[U-Boot] [PATCH v2 1/2] drivers: timer: Introduce ARC timer driver

[Vlad Zakharov]

This commit introduces timer driver for ARC.

ARC timers are configured via ARC AUX registers so we use special
functions to access timer control registers.

This driver allows utilization of either timer0 or timer1
depending on which one is available in real hardware. Essentially
only existing timers should be mentioned in board's Device Tree
description.

Signed-off-by: Vlad Zakharov <vzakhar at synopsys.com>
Reviewed-by: Simon Glass <sjg at chromium.org>
---
Changes v1..v2
 - Minor clean-ups of code and comments

 arch/arc/include/asm/arcregs.h               |  4 ++
 doc/device-tree-bindings/timer/arc_timer.txt | 24 +++++++
 drivers/timer/Kconfig                        | 10 +++
 drivers/timer/Makefile                       |  1 +
 drivers/timer/arc_timer.c                    | 99 ++++++++++++++++++++++++++++
 5 files changed, 138 insertions(+)
 create mode 100644 doc/device-tree-bindings/timer/arc_timer.txt
 create mode 100644 drivers/timer/arc_timer.c

diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index cf999b0..54a9b00 100644
--- a/arch/arc/include/asm/arcregs.h
+++ b/arch/arc/include/asm/arcregs.h
@@ -33,6 +33,10 @@
 #define ARC_AUX_TIMER0_CTRL	0x22	/* Timer 0 control */
 #define ARC_AUX_TIMER0_LIMIT	0x23	/* Timer 0 limit */
 
+#define ARC_AUX_TIMER1_CNT	0x100	/* Timer 1 count */
+#define ARC_AUX_TIMER1_CTRL	0x101	/* Timer 1 control */
+#define ARC_AUX_TIMER1_LIMIT	0x102	/* Timer 1 limit */
+
 #define ARC_AUX_INTR_VEC_BASE	0x25
 
 /* Data cache related auxiliary registers */
diff --git a/doc/device-tree-bindings/timer/arc_timer.txt b/doc/device-tree-bindings/timer/arc_timer.txt
new file mode 100644
index 0000000..e25c6ae
--- /dev/null
+++ b/doc/device-tree-bindings/timer/arc_timer.txt
@@ -0,0 +1,24 @@
+ARC Timer
+
+Required properties:
+
+- compatible : should be "snps,arc-timer"
+- reg : Specifies timer ID, could be either 0 or 1.
+- clock-frequency : The frequency of the clock that drives the counter, in Hz.
+
+Examples:
+
+timer at 0 {
+	compatible = "snps,arc-timer";
+	clock-frequency = <100000000>;
+	reg = <0>;
+};
+
+timer at 1 {
+	compatible = "snps,arc-timer";
+	clock-frequency = <100000000>;
+	reg = <1>;
+};
+
+NOTE: if you specify both timers, frequencies should always be the same as both timers
+are driven by core clock.
diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
index cb18f12..e1e3e61 100644
--- a/drivers/timer/Kconfig
+++ b/drivers/timer/Kconfig
@@ -46,4 +46,14 @@ config OMAP_TIMER
 	help
 	  Select this to enable an timer for Omap devices.
 
+config ARC_TIMER
+	bool "ARC timer support"
+	depends on TIMER
+	depends on ARC
+	help
+	  Select this to enable built-in ARC timers.
+	  ARC cores may have up to 2 built-in timers: timer0 and timer1,
+	  usually at least one of them exists. Either of them is supported
+	  in U-Boot.
+
 endmenu
diff --git a/drivers/timer/Makefile b/drivers/timer/Makefile
index f351fbb..e9624dd 100644
--- a/drivers/timer/Makefile
+++ b/drivers/timer/Makefile
@@ -9,3 +9,4 @@ obj-$(CONFIG_ALTERA_TIMER)	+= altera_timer.o
 obj-$(CONFIG_SANDBOX_TIMER)	+= sandbox_timer.o
 obj-$(CONFIG_X86_TSC_TIMER)	+= tsc_timer.o
 obj-$(CONFIG_OMAP_TIMER)	+= omap-timer.o
+obj-$(CONFIG_ARC_TIMER)	+= arc_timer.o
diff --git a/drivers/timer/arc_timer.c b/drivers/timer/arc_timer.c
new file mode 100644
index 0000000..c43ddd0
--- /dev/null
+++ b/drivers/timer/arc_timer.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2016 Synopsys, Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <timer.h>
+#include <asm/io.h>
+#include <asm/arcregs.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define NH_MODE (1 << 1)
+
+/*
+ * ARC timer control registers are mapped to auxiliary address space.
+ * There are special ARC asm command to access that addresses.
+ * Therefore we use built-in functions to read from and write to timer
+ * control register.
+ */
+
+/* Driver private data. Contains AUX register number. */
+struct arc_timer_priv {
+		uint timer_id;
+};
+
+static int arc_timer_get_count(struct udevice *dev, u64 *count)
+{
+	struct arc_timer_priv *priv = dev_get_priv(dev);
+	switch (priv->timer_id) {
+	case 0:
+		*count = read_aux_reg(ARC_AUX_TIMER0_CNT);
+		break;
+	case 1:
+		*count = read_aux_reg(ARC_AUX_TIMER1_CNT);
+		break;
+	}
+
+	return 0;
+}
+
+static int arc_timer_probe(struct udevice *dev)
+{
+	int id;
+
+	struct arc_timer_priv *priv = dev_get_priv(dev);
+
+	/* Get registers offset and size */
+	id = fdtdec_get_int(gd->fdt_blob, dev->of_offset, "reg", -1);
+	if (id < 0)
+		return -EINVAL;
+	if (id > 1)
+		return -ENXIO;
+
+	priv->timer_id = (uint)id;
+
+	switch (priv->timer_id) {
+	case 0:
+		/* Disable timer if CPU is halted */
+		write_aux_reg(ARC_AUX_TIMER0_CTRL, NH_MODE);
+		/* Set max value for counter/timer */
+		write_aux_reg(ARC_AUX_TIMER0_LIMIT, 0xffffffff);
+		/* Set initial count value and restart counter/timer */
+		write_aux_reg(ARC_AUX_TIMER0_CNT, 0);
+		break;
+	case 1:
+		/* Disable timer if CPU is halted */
+		write_aux_reg(ARC_AUX_TIMER1_CTRL, NH_MODE);
+		/* Set max value for counter/timer */
+		write_aux_reg(ARC_AUX_TIMER1_LIMIT, 0xffffffff);
+		/* Set initial count value and restart counter/timer */
+		write_aux_reg(ARC_AUX_TIMER1_CNT, 0);
+		break;
+	}
+
+	return 0;
+}
+
+
+static const struct timer_ops arc_timer_ops = {
+	.get_count = arc_timer_get_count,
+};
+
+static const struct udevice_id arc_timer_ids[] = {
+	{ .compatible = "snps,arc-timer" },
+	{}
+};
+
+U_BOOT_DRIVER(arc_timer) = {
+	.name	= "arc_timer",
+	.id	= UCLASS_TIMER,
+	.of_match = arc_timer_ids,
+	.probe = arc_timer_probe,
+	.ops	= &arc_timer_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};
-- 
2.7.4