clocksource: timer-keystone: introduce clocksource driver for Keystone

obj-$(CONFIG_ARM_GLOBAL_TIMER)		+= arm_global_timer.o

obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o

obj-$(CONFIG_ARCH_HAS_TICK_BROADCAST)	+= dummy_timer.o

obj-$(CONFIG_ARCH_KEYSTONE)		+= timer-keystone.o

/*

 * Keystone broadcast clock-event

 *

 * Copyright 2013 Texas Instruments, Inc.

 *

 * Author: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 */

#include <linux/clk.h>

#include <linux/clockchips.h>

#include <linux/clocksource.h>

#include <linux/interrupt.h>

#include <linux/of_address.h>

#include <linux/of_irq.h>

#define TIMER_NAME			"timer-keystone"

/* Timer register offsets */

#define TIM12				0x10

#define TIM34				0x14

#define PRD12				0x18

#define PRD34				0x1c

#define TCR				0x20

#define TGCR				0x24

#define INTCTLSTAT			0x44

/* Timer register bitfields */

#define TCR_ENAMODE_MASK		0xC0

#define TCR_ENAMODE_ONESHOT_MASK	0x40

#define TCR_ENAMODE_PERIODIC_MASK	0x80

#define TGCR_TIM_UNRESET_MASK		0x03

#define INTCTLSTAT_ENINT_MASK		0x01

/**

 * struct keystone_timer: holds timer's data

 * @base: timer memory base address

 * @hz_period: cycles per HZ period

 * @event_dev: event device based on timer

 */

static struct keystone_timer {

	void __iomem *base;

	unsigned long hz_period;

	struct clock_event_device event_dev;

} timer;

static inline u32 keystone_timer_readl(unsigned long rg)

{

	return readl_relaxed(timer.base + rg);

}

static inline void keystone_timer_writel(u32 val, unsigned long rg)

{

	writel_relaxed(val, timer.base + rg);

}

/**

 * keystone_timer_barrier: write memory barrier

 * use explicit barrier to avoid using readl/writel non relaxed function

 * variants, because in our case non relaxed variants hide the true places

 * where barrier is needed.

 */

static inline void keystone_timer_barrier(void)

{

	__iowmb();

}

/**

 * keystone_timer_config: configures timer to work in oneshot/periodic modes.

 * @ mode: mode to configure

 * @ period: cycles number to configure for

 */

static int keystone_timer_config(u64 period, enum clock_event_mode mode)

{

	u32 tcr;

	u32 off;

	tcr = keystone_timer_readl(TCR);

	off = tcr & ~(TCR_ENAMODE_MASK);

	/* set enable mode */

	switch (mode) {

	case CLOCK_EVT_MODE_ONESHOT:

		tcr |= TCR_ENAMODE_ONESHOT_MASK;

		break;

	case CLOCK_EVT_MODE_PERIODIC:

		tcr |= TCR_ENAMODE_PERIODIC_MASK;

		break;

	default:

		return -1;

	}

	/* disable timer */

	keystone_timer_writel(off, TCR);

	/* here we have to be sure the timer has been disabled */

	keystone_timer_barrier();

	/* reset counter to zero, set new period */

	keystone_timer_writel(0, TIM12);

	keystone_timer_writel(0, TIM34);

	keystone_timer_writel(period & 0xffffffff, PRD12);

	keystone_timer_writel(period >> 32, PRD34);

	/*

	 * enable timer

	 * here we have to be sure that CNTLO, CNTHI, PRDLO, PRDHI registers

	 * have been written.

	 */

	keystone_timer_barrier();

	keystone_timer_writel(tcr, TCR);

	return 0;

}

static void keystone_timer_disable(void)

{

	u32 tcr;

	tcr = keystone_timer_readl(TCR);

	/* disable timer */

	tcr &= ~(TCR_ENAMODE_MASK);

	keystone_timer_writel(tcr, TCR);

}

static irqreturn_t keystone_timer_interrupt(int irq, void *dev_id)

{

	struct clock_event_device *evt = dev_id;

	evt->event_handler(evt);

	return IRQ_HANDLED;

}

static int keystone_set_next_event(unsigned long cycles,

				  struct clock_event_device *evt)

{

	return keystone_timer_config(cycles, evt->mode);

}

static void keystone_set_mode(enum clock_event_mode mode,

			     struct clock_event_device *evt)

{

	switch (mode) {

	case CLOCK_EVT_MODE_PERIODIC:

		keystone_timer_config(timer.hz_period, CLOCK_EVT_MODE_PERIODIC);

		break;

	case CLOCK_EVT_MODE_UNUSED:

	case CLOCK_EVT_MODE_SHUTDOWN:

	case CLOCK_EVT_MODE_ONESHOT:

		keystone_timer_disable();

		break;

	default:

		break;

	}

}

static void __init keystone_timer_init(struct device_node *np)

{

	struct clock_event_device *event_dev = &timer.event_dev;

	unsigned long rate;

	struct clk *clk;

	int irq, error;

	u32 tgcr;

	irq  = irq_of_parse_and_map(np, 0);

	if (irq == NO_IRQ) {

		pr_err("%s: failed to map interrupts\n", __func__);

		return;

	}

	timer.base = of_iomap(np, 0);

	if (!timer.base) {

		pr_err("%s: failed to map registers\n", __func__);

		return;

	}

	clk = of_clk_get(np, 0);

	if (IS_ERR(clk)) {

		pr_err("%s: failed to get clock\n", __func__);

		iounmap(timer.base);

		return;

	}

	error = clk_prepare_enable(clk);

	if (error) {

		pr_err("%s: failed to enable clock\n", __func__);

		goto err;

	}

	rate = clk_get_rate(clk);

	/* disable, use internal clock source */

	keystone_timer_writel(0, TCR);

	/* here we have to be sure the timer has been disabled */

	keystone_timer_barrier();

	/* reset timer as 64-bit, no pre-scaler, plus features are disabled */

	tgcr = 0;

	keystone_timer_writel(0, TGCR);

	/* unreset timer */

	tgcr |= TGCR_TIM_UNRESET_MASK;

	keystone_timer_writel(tgcr, TGCR);

	/* init counter to zero */

	keystone_timer_writel(0, TIM12);

	keystone_timer_writel(0, TIM34);

	timer.hz_period = DIV_ROUND_UP(rate, HZ);

	/* enable timer interrupts */

	keystone_timer_writel(INTCTLSTAT_ENINT_MASK, INTCTLSTAT);

	error = request_irq(irq, keystone_timer_interrupt, IRQF_TIMER,

			    TIMER_NAME, event_dev);

	if (error) {

		pr_err("%s: failed to setup irq\n", __func__);

		goto err;

	}

	/* setup clockevent */

	event_dev->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;

	event_dev->set_next_event = keystone_set_next_event;

	event_dev->set_mode = keystone_set_mode;

	event_dev->cpumask = cpu_all_mask;

	event_dev->owner = THIS_MODULE;

	event_dev->name = TIMER_NAME;

	event_dev->irq = irq;

	clockevents_config_and_register(event_dev, rate, 1, ULONG_MAX);

	pr_info("keystone timer clock @%lu Hz\n", rate);

	return;

err:

	clk_put(clk);

	iounmap(timer.base);

}

CLOCKSOURCE_OF_DECLARE(keystone_timer, "ti,keystone-timer",

					keystone_timer_init);