/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */

/*
 * Copyright 2022 Oxide Computer Company
 */

#include "payload_common.h"
#include "payload_utils.h"
#include "test_defs.h"

#define LAPIC_OFF_SVR   0xf0
#define LAPIC_OFF_LVT_TIMER     0x320
#define LAPIC_OFF_TIMER_ICR     0x380
#define LAPIC_OFF_TIMER_CCR     0x390
#define LAPIC_OFF_TIMER_DCR     0x3e0

#define LAPIC_LVT_MASKED        (1 << 16)
#define LAPIC_LVT_PERIODIC      (1 << 17)


#define LAPIC_SVR_ENABLE        0x100

static void
write_vlapic(uint_t reg, uint32_t value)
{
        volatile uint32_t *ptr = (uint32_t *)(MMIO_LAPIC_BASE + reg);
        *ptr = value;
}

static uint32_t
read_vlapic(uint_t reg)
{
        volatile uint32_t *ptr = (uint32_t *)(MMIO_LAPIC_BASE + reg);
        return (*ptr);
}

static uint32_t
divisor_to_dcr(uint32_t inp)
{
        switch (inp) {
        case 1:
                return (0xb);
        case 2:
                return (0x0);
        case 4:
                return (0x1);
        case 8:
                return (0x2);
        case 16:
                return (0x3);
        case 32:
                return (0x8);
        case 64:
                return (0x9);
        case 128:
                return (0xa);
        default:
                /* fail immediate if divisor is out of range */
                outl(IOP_TEST_VALUE, 1);
                return (0xff);
        }
}


void
start(void)
{
        write_vlapic(LAPIC_OFF_SVR, LAPIC_SVR_ENABLE);

        /*
         * Configure the LAPIC timer for periodic operation, but leave the
         * interrupt itself masked.
         */
        write_vlapic(LAPIC_OFF_LVT_TIMER,
            LAPIC_LVT_MASKED | LAPIC_LVT_PERIODIC);

        /* loop for as long as the host wants */
        for (;;) {
                const uint16_t divisor = inw(IOP_TEST_PARAM0);
                const uint16_t loop_count = inw(IOP_TEST_PARAM1);

                write_vlapic(LAPIC_OFF_TIMER_DCR, divisor_to_dcr(divisor));
                write_vlapic(LAPIC_OFF_TIMER_ICR, LAPIC_TARGET_TICKS);

                uint32_t start, end, count = 0;
                start = read_vlapic(LAPIC_OFF_TIMER_CCR);
                outl(IOP_TEST_VALUE, start);

                uint32_t prev = start;
                do {
                        end = read_vlapic(LAPIC_OFF_TIMER_CCR);

                        /* timer period rolled over */
                        if (end > prev) {
                                count++;
                        }
                        prev = end;
                } while (count < loop_count);
                outl(IOP_TEST_VALUE, end);
        }
}