/*
 * Userspace implementations of gettimeofday() and friends.
 *
 * Copyright (C) 2012 ARM Limited
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 * Author: Will Deacon <will.deacon@arm.com>
 */

#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/unistd.h>

#define NSEC_PER_SEC_LO16       0xca00
#define NSEC_PER_SEC_HI16       0x3b9a

vdso_data       .req    x6
seqcnt          .req    w7
w_tmp           .req    w8
x_tmp           .req    x8

/*
 * Conventions for macro arguments:
 * - An argument is write-only if its name starts with "res".
 * - All other arguments are read-only, unless otherwise specified.
 */

        .macro  seqcnt_acquire
9999:   ldr     seqcnt, [vdso_data, #VDSO_TB_SEQ_COUNT]
        tbnz    seqcnt, #0, 9999b
        dmb     ishld
        .endm

        .macro  seqcnt_check fail
        dmb     ishld
        ldr     w_tmp, [vdso_data, #VDSO_TB_SEQ_COUNT]
        cmp     w_tmp, seqcnt
        b.ne    \fail
        .endm

        .macro  syscall_check fail
        ldr     w_tmp, [vdso_data, #VDSO_USE_SYSCALL]
        cbnz    w_tmp, \fail
        .endm

        .macro get_nsec_per_sec res
        mov     \res, #NSEC_PER_SEC_LO16
        movk    \res, #NSEC_PER_SEC_HI16, lsl #16
        .endm

        /*
         * Returns the clock delta, in nanoseconds left-shifted by the clock
         * shift.
         */
        .macro  get_clock_shifted_nsec res, cycle_last, mult
        /* Read the virtual counter. */
        isb
        mrs     x_tmp, cntvct_el0
        /* Calculate cycle delta and convert to ns. */
        sub     \res, x_tmp, \cycle_last
        /* We can only guarantee 56 bits of precision. */
        movn    x_tmp, #0xff00, lsl #48
        and     \res, x_tmp, \res
        mul     \res, \res, \mult
        .endm

        /*
         * Returns in res_{sec,nsec} the REALTIME timespec, based on the
         * "wall time" (xtime) and the clock_mono delta.
         */
        .macro  get_ts_realtime res_sec, res_nsec, \
                        clock_nsec, xtime_sec, xtime_nsec, nsec_to_sec
        add     \res_nsec, \clock_nsec, \xtime_nsec
        udiv    x_tmp, \res_nsec, \nsec_to_sec
        add     \res_sec, \xtime_sec, x_tmp
        msub    \res_nsec, x_tmp, \nsec_to_sec, \res_nsec
        .endm

        /*
         * Returns in res_{sec,nsec} the timespec based on the clock_raw delta,
         * used for CLOCK_MONOTONIC_RAW.
         */
        .macro  get_ts_clock_raw res_sec, res_nsec, clock_nsec, nsec_to_sec
        udiv    \res_sec, \clock_nsec, \nsec_to_sec
        msub    \res_nsec, \res_sec, \nsec_to_sec, \clock_nsec
        .endm

        /* sec and nsec are modified in place. */
        .macro add_ts sec, nsec, ts_sec, ts_nsec, nsec_to_sec
        /* Add timespec. */
        add     \sec, \sec, \ts_sec
        add     \nsec, \nsec, \ts_nsec

        /* Normalise the new timespec. */
        cmp     \nsec, \nsec_to_sec
        b.lt    9999f
        sub     \nsec, \nsec, \nsec_to_sec
        add     \sec, \sec, #1
9999:
        cmp     \nsec, #0
        b.ge    9998f
        add     \nsec, \nsec, \nsec_to_sec
        sub     \sec, \sec, #1
9998:
        .endm

        .macro clock_gettime_return, shift=0
        .if \shift == 1
        lsr     x11, x11, x12
        .endif
        stp     x10, x11, [x1, #TSPEC_TV_SEC]
        mov     x0, xzr
        ret
        .endm

        .macro jump_slot jumptable, index, label
        .if (. - \jumptable) != 4 * (\index)
        .error "Jump slot index mismatch"
        .endif
        b       \label
        .endm

        .text

/* int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz); */
ENTRY(__kernel_gettimeofday)
        .cfi_startproc
        adr     vdso_data, _vdso_data
        /* If tv is NULL, skip to the timezone code. */
        cbz     x0, 2f

        /* Compute the time of day. */
1:      seqcnt_acquire
        syscall_check fail=4f
        ldr     x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
        /* w11 = cs_mono_mult, w12 = cs_shift */
        ldp     w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
        ldp     x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
        seqcnt_check fail=1b

        get_nsec_per_sec res=x9
        lsl     x9, x9, x12

        get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
        get_ts_realtime res_sec=x10, res_nsec=x11, \
                clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9

        /* Convert ns to us. */
        mov     x13, #1000
        lsl     x13, x13, x12
        udiv    x11, x11, x13
        stp     x10, x11, [x0, #TVAL_TV_SEC]
2:
        /* If tz is NULL, return 0. */
        cbz     x1, 3f
        ldp     w4, w5, [vdso_data, #VDSO_TZ_MINWEST]
        stp     w4, w5, [x1, #TZ_MINWEST]
3:
        mov     x0, xzr
        ret
4:
        /* Syscall fallback. */
        mov     x8, #__NR_gettimeofday
        svc     #0
        ret
        .cfi_endproc
ENDPROC(__kernel_gettimeofday)

