceptually broken versions of the MIPS timer interrupt
 * handler floating around.  This one is rather different, but the algorithm
 * is provably more robust.
 */
unsigned long wtimer;
void mips_timer_interrupt(struct pt_regs *regs)
{
        int irq = 63;
        unsigned long count;
        int cpu = smp_processor_id();

        irq_enter(cpu, irq);
        kstat.irqs[cpu][irq]++;

        if (r4k_offset == 0)
                goto null;

        do {
                count = read_c0_count();
                timerhi += (count < timerlo);   /* Wrap around */
                timerlo = count;

                kstat.irqs[0][irq]++;
                do_timer(regs);
                r4k_cur += r4k_offset;
                ack_r4ktimer(r4k_cur);

        } while (((unsigned long)read_c0_count()
                 - r4k_cur) < 0x7fffffff);

        irq_exit(cpu, irq);

        if (softirq_pending(cpu))
                do_softirq();
        return;

null:
        ack_r4ktimer(0);
}

#ifdef CONFIG_PM
void counter0_irq(int irq, void *dev_id, struct pt_regs *regs)
{
        unsigned long pc0;
        int time_elapsed;
        static int jiffie_drift = 0;

        kstat.irqs[0][irq]++;
        if (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_M20) {
                /* should never happen! */
                printk(KERN_WARNING "counter 0 w status eror\n");
                return;
        }

        pc0 = au_readl(SYS_TOYREAD);
        if (pc0 < last_match20) {
                /* counter overflowed */
                time_elapsed = (0xffffffff - last_match20) + pc0;
        }
        else {
                time_elapsed = pc0 - last_match20;
        }

        while (time_elapsed > 0) {
                do_timer(regs);
                time_elapsed -= MATCH20_INC;
                last_match20 += MATCH20_INC;
                jiffie_drift++;
        }

        last_pc0 = pc0;
        au_writel(last_match20 + MATCH20_INC, SYS_TOYMATCH2);
        au_sync();

        /* our counter ticks at 10.009765625 ms/tick, we we're running
         * almost 10uS too slow per tick.
         */

        if (jiffie_drift >= 999) {
                jiffie_drift -= 999;
                do_timer(regs); /* increment jiffies by one */
        }
}

/* When we wakeup from sleep, we have to "catch up" on all of the
 * timer ticks we have missed.
 */
void
wakeup_counter0_adjust(void)
{
        unsigned long pc0;
        int time_elapsed;

        pc0 = au_readl(SYS_TOYREAD);
        if (pc0 < last_match20) {
                /* counter overflowed */
                time_elapsed = (0xffffffff - last_match20) + pc0;
        }
        else {
                time_elapsed = pc0 - last_match20;
        }

        while (time_elapsed > 0) {
                time_elapsed -= MATCH20_INC;
                last_match20 += MATCH20_INC;
        }

        last_pc0 = pc0;
        au_writel(last_match20 + MATCH20_INC, SYS_TOYMATCH2);
        au_sync();

}

/* This is just for debugging to set the timer for a sleep delay.
*/
void
wakeup_counter0_set(int ticks)
{
        unsigned long pc0;

        pc0 = au_readl(SYS_TOYREAD);
        last_pc0 = pc0;
        au_writel(last_match20 + (MATCH20_INC * ticks), SYS_TOYMATCH2);
        au_sync();
}
#endif

/* I haven't found anyone that doesn't use a 12 MHz source clock,
 * but just in case.....
 */
#ifdef CONFIG_AU1000_SRC_CLK
#define AU1000_SRC_CLK  CONFIG_AU1000_SRC_CLK
#else
#define AU1000_SRC_CLK  12000000
#endif

