arch/riscv: provide a monotonic timer

The RISC-V Privileged Architecture specification defines the Machine
Time Registers (mtime and mtimecmp) in section 3.1.15.

Makes it possible to use the generic udelay.
The timer is enabled using RISCV_USE_ARCH_TIMER for the lowrisc,
sifive and ucb soc.

Change-Id: I5139601226e6f89da69e302a10f2fb56b4b24f38
Signed-off-by: Philipp Hug <philipp@hug.cx>
Reviewed-on: https://review.coreboot.org/27434
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/arch/riscv/arch_timer.c b/src/arch/riscv/arch_timer.c
new file mode 100644
index 0000000000..78157e6063
--- /dev/null
+++ b/src/arch/riscv/arch_timer.c
@@ -0,0 +1,28 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Philipp Hug <philipp@hug.cx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * 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.
+ */
+
+#include <arch/io.h>
+#include <arch/encoding.h>
+#include <console/console.h>
+#include <stddef.h>
+#include <timer.h>
+#include <mcall.h>
+
+void timer_monotonic_get(struct mono_time *mt)
+{
+	if (HLS()->time == NULL)
+		die("time not set in HLS");
+	mono_time_set_usecs(mt, (long)read64((void *)(HLS()->time)));
+}