[PATCH 2/5] ARM: bcm4760: Add system timer

[cavokz@gmail.com (Domenico Andreoli)]

On Sun, Jul 21, 2013 at 10:14:20AM +0200, Arnd Bergmann wrote:
> +Daniel Lezcano
> 
> On Sunday 21 July 2013, Domenico Andreoli wrote:
> 
> > 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
> 
> > +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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