/*
 * We read the real processor speed from the PLL.  This is important
 * because it is more accurate than computing it from the 32KHz
 * counter, if it exists.  If we don't have an accurate processor
 * speed, all of the peripherals that derive their clocks based on
 * this advertised speed will introduce error and sometimes not work
 * properly.  This function is futher convoluted to still allow configurations
 * to do that in case they have really, really old silicon with a
 * write-only PLL register, that we need the 32KHz when power management
 * "wait" is enabled, and we need to detect if the 32KHz isn't present
 * but requested......got it? :-)               -- Dan
 */
unsigned long cal_r4koff(void)
{
        unsigned long count;
        unsigned long cpu_speed;
        unsigned long flags;
        unsigned long counter;

        spin_lock_irqsave(&time_lock, flags);

        /* Power management cares if we don't have a 32KHz counter.
        */
        no_au1xxx_32khz = 0;
        counter = au_readl(SYS_COUNTER_CNTRL);
        if (counter & SYS_CNTRL_E0) {
                int trim_divide = 16;

                au_writel(counter | SYS_CNTRL_EN1, SYS_COUNTER_CNTRL);

                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_T1S);
                /* RTC now ticks at 32.768/16 kHz */
                au_writel(trim_divide-1, SYS_RTCTRIM);
                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_T1S);

                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C1S);
                au_writel (0, SYS_TOYWRITE);
                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C1S);

#if defined(CONFIG_AU1000_USE32K)
                {
                        unsigned long start, end;

                        start = au_readl(SYS_RTCREAD);
                        start += 2;
                        /* wait for the beginning of a new tick
                        */
                        while (au_readl(SYS_RTCREAD) < start);

                        /* Start r4k counter.
                        */
                        write_c0_count(0);

                        /* Wait 0.5 seconds.
                        */
                        end = start + (32768 / trim_divide)/2;

                        while (end > au_readl(SYS_RTCREAD));

                        count = read_c0_count();
                        cpu_speed = count * 2;
                }
#else
                cpu_speed = (au_readl(SYS_CPUPLL) & 0x0000003f) * 
                        AU1000_SRC_CLK;
                count = cpu_speed / 2;
#endif
        }
        else {
                /* The 32KHz oscillator isn't running, so assume there
                 * isn't one and grab the processor speed from the PLL.
                 * NOTE: some old silicon doesn't allow reading the PLL.
                 */
                cpu_speed = (au_readl(SYS_CPUPLL) & 0x0000003f) * AU1000_SRC_CLK;
                count = cpu_speed / 2;
                no_au1xxx_32khz = 1;
        }
        mips_hpt_frequency = count;
        // Equation: Baudrate = CPU / (SD * 2 * CLKDIV * 16)
        set_au1x00_uart_baud_base(cpu_speed / (2 * ((int)(au_readl(SYS_POWERCTRL)&0x03) + 2) * 16));
        spin_unlock_irqrestore(&time_lock, flags);
        return (cpu_speed / HZ);
}

/* This is for machines which generate the exact clock. */
#define USECS_PER_JIFFY (1000000/HZ)
#define USECS_PER_JIFFY_FRAC (0x100000000*1000000/HZ&0xffffffff)


static unsigned long
div64_32(unsigned long v1, unsigned long v2, unsigned long v3)
{
        unsigned long r0;
        do_div64_32(r0, v1, v2, v3);
        return r0;
}

static unsigned long do_fast_cp0_gettimeoffset(void)
{
        u32 count;
        unsigned long res, tmp;
        unsigned long r0;

        /* Last jiffy when do_fast_gettimeoffset() was called. */
        static unsigned long last_jiffies=0;
        unsigned long quotient;

        /*
         * Cached "1/(clocks per usec)*2^32" value.
         * It has to be recalculated once each jiffy.
         */
        static unsigned long cached_quotient=0;

        tmp = jiffies;

        quotient = cached_quotient;

        if (tmp && last_jiffies != tmp) {
                last_jiffies = tmp;
                if (last_jiffies != 0) {
                        r0 = div64_32(timerhi, timerlo, tmp);
                        quotient = div64_32(USECS_PER_JIFFY, USECS_PER_JIFFY_FRAC, r0);
                        cached_quotient = quotient;
                }
        }

        /* Get last timer tick in absolute kernel time */
        count = read_c0_count();

