/*      $NetBSD: loongson_clock.c,v 1.3 2020/10/25 16:39:00 nia Exp $   */

/*
 * Copyright (c) 2011, 2016 Michael Lorenz
 * 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.
 *
 * 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 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: loongson_clock.c,v 1.3 2020/10/25 16:39:00 nia Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/device.h>
#include <sys/cpu.h>
#include <sys/timetc.h>
#include <sys/sysctl.h>

#include <mips/mips3_clock.h>
#include <mips/locore.h>
#include <mips/bonito/bonitoreg.h>
#include <mips/bonito/bonitovar.h>

#ifdef LOONGSON_CLOCK_DEBUG
#define DPRINTF aprint_error
#else
#define DPRINTF while (0) printf
#endif

static uint32_t sc_last;
static uint32_t sc_scale[8];
static uint32_t sc_count;       /* should probably be 64 bit */
static int sc_step = 7;
static int sc_step_wanted = 7;
static void *sc_shutdown_cookie;

/* 0, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8, 1 */
static int scale_m[] = {1, 1, 3, 1, 5, 3, 7, 1};
static int scale_d[] = {0, 4, 8, 2, 8, 4, 8, 1};
static int cycles[8];

#define scale(x, f) (x * scale_d[f] / scale_m[f])
#define rscale(x, f) (x * scale_m[f] / scale_d[f])

static void loongson_set_speed(int);
static int  loongson_cpuspeed_temp(SYSCTLFN_ARGS);
static int  loongson_cpuspeed_cur(SYSCTLFN_ARGS);
static int  loongson_cpuspeed_available(SYSCTLFN_ARGS);

static void loongson_clock_shutdown(void *);
static u_int get_loongson_timecount(struct timecounter *);
void        loongson_delay(int);
void        loongson_setstatclockrate(int);
void        loongson_initclocks(void);

static struct timecounter loongson_timecounter = {
        .tc_get_timecount = get_loongson_timecount,
        .tc_counter_mask = 0xffffffff,
        .tc_name = "loongson",
        .tc_quality = 100,
};

void
loongson_initclocks(void)
{
        const struct sysctlnode *sysctl_node, *me, *freq;
        int clk;

        /*
         * Establish a hook so on shutdown we can set the CPU clock back to
         * full speed. This is necessary because PMON doesn't change the 
         * clock scale register on a warm boot, the MIPS clock code gets
         * confused if we're too slow and the loongson-specific bits run
         * too late in the boot process
         */
        sc_shutdown_cookie = shutdownhook_establish(loongson_clock_shutdown, NULL);

        for (clk = 1; clk < 8; clk++) {
                sc_scale[clk] = rscale(curcpu()->ci_cpu_freq / 1000000, clk);
                cycles[clk] =
                    (rscale(curcpu()->ci_cpu_freq, clk) + hz / 2) / (2 * hz);
        }
#ifdef LOONGSON_CLOCK_DEBUG
        for (clk = 1; clk < 8; clk++) {
                aprint_normal("frequencies: %d/8: %d\n", clk + 1,
                    sc_scale[clk]);
        }
#endif

        /* now setup sysctl */
        if (sysctl_createv(NULL, 0, NULL, 
            &me, 
            CTLFLAG_READWRITE, CTLTYPE_NODE, "cpu", NULL, NULL,
            0, NULL, 0, CTL_MACHDEP, CTL_CREATE, CTL_EOL) != 0)
                aprint_error("couldn't create 'cpu' node\n");

        if (sysctl_createv(NULL, 0, NULL, 
            &freq, 
            CTLFLAG_READWRITE, CTLTYPE_NODE, "frequency", NULL, NULL, 0, NULL,
            0, CTL_MACHDEP, me->sysctl_num, CTL_CREATE, CTL_EOL) != 0)
                aprint_error("couldn't create 'frequency' node\n");

        if (sysctl_createv(NULL, 0, NULL, 
            &sysctl_node, 
            CTLFLAG_READWRITE | CTLFLAG_OWNDESC,
            CTLTYPE_INT, "target", "CPU speed", loongson_cpuspeed_temp, 
            0, NULL, 0, CTL_MACHDEP, me->sysctl_num, freq->sysctl_num, 
            CTL_CREATE, CTL_EOL) == 0) {
        } else
                aprint_error("couldn't create 'target' node\n");

