u-boot/arch/riscv/lib/rdtime.c
Anup Patel 511107d85d riscv: Implement riscv_get_time() API using rdtime instruction
This adds an implementation of riscv_get_time() API that is using
rdtime instruction.

This is the case for S-mode U-Boot, and is useful for processors
that support rdtime in M-mode too.

Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
2018-12-18 09:56:27 +08:00

38 lines
676 B
C

// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2018, Anup Patel <anup@brainfault.org>
* Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
*
* The riscv_get_time() API implementation that is using the
* standard rdtime instruction.
*/
#include <common.h>
/* Implement the API required by RISC-V timer driver */
int riscv_get_time(u64 *time)
{
#ifdef CONFIG_64BIT
u64 n;
__asm__ __volatile__ (
"rdtime %0"
: "=r" (n));
*time = n;
#else
u32 lo, hi, tmp;
__asm__ __volatile__ (
"1:\n"
"rdtimeh %0\n"
"rdtime %1\n"
"rdtimeh %2\n"
"bne %0, %2, 1b"
: "=&r" (hi), "=&r" (lo), "=&r" (tmp));
*time = ((u64)hi << 32) | lo;
#endif
return 0;
}