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>

5 files changed, 48 insertions, 4 deletions

diff --git a/src/arch/riscv/Kconfig b/src/arch/riscv/Kconfig
index 916e269b32..2d53f422c1 100644
--- a/src/arch/riscv/Kconfig
+++ b/src/arch/riscv/Kconfig
@@ -28,3 +28,7 @@ config ARCH_ROMSTAGE_RISCV
 config ARCH_RAMSTAGE_RISCV
 	bool
 	default n
+
+config RISCV_USE_ARCH_TIMER
+	bool
+	default n
diff --git a/src/arch/riscv/Makefile.inc b/src/arch/riscv/Makefile.inc
index f4b69bb95e..50c1ae69d6 100644
--- a/src/arch/riscv/Makefile.inc
+++ b/src/arch/riscv/Makefile.inc
@@ -56,6 +56,8 @@ bootblock-y += \
 	$(top)/src/lib/memmove.c \
 	$(top)/src/lib/memset.c
 
+bootblock-$(CONFIG_RISCV_USE_ARCH_TIMER) += arch_timer.c
+
 $(objcbfs)/bootblock.debug: $$(bootblock-objs)
 	@printf "    LINK       $(subst $(obj)/,,$(@))\n"
 	$(LD_bootblock) $(LDFLAGS_bootblock) -o $@ -L$(obj) \
@@ -82,6 +84,8 @@ romstage-y += \
 	$(top)/src/lib/memmove.c \
 	$(top)/src/lib/memset.c
 
+romstage-$(CONFIG_RISCV_USE_ARCH_TIMER) += arch_timer.c
+
 # Build the romstage
 
 $(objcbfs)/romstage.debug: $$(romstage-objs)
@@ -118,6 +122,8 @@ ramstage-y += \
 	$(top)/src/lib/memmove.c \
 	$(top)/src/lib/memset.c
 
+ramstage-$(CONFIG_RISCV_USE_ARCH_TIMER) += arch_timer.c
+
 $(eval $(call create_class_compiler,rmodules,riscv))
 
 ramstage-srcs += src/mainboard/$(MAINBOARDDIR)/mainboard.c
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)));
+}
diff --git a/src/arch/riscv/include/arch/io.h b/src/arch/riscv/include/arch/io.h
index 5f66a239b4..6fd0cac88e 100644
--- a/src/arch/riscv/include/arch/io.h
+++ b/src/arch/riscv/include/arch/io.h
@@ -33,6 +33,11 @@ static __always_inline uint32_t read32(const volatile void *addr)
 	return *((volatile uint32_t *)(addr));
 }
 
+static __always_inline uint64_t read64(const volatile void *addr)
+{
+	return *((volatile uint64_t *)(addr));
+}
+
 static __always_inline void write8(volatile void *addr, uint8_t value)
 {
 	*((volatile uint8_t *)(addr)) = value;
@@ -48,4 +53,9 @@ static __always_inline void write32(volatile void *addr, uint32_t value)
 	*((volatile uint32_t *)(addr)) = value;
 }
 
+static __always_inline void write64(volatile void *addr, uint64_t value)
+{
+	*((volatile uint64_t *)(addr)) = value;
+}
+
 #endif
diff --git a/src/arch/riscv/misc.c b/src/arch/riscv/misc.c
index 65b8ecf02f..1909dbc5f1 100644
--- a/src/arch/riscv/misc.c
+++ b/src/arch/riscv/misc.c
@@ -16,7 +16,3 @@
 void init_timer(void)
 {
 }
-
-void udelay(unsigned int n)
-{
-}