/*
 * Copyright 2016 Freescale Semiconductor, Inc.
 * Copyright 2017 NXP
 *
 * 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.
 */

#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/sched_clock.h>

#define TPM_SC				0x10
#define TPM_SC_CMOD_INC_PER_CNT		(0x1 << 3)
#define TPM_SC_CMOD_DIV_DEFAULT		0x3
#define TPM_CNT				0x14
#define TPM_MOD				0x18
#define TPM_STATUS			0x1c
#define TPM_STATUS_CH0F			BIT(0)
#define TPM_C0SC			0x20
#define TPM_C0SC_CHIE			BIT(6)
#define TPM_C0SC_MODE_SHIFT		2
#define TPM_C0SC_MODE_MASK		0x3c
#define TPM_C0SC_MODE_SW_COMPARE	0x4
#define TPM_C0V				0x24

static void __iomem *timer_base;
static struct clock_event_device clockevent_tpm;

static inline void tpm_timer_disable(void)
{
	unsigned int val;

	/* channel disable */
	val = readl(timer_base + TPM_C0SC);
	val &= ~(TPM_C0SC_MODE_MASK | TPM_C0SC_CHIE);
	writel(val, timer_base + TPM_C0SC);
}

static inline void tpm_timer_enable(void)
{
	unsigned int val;

	/* channel enabled in sw compare mode */
	val = readl(timer_base + TPM_C0SC);
	val |= (TPM_C0SC_MODE_SW_COMPARE << TPM_C0SC_MODE_SHIFT) |
	       TPM_C0SC_CHIE;
	writel(val, timer_base + TPM_C0SC);
}

static inline void tpm_irq_acknowledge(void)
{
	writel(TPM_STATUS_CH0F, timer_base + TPM_STATUS);
}

static struct delay_timer tpm_delay_timer;

static inline unsigned long tpm_read_counter(void)
{
	return readl(timer_base + TPM_CNT);
}

static unsigned long tpm_read_current_timer(void)
{
	return tpm_read_counter();
}

static u64 notrace tpm_read_sched_clock(void)
{
	return tpm_read_counter();
}

static int __init tpm_clocksource_init(unsigned long rate)
{
	tpm_delay_timer.read_current_timer = &tpm_read_current_timer;
	tpm_delay_timer.freq = rate;
	register_current_timer_delay(&tpm_delay_timer);

	sched_clock_register(tpm_read_sched_clock, 32, rate);

	return clocksource_mmio_init(timer_base + TPM_CNT, "imx-tpm",
				     rate, 200, 32, clocksource_mmio_readl_up);
}

static int tpm_set_next_event(unsigned long delta,
				struct clock_event_device *evt)
{
	unsigned long next, now;

	next = tpm_read_counter();
	next += delta;
	writel(next, timer_base + TPM_C0V);
	now = tpm_read_counter();

	/*
	 * NOTE: We observed in a very small probability, the bus fabric
	 * contention between GPU and A7 may results a few cycles delay
	 * of writing CNT registers which may cause the min_delta event got
	 * missed, so we need add a ETIME check here in case it happened.
	 */
	return (int)((next - now) <= 0) ? -ETIME : 0;
}

static int tpm_set_state_oneshot(struct clock_event_device *evt)
{
	tpm_timer_enable();

	return 0;
}

static int tpm_set_state_shutdown(struct clock_event_device *evt)
{
	tpm_timer_disable();

	return 0;
}

static irqreturn_t tpm_timer_interrupt(int irq, void *dev_id)
{
	struct clock_event_device *evt = dev_id;

	tpm_irq_acknowledge();

	evt->event_handler(evt);

	return IRQ_HANDLED;
}

static struct clock_event_device clockevent_tpm = {
	.name			= "i.MX7ULP TPM Timer",
	.features		= CLOCK_EVT_FEAT_ONESHOT,
	.set_state_oneshot	= tpm_set_state_oneshot,
	.set_next_event		= tpm_set_next_event,
	.set_state_shutdown	= tpm_set_state_shutdown,
	.rating			= 200,
};

static int __init tpm_clockevent_init(unsigned long rate, int irq)
{
	int ret;

	ret = request_irq(irq, tpm_timer_interrupt, IRQF_TIMER | IRQF_IRQPOLL,
			  "i.MX7ULP TPM Timer", &clockevent_tpm);

	clockevent_tpm.cpumask = cpumask_of(0);
	clockevent_tpm.irq = irq;
	clockevents_config_and_register(&clockevent_tpm,
					rate, 300, 0xfffffffe);

	return ret;
}

static int __init tpm_timer_init(struct device_node *np)
{
	struct clk *ipg, *per;
	int irq, ret;
	u32 rate;

	timer_base = of_iomap(np, 0);
	if (!timer_base) {
		pr_err("tpm: failed to get base address\n");
		return -ENXIO;
	}

	irq = irq_of_parse_and_map(np, 0);
	if (!irq) {
		pr_err("tpm: failed to get irq\n");
		ret = -ENOENT;
		goto err_iomap;
	}

	ipg = of_clk_get_by_name(np, "ipg");
	per = of_clk_get_by_name(np, "per");
	if (IS_ERR(ipg) || IS_ERR(per)) {
		pr_err("tpm: failed to get igp or per clk\n");
		ret = -ENODEV;
		goto err_clk_get;
	}

	/* enable clk before accessing registers */
	ret = clk_prepare_enable(ipg);
	if (ret) {
		pr_err("tpm: ipg clock enable failed (%d)\n", ret);
		goto err_clk_get;
	}

	ret = clk_prepare_enable(per);
	if (ret) {
		pr_err("tpm: per clock enable failed (%d)\n", ret);
		goto err_per_clk_enable;
	}

	/*
	 * Initialize tpm module to a known state
	 * 1) Counter disabled
	 * 2) TPM counter operates in up counting mode
	 * 3) Timer Overflow Interrupt disabled
	 * 4) Channel0 disabled
	 * 5) DMA transfers disabled
	 */
	writel(0, timer_base + TPM_SC);
	writel(0, timer_base + TPM_CNT);
	writel(0, timer_base + TPM_C0SC);

	/* increase per cnt, div 8 by default */
	writel(TPM_SC_CMOD_INC_PER_CNT | TPM_SC_CMOD_DIV_DEFAULT,
		     timer_base + TPM_SC);

	/* set MOD register to maximum for free running mode */
	writel(0xffffffff, timer_base + TPM_MOD);

	rate = clk_get_rate(per) >> 3;
	ret = tpm_clocksource_init(rate);
	if (ret)
		goto err_per_clk_enable;

	ret = tpm_clockevent_init(rate, irq);
	if (ret)
		goto err_per_clk_enable;

	return 0;

err_per_clk_enable:
	clk_disable_unprepare(ipg);
err_clk_get:
	clk_put(per);
	clk_put(ipg);
err_iomap:
	iounmap(timer_base);
	return ret;
}
TIMER_OF_DECLARE(imx7ulp, "fsl,imx7ulp-tpm", tpm_timer_init);