RISC-V privileged architecture v1.10 defines a real-time counter,
exposed as a memory-mapped machine-mode register - mtime. mtime must
run at constant frequency, and the platform must provide a mechanism
for determining the timebase of mtime. The mtime register has a
64-bit precision on all RV32, RV64, and RV128 systems.
Different platform may have different implementation of the mtime
block hence an API riscv_get_time() is required by this driver for
platform codes to hide such implementation details. For example,
on some platforms mtime is provided by the CLINT module, while on
some other platforms a simple 'rdtime' can be used to get the timer
counter.
With this timer driver the U-Boot timer functionalities like delay
works correctly now.
Signed-off-by: Bin Meng <bmeng...@gmail.com>
Reviewed-by: Lukas Auer <lukas.a...@aisec.fraunhofer.de>
Reviewed-by: Anup Patel <a...@brainfault.org>
---
Changes in v5: None
Changes in v4: None
Changes in v3:
- remove 'select RISCV_CLINT' in Kconfig
- do not mention the spec version number v1.10
- adjust riscv_get_time() API signature to have a return value
Changes in v2:
- remove the probe to syscon driver in the timer probe, to make the
driver generic, and rely on platform codes to provide the API
riscv_get_time().
drivers/timer/Kconfig | 7 ++++++
drivers/timer/Makefile | 1 +
drivers/timer/riscv_timer.c | 56 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 64 insertions(+)
create mode 100644 drivers/timer/riscv_timer.c
diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
index b0e6f32..df37a79 100644
--- a/drivers/timer/Kconfig
+++ b/drivers/timer/Kconfig
@@ -126,6 +126,13 @@ config OMAP_TIMER
help
Select this to enable an timer for Omap devices.
+config RISCV_TIMER
+ bool "RISC-V timer support"
+ depends on TIMER && RISCV
+ help
+ Select this to enable support for the timer as defined
+ by the RISC-V privileged architecture spec.
+
config ROCKCHIP_TIMER
bool "Rockchip timer support"
depends on TIMER
diff --git a/drivers/timer/Makefile b/drivers/timer/Makefile
index c4fbab2..d0bf218 100644
--- a/drivers/timer/Makefile
+++ b/drivers/timer/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_CADENCE_TTC_TIMER) += cadence-ttc.o
obj-$(CONFIG_DESIGNWARE_APB_TIMER) += dw-apb-timer.o
obj-$(CONFIG_MPC83XX_TIMER) += mpc83xx_timer.o
obj-$(CONFIG_OMAP_TIMER) += omap-timer.o
+obj-$(CONFIG_RISCV_TIMER) += riscv_timer.o
obj-$(CONFIG_ROCKCHIP_TIMER) += rockchip_timer.o
obj-$(CONFIG_SANDBOX_TIMER) += sandbox_timer.o
obj-$(CONFIG_STI_TIMER) += sti-timer.o
diff --git a/drivers/timer/riscv_timer.c b/drivers/timer/riscv_timer.c
new file mode 100644
index 0000000..9f9f070
--- /dev/null
+++ b/drivers/timer/riscv_timer.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018, Bin Meng <bmeng...@gmail.com>
+ *
+ * RISC-V privileged architecture defined generic timer driver
+ *
+ * This driver relies on RISC-V platform codes to provide the essential API
+ * riscv_get_time() which is supposed to return the timer counter as defined
+ * by the RISC-V privileged architecture spec.
+ *
+ * This driver can be used in both M-mode and S-mode U-Boot.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <timer.h>
+#include <asm/io.h>
+
+/**
+ * riscv_get_time() - get the timer counter
+ *
+ * Platform codes should provide this API in order to make this driver
function.
+ *
+ * @time: the 64-bit timer count as defined by the RISC-V privileged
+ * architecture spec.
+ * @return: 0 on success, -ve on error.
+ */
+extern int riscv_get_time(u64 *time);
+
+static int riscv_timer_get_count(struct udevice *dev, u64 *count)
+{
+ return riscv_get_time(count);
+}
+
+static int riscv_timer_probe(struct udevice *dev)
+{
+ struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+
+ /* clock frequency was passed from the cpu driver as driver data */
+ uc_priv->clock_rate = dev->driver_data;
+
+ return 0;
+}
+
+static const struct timer_ops riscv_timer_ops = {
+ .get_count = riscv_timer_get_count,
+};
+
+U_BOOT_DRIVER(riscv_timer) = {
+ .name = "riscv_timer",
+ .id = UCLASS_TIMER,
+ .probe = riscv_timer_probe,
+ .ops = &riscv_timer_ops,
+ .flags = DM_FLAG_PRE_RELOC,
+};
--
2.7.4
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