On Sun, Jul 21, 2013 at 10:14:20AM +0200, Arnd Bergmann wrote:

+Daniel Lezcano

On Sunday 21 July 2013, Domenico Andreoli wrote:

quoted

Index: b/Documentation/devicetree/bindings/timer/brcm,bcm4760-system-timer.txt
===================================================================

--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/brcm,bcm4760-system-timer.txt

@@ -0,0 +1,23 @@
+Broadcom BCM4760 System Timer device tree bindings
+--------------------------------------------------
+
+The BCM4760 Timer peripheral provides either two or four 32-bit timer
+channels. Three timer blocks are available at 0xba000, 0xbb000 and
+0xd1000. The first two provide four channels, the last (in the AON -
+Always ON power domain) provides only two.
+
+Required properties:
+
+- compatible : should be "brcm,bcm4760-system-timer"
+- reg : Specifies base physical address and size of the registers.
+- interrupts : A list of 2 or 4 interrupt sinks; one per timer channel.
+- clock-frequency : The frequency of the clock that drives the counter, in Hz.

I think the current consensus is that if you have a clock driver (as added in
patch 4), you should use a 'clocks' reference and clk_get_rate() to find the
frequency rather than an explicit clock-frequency property.

This frequency can be either 32KHz or 24MHz (currently only 24MHz is
accepted) and is selected flipping bit TIMER_CTRL_CLK2 in the timer's control
register. It depends somehow on the pclk but I don't know the details.

I'm not sure a fake fixed-rate clock is needed here. Do you still think
I should add it? 

Domenico

I have no comments on the driver, the rest is quoted so Daniel can find it
more easily.

	Arnd

quoted

+Example:
+
+timer at ba000 {
+	compatible = "brcm,bcm4760-system-timer";
+	reg = <0xba000 0x1000>;
+	interrupts = <4>, <11>;
+	clock-frequency = <24000000>;
+};
Index: b/arch/arm/boot/dts/bcm4760.dtsi
===================================================================

--- a/arch/arm/boot/dts/bcm4760.dtsi
+++ b/arch/arm/boot/dts/bcm4760.dtsi

@@ -10,6 +10,14 @@
 		#size-cells = <1>;
 		ranges;
 
+		timer at ba000 {
+			compatible = "brcm,bcm4760-system-timer";
+			reg = <0xba000 0x1000>;
+			interrupt-parent = <&vic0>;
+			interrupts = <4>, <11>;
+			clock-frequency = <24000000>;
+		};
+
 		vic0: interrupt-controller at 80000 {
 			compatible = "brcm,bcm4760-pl192", "arm,pl192-vic", "arm,primecell";
 			reg = <0x80000 0x1000>;

Index: b/drivers/clocksource/Makefile
===================================================================

--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile

@@ -17,6 +17,7 @@ obj-$(CONFIG_CLKSRC_DBX500_PRCMU)	+= clk
 obj-$(CONFIG_ARMADA_370_XP_TIMER)	+= time-armada-370-xp.o
 obj-$(CONFIG_ORION_TIMER)	+= time-orion.o
 obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835_timer.o
+obj-$(CONFIG_ARCH_BCM4760)	+= bcm4760_timer.o
 obj-$(CONFIG_ARCH_MARCO)	+= timer-marco.o
 obj-$(CONFIG_ARCH_MXS)		+= mxs_timer.o
 obj-$(CONFIG_ARCH_PRIMA2)	+= timer-prima2.o

Index: b/drivers/clocksource/bcm4760_timer.c
===================================================================