        /* .. relative to previous jiffy (32 bits is enough) */
        count -= timerlo;

        __asm__("multu\t%1,%2\n\t"
                "mfhi\t%0"
                : "=r" (res)
                : "r" (count), "r" (quotient)
                : "hi", "lo", GCC_REG_ACCUM);

        /*
         * Due to possible jiffies inconsistencies, we need to check 
         * the result so that we'll get a timer that is monotonic.
         */
        if (res >= USECS_PER_JIFFY)
                res = USECS_PER_JIFFY-1;

        return res;
}

#ifdef CONFIG_PM
static unsigned long do_fast_pm_gettimeoffset(void)
{
        unsigned long pc0;
        unsigned long offset;

        pc0 = au_readl(SYS_TOYREAD);
        au_sync();
        offset = pc0 - last_pc0;
        if (offset > 2*MATCH20_INC) {
                printk("huge offset %x, last_pc0 %x last_match20 %x pc0 %x\n", 
                                (unsigned)offset, (unsigned)last_pc0, 
                                (unsigned)last_match20, (unsigned)pc0);
        }
        offset = (unsigned long)((offset * 305) / 10);
        return offset;
}
#endif

void __init au1xxx_timer_setup(void)
{
        unsigned int est_freq;
        extern unsigned long (*do_gettimeoffset)(void);
        extern void au1k_wait(void);

        printk("calculating r4koff... ");
        r4k_offset = cal_r4koff();
        printk("%08lx(%d)\n", r4k_offset, (int) r4k_offset);

        //est_freq = 2*r4k_offset*HZ;   
        est_freq = r4k_offset*HZ;       
        est_freq += 5000;    /* round */
        est_freq -= est_freq%10000;
        printk("CPU frequency %d.%02d MHz\n", est_freq/1000000, 
               (est_freq%1000000)*100/1000000);
        set_au1x00_speed(est_freq);
        set_au1x00_lcd_clock(); // program the LCD clock

        r4k_cur = (read_c0_count() + r4k_offset);
        write_c0_compare(r4k_cur);

        /* no RTC on the pb1000 */
        xtime.tv_sec = 0;
        xtime.tv_usec = 0;

#ifdef CONFIG_PM
        /*
         * setup counter 0, since it keeps ticking after a
         * 'wait' instruction has been executed. The CP0 timer and
         * counter 1 do NOT continue running after 'wait'
         *
         * It's too early to call request_irq() here, so we handle
         * counter 0 interrupt as a special irq and it doesn't show
         * up under /proc/interrupts.
         *
         * Check to ensure we really have a 32KHz oscillator before
         * we do this.
         */
        if (no_au1xxx_32khz) {
                unsigned int c0_status;

                printk("WARNING: no 32KHz clock found.\n");
                do_gettimeoffset = do_fast_cp0_gettimeoffset;

                /* Ensure we get CPO_COUNTER interrupts.
                */
                c0_status = read_c0_status();
                c0_status |= IE_IRQ5;
                write_c0_status(c0_status);
        }
        else {
                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C0S);
                au_writel(0, SYS_TOYWRITE);
                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C0S);

                au_writel(au_readl(SYS_WAKEMSK) | (1<<8), SYS_WAKEMSK);
                au_writel(~0, SYS_WAKESRC);
                au_sync();
                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_M20);

                /* setup match20 to interrupt once every 10ms */
                last_pc0 = last_match20 = au_readl(SYS_TOYREAD);
                au_writel(last_match20 + MATCH20_INC, SYS_TOYMATCH2);
                au_sync();
                while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_M20);
                startup_match20_interrupt();

                do_gettimeoffset = do_fast_pm_gettimeoffset;

                /* We can use the real 'wait' instruction.
                */
                au1k_wait_ptr = au1k_wait;
        }

#else
        /* We have to do this here instead of in timer_init because
         * the generic code in arch/mips/kernel/time.c will write
         * over our function pointer.
         */
        do_gettimeoffset = do_fast_cp0_gettimeoffset;
#endif
}

void __init au1xxx_time_init(void)
{
}