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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2025 Google LLC
* Author: Vincent Donnefort <vdonnefort@google.com>
*/
#include <nvhe/clock.h>
#include <asm/arch_timer.h>
#include <asm/div64.h>
static struct clock_data {
struct {
u32 mult;
u32 shift;
u64 epoch_ns;
u64 epoch_cyc;
u64 cyc_overflow64;
} data[2];
u64 cur;
} trace_clock_data;
static u64 __clock_mult_uint128(u64 cyc, u32 mult, u32 shift)
{
__uint128_t ns = (__uint128_t)cyc * mult;
ns >>= shift;
return (u64)ns;
}
/* Does not guarantee no reader on the modified bank. */
void trace_clock_update(u32 mult, u32 shift, u64 epoch_ns, u64 epoch_cyc)
{
struct clock_data *clock = &trace_clock_data;
u64 bank = clock->cur ^ 1;
clock->data[bank].mult = mult;
clock->data[bank].shift = shift;
clock->data[bank].epoch_ns = epoch_ns;
clock->data[bank].epoch_cyc = epoch_cyc;
clock->data[bank].cyc_overflow64 = ULONG_MAX / mult;
smp_store_release(&clock->cur, bank);
}
/* Use untrusted host data */
u64 trace_clock(void)
{
struct clock_data *clock = &trace_clock_data;
u64 bank = smp_load_acquire(&clock->cur);
u64 cyc, ns;
cyc = __arch_counter_get_cntvct() - clock->data[bank].epoch_cyc;
if (likely(cyc < clock->data[bank].cyc_overflow64)) {
ns = cyc * clock->data[bank].mult;
ns >>= clock->data[bank].shift;
} else {
ns = __clock_mult_uint128(cyc, clock->data[bank].mult,
clock->data[bank].shift);
}
return (u64)ns + clock->data[bank].epoch_ns;
}
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