--- /dev/null
+++ b/drivers/clocksource/bcm4760_timer.c

@@ -0,0 +1,170 @@
+/*
+ * Broadcom BCM4760 based ARM11 SoCs system timer
+ *
+ * Copyright (C) 2012 Domenico Andreoli <domenico.andreoli@linux.com>
+ *
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/clockchips.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+
+#define TIMER_LOAD_OFFSET          0x00          /* load */
+#define TIMER_VALUE_OFFSET         0x04          /* value */
+#define TIMER_CONTROL_OFFSET       0x08          /* control */
+#define TIMER_INTCLR_OFFSET        0x0c          /* interrupt clear */
+#define TIMER_RIS_OFFSET           0x10          /* raw interrupt */
+#define TIMER_MIS_OFFSET           0x14          /* masked interrupt status */
+#define TIMER_BGLOAD_OFFSET        0x18          /* background load */
+
+#define TIMER_CTRL_ONESHOTMODE     BIT(0)        /* One shot mode */
+#define TIMER_CTRL_32BIT           BIT(1)        /* 32-bit counter mode */
+#define TIMER_CTRL_IE              BIT(5)        /* Interrupt enable */
+#define TIMER_CTRL_PERIODIC        BIT(6)        /* Periodic mode */
+#define TIMER_CTRL_EN              BIT(7)        /* Timer enable */
+#define TIMER_CTRL_CLK2            BIT(9)        /* Clock 2 selected */
+#define TIMER_CTRL_PREBY16         (1 << 2)      /* prescale divide by 16 */
+#define TIMER_CTRL_PREBY256        (2 << 2)      /* prescale divide by 256 */
+
+struct bcm4760_timer {
+	void __iomem *base;
+	struct clock_event_device evt;
+	struct irqaction act;
+};
+
+static inline void __iomem *to_load(struct bcm4760_timer *timer)
+{
+	return timer->base + TIMER_LOAD_OFFSET;
+}
+
+static inline void __iomem *to_control(struct bcm4760_timer *timer)
+{
+	return timer->base + TIMER_CONTROL_OFFSET;
+}
+
+static inline void __iomem *to_intclr(struct bcm4760_timer *timer)
+{
+	return timer->base + TIMER_INTCLR_OFFSET;
+}
+
+static inline void __iomem *to_ris(struct bcm4760_timer *timer)
+{
+	return timer->base + TIMER_RIS_OFFSET;
+}
+
+static inline void __iomem *to_mis(struct bcm4760_timer *timer)
+{
+	return timer->base + TIMER_MIS_OFFSET;
+}
+
+static void bcm4760_timer_set_mode(enum clock_event_mode mode,
+	struct clock_event_device *evt_dev)
+{
+	struct bcm4760_timer *timer;
+	u32 val;
+
+	timer = container_of(evt_dev, struct bcm4760_timer, evt);
+	val = TIMER_CTRL_CLK2 | TIMER_CTRL_32BIT |
+	      TIMER_CTRL_IE | TIMER_CTRL_EN;
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_ONESHOT:
+		writel(val | TIMER_CTRL_ONESHOTMODE, to_control(timer));
+		break;
+	case CLOCK_EVT_MODE_RESUME:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		break;
+	default:
+		WARN(1, "%s: unhandled event mode %d\n", __func__, mode);
+		break;
+	}
+}
+
+static int bcm4760_timer_set_next_event(unsigned long event,
+	struct clock_event_device *evt_dev)
+{
+	struct bcm4760_timer *timer;
+
+	timer = container_of(evt_dev, struct bcm4760_timer, evt);
+	writel(event, to_load(timer));
+	return 0;
+}
+
+static irqreturn_t bcm4760_timer_interrupt(int irq, void *dev_id)
+{
+	struct bcm4760_timer *timer = dev_id;
+	void (*event_handler)(struct clock_event_device *);
+
+	/* check the (masked) interrupt status */
+	if (!readl_relaxed(to_mis(timer)))
+		return IRQ_NONE;
+
+	/* clear the timer interrupt */
+	writel_relaxed(1, to_intclr(timer));
+
+	event_handler = ACCESS_ONCE(timer->evt.event_handler);
+	if (event_handler)
+		event_handler(&timer->evt);
+
+	return IRQ_HANDLED;
+}
+
+static void __init bcm4760_init_time(struct device_node *node)
+{
+	void __iomem *base;
+	u32 freq;
+	int irq;
+	struct bcm4760_timer *timer;
+
+	base = of_iomap(node, 0);
+	if (!base)
+		panic("Can't remap timer registers");
+
+	if (of_property_read_u32(node, "clock-frequency", &freq))
+		panic("Can't read timer frequency");
+
+	/* TODO allow other frequences by using pre-scaling parameters */
+	if (freq != 24000000)
+		panic("Invalid timer frequency");
+
+	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
+	if (!timer)
+		panic("Can't allocate timer struct\n");
+
+	irq = irq_of_parse_and_map(node, 0);
+	if (irq <= 0)
+		panic("Can't parse timer IRQ");
+
+	timer->base = base;
+	timer->evt.name = node->name;
+	timer->evt.rating = 300;
+	timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
+	timer->evt.set_mode = bcm4760_timer_set_mode;
+	timer->evt.set_next_event = bcm4760_timer_set_next_event;
+	timer->evt.cpumask = cpumask_of(0);
+	timer->act.name = node->name;
+	timer->act.flags = IRQF_TIMER | IRQF_SHARED;
+	timer->act.dev_id = timer;
+	timer->act.handler = bcm4760_timer_interrupt;
+
+	if (setup_irq(irq, &timer->act))
+		panic("Can't set up timer IRQ\n");
+
+	clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
+}
+
+CLOCKSOURCE_OF_DECLARE(bcm4760, "brcm,bcm4760-system-timer", bcm4760_init_time);

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