#define JUMPSLOT_MAX CLOCK_MONOTONIC_COARSE

/* int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp); */
ENTRY(__kernel_clock_gettime)
        .cfi_startproc
        cmp     w0, #JUMPSLOT_MAX
        b.hi    syscall
        adr     vdso_data, _vdso_data
        adr     x_tmp, jumptable
        add     x_tmp, x_tmp, w0, uxtw #2
        br      x_tmp

        ALIGN
jumptable:
        jump_slot jumptable, CLOCK_REALTIME, realtime
        jump_slot jumptable, CLOCK_MONOTONIC, monotonic
        b       syscall
        b       syscall
        jump_slot jumptable, CLOCK_MONOTONIC_RAW, monotonic_raw
        jump_slot jumptable, CLOCK_REALTIME_COARSE, realtime_coarse
        jump_slot jumptable, CLOCK_MONOTONIC_COARSE, monotonic_coarse

        .if (. - jumptable) != 4 * (JUMPSLOT_MAX + 1)
        .error  "Wrong jumptable size"
        .endif

        ALIGN
realtime:
        seqcnt_acquire
        syscall_check fail=syscall
        ldr     x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
        /* w11 = cs_mono_mult, w12 = cs_shift */
        ldp     w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
        ldp     x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
        seqcnt_check fail=realtime

        /* All computations are done with left-shifted nsecs. */
        get_nsec_per_sec res=x9
        lsl     x9, x9, x12

        get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
        get_ts_realtime res_sec=x10, res_nsec=x11, \
                clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9
        clock_gettime_return, shift=1

        ALIGN
monotonic:
        seqcnt_acquire
        syscall_check fail=syscall
        ldr     x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
        /* w11 = cs_mono_mult, w12 = cs_shift */
        ldp     w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
        ldp     x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
        ldp     x3, x4, [vdso_data, #VDSO_WTM_CLK_SEC]
        seqcnt_check fail=monotonic

        /* All computations are done with left-shifted nsecs. */
        lsl     x4, x4, x12
        get_nsec_per_sec res=x9
        lsl     x9, x9, x12

        get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
        get_ts_realtime res_sec=x10, res_nsec=x11, \
                clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9

        add_ts sec=x10, nsec=x11, ts_sec=x3, ts_nsec=x4, nsec_to_sec=x9
        clock_gettime_return, shift=1

        ALIGN
monotonic_raw:
        seqcnt_acquire
        syscall_check fail=syscall
        ldr     x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
        /* w11 = cs_raw_mult, w12 = cs_shift */
        ldp     w12, w11, [vdso_data, #VDSO_CS_SHIFT]
        ldp     x13, x14, [vdso_data, #VDSO_RAW_TIME_SEC]
        seqcnt_check fail=monotonic_raw

        /* All computations are done with left-shifted nsecs. */
        get_nsec_per_sec res=x9
        lsl     x9, x9, x12

        get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
        get_ts_clock_raw res_sec=x10, res_nsec=x11, \
                clock_nsec=x15, nsec_to_sec=x9

        add_ts sec=x10, nsec=x11, ts_sec=x13, ts_nsec=x14, nsec_to_sec=x9
        clock_gettime_return, shift=1

        ALIGN
realtime_coarse:
        seqcnt_acquire
        ldp     x10, x11, [vdso_data, #VDSO_XTIME_CRS_SEC]
        seqcnt_check fail=realtime_coarse
        clock_gettime_return

        ALIGN
monotonic_coarse:
        seqcnt_acquire
        ldp     x10, x11, [vdso_data, #VDSO_XTIME_CRS_SEC]
        ldp     x13, x14, [vdso_data, #VDSO_WTM_CLK_SEC]
        seqcnt_check fail=monotonic_coarse

        /* Computations are done in (non-shifted) nsecs. */
        get_nsec_per_sec res=x9
        add_ts sec=x10, nsec=x11, ts_sec=x13, ts_nsec=x14, nsec_to_sec=x9
        clock_gettime_return

        ALIGN
syscall: /* Syscall fallback. */
        mov     x8, #__NR_clock_gettime
        svc     #0
        ret
        .cfi_endproc
ENDPROC(__kernel_clock_gettime)

/* int __kernel_clock_getres(clockid_t clock_id, struct timespec *res); */
ENTRY(__kernel_clock_getres)
        .cfi_startproc
        cmp     w0, #CLOCK_REALTIME
        ccmp    w0, #CLOCK_MONOTONIC, #0x4, ne
        ccmp    w0, #CLOCK_MONOTONIC_RAW, #0x4, ne
        b.ne    1f

        ldr     x2, 5f
        b       2f
1:
        cmp     w0, #CLOCK_REALTIME_COARSE
        ccmp    w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne
        b.ne    4f
        ldr     x2, 6f
2:
        cbz     w1, 3f
        stp     xzr, x2, [x1]

3:      /* res == NULL. */
        mov     w0, wzr
        ret

4:      /* Syscall fallback. */
        mov     x8, #__NR_clock_getres
        svc     #0
        ret
5:
        .quad   CLOCK_REALTIME_RES
6:
        .quad   CLOCK_COARSE_RES
        .cfi_endproc
ENDPROC(__kernel_clock_getres)