        if (sysctl_createv(NULL, 0, NULL, 
            &sysctl_node, 
            CTLFLAG_READWRITE,
            CTLTYPE_INT, "current", NULL, loongson_cpuspeed_cur, 
            1, NULL, 0, CTL_MACHDEP, me->sysctl_num, freq->sysctl_num, 
            CTL_CREATE, CTL_EOL) == 0) {
        } else
                aprint_error("couldn't create 'current' node\n");

        if (sysctl_createv(NULL, 0, NULL, 
            &sysctl_node, 
            CTLFLAG_READWRITE,
            CTLTYPE_STRING, "available", NULL, loongson_cpuspeed_available, 
            2, NULL, 0, CTL_MACHDEP, me->sysctl_num, freq->sysctl_num, 
            CTL_CREATE, CTL_EOL) == 0) {
        } else
                aprint_error("couldn't create 'available' node\n");

        sc_count = 0;
        loongson_timecounter.tc_frequency = curcpu()->ci_cpu_freq / 2;
        curcpu()->ci_cctr_freq = loongson_timecounter.tc_frequency;

        sc_last = mips3_cp0_count_read();
        mips3_cp0_compare_write(sc_last + curcpu()->ci_cycles_per_hz);

        tc_init(&loongson_timecounter);

        /*
         * Now we can enable all interrupts including hardclock(9)
         * by CPU INT5.
         */
        spl0();
        printf("boom\n");
}

static void
loongson_clock_shutdown(void *cookie)
{

        /* just in case the interrupt handler runs again after this */
        sc_step_wanted = 7;
        /* set the clock to full speed */
        REGVAL(LS2F_CHIPCFG0) =
            (REGVAL(LS2F_CHIPCFG0) & ~LS2FCFG_FREQSCALE_MASK) | 7;
}

void
loongson_set_speed(int speed)
{

        if ((speed < 1) || (speed > 7))
                return;
        sc_step_wanted = speed;
        DPRINTF("%s: %d\n", __func__, speed);
}

/*
 * the clock interrupt handler
 * we don't have a CPU clock independent, high resolution counter so we're
 * stuck with a PWM that can't count and a CP0 counter that slows down or
 * speeds up with the actual CPU speed. In order to still get halfway
 * accurate time we do the following:
 * - only change CPU speed in the timer interrupt
 * - each timer interrupt we measure how many CP0 cycles passed since last
 *   time, adjust for CPU speed since we can be sure it didn't change, use
 *   that to update a separate counter
 * - when reading the time counter we take the number of CP0 ticks since 
 *   the last timer interrupt, scale it to CPU clock, return that plus the
 *   interrupt updated counter mentioned above to get something close to
 *   CP0 running at full speed 
 * - when changing CPU speed do it as close to taking the time from CP0 as
 *   possible to keep the period of time we spend with CP0 running at the
 *   wrong frequency as short as possible - hopefully short enough to stay
 *   insignificant compared to other noise since switching speeds isn't
 *   going to happen all that often
 */

void
mips3_clockintr(struct clockframe *cf)
{
        uint32_t now, diff, next, new_cnt;

        /*
         * this looks kinda funny but what we want here is this:
         * - reading the counter and changing the CPU clock should be as
         *   close together as possible in order to remain halfway accurate
         * - we need to use the previous sc_step in order to scale the
         *   interval passed since the last clock interrupt correctly, so
         *   we only change sc_step after doing that
         */
        if (sc_step_wanted != sc_step) {

                REGVAL(LS2F_CHIPCFG0) =
                    (REGVAL(LS2F_CHIPCFG0) & ~LS2FCFG_FREQSCALE_MASK) |
                     sc_step_wanted;
        }

        now = mips3_cp0_count_read();           
        diff = now - sc_last;
        sc_count += scale(diff, sc_step);
        sc_last = now;
        if (sc_step_wanted != sc_step) {
                sc_step = sc_step_wanted;
                curcpu()->ci_cycles_per_hz = cycles[sc_step];
        }
        next = now + curcpu()->ci_cycles_per_hz;
        curcpu()->ci_ev_count_compare.ev_count++;

        mips3_cp0_compare_write(next);

