From 511107d85d6f2739a641076acfb5646ba2a19fc8 Mon Sep 17 00:00:00 2001
From: Anup Patel <anup@brainfault.org>
Date: Wed, 12 Dec 2018 06:12:31 -0800
Subject: [PATCH] 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>
---
arch/riscv/Kconfig | 8 ++++++++
arch/riscv/lib/Makefile | 1 +
arch/riscv/lib/rdtime.c | 38 ++++++++++++++++++++++++++++++++++++++
3 files changed, 47 insertions(+)
create mode 100644 arch/riscv/lib/rdtime.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index f513f52672..7dc6e3fad2 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -104,4 +104,12 @@ config SIFIVE_CLINT
The SiFive CLINT block holds memory-mapped control and status registers
associated with software and timer interrupts.
+config RISCV_RDTIME
+ bool
+ default y if RISCV_SMODE
+ help
+ The provides the riscv_get_time() API that is implemented using the
+ standard rdtime instruction. This is the case for S-mode U-Boot, and
+ is useful for processors that support rdtime in M-mode too.
+
endmenu
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index b13c87661e..edfa61690c 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -9,6 +9,7 @@
obj-$(CONFIG_CMD_BOOTM) += bootm.o
obj-$(CONFIG_CMD_GO) += boot.o
obj-y += cache.o
+obj-$(CONFIG_RISCV_RDTIME) += rdtime.o
obj-$(CONFIG_SIFIVE_CLINT) += sifive_clint.o
obj-y += interrupts.o
obj-y += reset.o
diff --git a/arch/riscv/lib/rdtime.c b/arch/riscv/lib/rdtime.c
new file mode 100644
index 0000000000..e128d7fce6
--- /dev/null
+++ b/arch/riscv/lib/rdtime.c
@@ -0,0 +1,38 @@
+// 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;
+}
--
2.39.5