        /* Check for lost clock interrupts */
        new_cnt = mips3_cp0_count_read();

        /* 
         * Missed one or more clock interrupts, so let's start 
         * counting again from the current value.
         */
        if ((next - new_cnt) & 0x80000000) {

                next = new_cnt + curcpu()->ci_cycles_per_hz;
                mips3_cp0_compare_write(next);
                curcpu()->ci_ev_count_compare_missed.ev_count++;
        }
 
        hardclock(cf);
}

static u_int
get_loongson_timecount(struct timecounter *tc)
{
        uint32_t now, diff;

        now = mips3_cp0_count_read();
        diff = now - sc_last;
        return sc_count + scale(diff, sc_step);
}

static int
loongson_cpuspeed_temp(SYSCTLFN_ARGS)
{
        struct sysctlnode node = *rnode;
        int mhz, i;

        mhz = sc_scale[sc_step_wanted];

        node.sysctl_data = &mhz;
        if (sysctl_lookup(SYSCTLFN_CALL(&node)) == 0) {
                int new_reg;

                new_reg = *(int *)node.sysctl_data;
                i = 1;
                while ((i < 8) && (sc_scale[i] != new_reg))
                        i++;
                if (i > 7)
                        return EINVAL;
                loongson_set_speed(i);
                return 0;
        }
        return EINVAL;
}

static int
loongson_cpuspeed_cur(SYSCTLFN_ARGS)
{
        struct sysctlnode node = *rnode;
        int mhz;

        mhz = sc_scale[sc_step];
        node.sysctl_data = &mhz;
        return sysctl_lookup(SYSCTLFN_CALL(&node));
}

static int
loongson_cpuspeed_available(SYSCTLFN_ARGS)
{
        struct sysctlnode node = *rnode;
        char buf[128];

        snprintf(buf, 128, "%d %d %d %d %d %d %d", sc_scale[1],
            sc_scale[2], sc_scale[3], sc_scale[4],
            sc_scale[5], sc_scale[6], sc_scale[7]);
        node.sysctl_data = buf;
        return(sysctl_lookup(SYSCTLFN_CALL(&node)));
}

/*
 * Wait for at least "n" microseconds.
 */
void
loongson_delay(int n)
{
        u_long divisor_delay;
        uint32_t cur, last, delta, usecs;

        last = mips3_cp0_count_read();
        delta = usecs = 0;

        divisor_delay = rscale(curcpu()->ci_divisor_delay, sc_step);
        if (divisor_delay == 0) {
                /*
                 * Frequency values in curcpu() are not initialized.
                 * Assume faster frequency since longer delays are harmless.
                 * Note CPU_MIPS_DOUBLE_COUNT is ignored here.
                 */
#define FAST_FREQ       (300 * 1000 * 1000)     /* fast enough? */
                divisor_delay = FAST_FREQ / (1000 * 1000);
        }

        while (n > usecs) {
                cur = mips3_cp0_count_read();

                /*
                 * The MIPS3 CP0 counter always counts upto UINT32_MAX,
                 * so no need to check wrapped around case.
                 */
                delta += (cur - last);

                last = cur;

                while (delta >= divisor_delay) {
                        /*
                         * delta is not so larger than divisor_delay here,
                         * and using DIV/DIVU ops could be much slower.
                         * (though longer delay may be harmless)
                         */
                        usecs++;
                        delta -= divisor_delay;
                }
        }
}

SYSCTL_SETUP(sysctl_ams_setup, "sysctl obio subtree setup")
{

        sysctl_createv(NULL, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "machdep", NULL,
                       NULL, 0, NULL, 0,
                       CTL_MACHDEP, CTL_EOL);
}

/*
 * We assume newhz is either stathz or profhz, and that neither will
 * change after being set up above.  Could recalculate intervals here
 * but that would be a drag.
 */
void
loongson_setstatclockrate(int newhz)
{

        /* nothing we can do */
}

__weak_alias(setstatclockrate, loongson_setstatclockrate);
__weak_alias(cpu_initclocks, loongson_initclocks);
__weak_alias(delay, loongson_delay);