/*
 * Copyright (c) 2018 Henrik Brix Andersen <henrik@brixandersen.dk>
 * Copyright (c) 2017 Google LLC.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <soc.h>
#include <watchdog.h>

#define LOG_LEVEL CONFIG_WDT_LOG_LEVEL
#include <logging/log.h>
LOG_MODULE_REGISTER(wdt_sam0);

#define WDT_REGS ((Wdt *)DT_WDT_SAM0_BASE_ADDRESS)

struct wdt_sam0_dev_data {
	wdt_callback_t cb;
	bool timeout_valid;
};

static struct device DEVICE_NAME_GET(wdt_sam0);

static struct wdt_sam0_dev_data wdt_sam0_data = { 0 };

static void wdt_sam0_wait_synchronization(void)
{
	while (WDT_REGS->STATUS.bit.SYNCBUSY) {
	}
}

static u32_t wdt_sam0_timeout_to_wdt_period(u32_t timeout_ms)
{
	u32_t next_pow2;
	u32_t cycles;

	/* Calculate number of clock cycles @ 1.024 kHz input clock */
	cycles = (timeout_ms * 1024) / 1000;

	/* Minimum wdt period is 8 clock cycles (register value 0) */
	if (cycles <= 8)
		return 0;

	/* Round up to next pow2 and calculate the register value */
	next_pow2 = (1ULL << 32) >> __builtin_clz(cycles - 1);
	return find_msb_set(next_pow2 >> 4);
}

static void wdt_sam0_isr(struct device *dev)
{
	struct wdt_sam0_dev_data *data = dev->driver_data;

	WDT_REGS->INTFLAG.reg = WDT_INTFLAG_EW;
	if (data->cb != NULL) {
		data->cb(dev, 0);
	}
}

static int wdt_sam0_setup(struct device *dev, u8_t options)
{
	struct wdt_sam0_dev_data *data = dev->driver_data;

	if (WDT_REGS->CTRL.reg == WDT_CTRL_ENABLE) {
		LOG_ERR("Watchdog already setup");
		return -EBUSY;
	}

	if (!data->timeout_valid) {
		LOG_ERR("No valid timeout installed");
		return -EINVAL;
	}

	if (options & WDT_OPT_PAUSE_IN_SLEEP) {
		LOG_ERR("Pause in sleep not supported");
		return -ENOTSUP;
	}

	if (options & WDT_OPT_PAUSE_HALTED_BY_DBG) {
		LOG_ERR("Pause when halted by debugger not supported");
		return -ENOTSUP;
	}

	/* Enable watchdog */
	WDT_REGS->CTRL.bit.ENABLE = 1;
	wdt_sam0_wait_synchronization();

	return 0;
}

static int wdt_sam0_disable(struct device *dev)
{
	if (!WDT_REGS->CTRL.bit.ENABLE) {
		LOG_ERR("Watchdog not enabled");
		return -EFAULT;
	}

	WDT_REGS->CTRL.bit.ENABLE = 0;
	wdt_sam0_wait_synchronization();

	return 0;
}

static int wdt_sam0_install_timeout(struct device *dev,
				const struct wdt_timeout_cfg *cfg)
{
	struct wdt_sam0_dev_data *data = dev->driver_data;
	u32_t window, per;

	/* CONFIG is enable protected, error out if already enabled */
	if (WDT_REGS->CTRL.bit.ENABLE) {
		LOG_ERR("Watchdog already setup");
		return -EBUSY;
	}

	if (cfg->flags != WDT_FLAG_RESET_SOC) {
		LOG_ERR("Only SoC reset supported");
		return -ENOTSUP;
	}

	per = wdt_sam0_timeout_to_wdt_period(cfg->window.max);
	if (per > WDT_CONFIG_PER_16K_Val) {
		LOG_ERR("Upper limit timeout out of range");
		goto timeout_invalid;
	}

	if (cfg->window.min) {
		/* Window mode */
		window = wdt_sam0_timeout_to_wdt_period(cfg->window.min);
		if (window > WDT_CONFIG_PER_8K_Val) {
			LOG_ERR("Lower limit timeout out of range");
			goto timeout_invalid;
		}
		if (per <= window) {
			/* Ensure we have a window */
			per = window + 1;
		}
		WDT_REGS->CTRL.bit.WEN = 1;
		wdt_sam0_wait_synchronization();
	} else {
		/* Normal mode */
		if (cfg->callback) {
			if (per == WDT_CONFIG_PER_8_Val) {
				/* Ensure we have time for the early warning */
				per += 1;
			}
			WDT_REGS->EWCTRL.bit.EWOFFSET = per - 1;
		}
		window = WDT_CONFIG_PER_8_Val;
		WDT_REGS->CTRL.bit.WEN = 0;
		wdt_sam0_wait_synchronization();
	}

	WDT_REGS->CONFIG.reg = WDT_CONFIG_WINDOW(window) | WDT_CONFIG_PER(per);
	wdt_sam0_wait_synchronization();

	/* Only enable IRQ if a callback was provided */
	data->cb = cfg->callback;
	if (data->cb) {
		WDT_REGS->INTENSET.reg = WDT_INTENSET_EW;
	} else {
		WDT_REGS->INTENCLR.reg = WDT_INTENCLR_EW;
		WDT_REGS->INTFLAG.reg = WDT_INTFLAG_EW;
	}

	data->timeout_valid = true;

	return 0;

timeout_invalid:
	data->timeout_valid = false;
	data->cb = NULL;

	return -EINVAL;
}

static int wdt_sam0_feed(struct device *dev, int channel_id)
{
	struct wdt_sam0_dev_data *data = dev->driver_data;

	if (!data->timeout_valid) {
		LOG_ERR("No valid timeout installed");
		return -EINVAL;
	}

	WDT_REGS->CLEAR.reg = WDT_CLEAR_CLEAR_KEY_Val;

	return 0;
}

static const struct wdt_driver_api wdt_sam0_api = {
	.setup = wdt_sam0_setup,
	.disable = wdt_sam0_disable,
	.install_timeout = wdt_sam0_install_timeout,
	.feed = wdt_sam0_feed,
};

static int wdt_sam0_init(struct device *dev)
{
#ifdef CONFIG_WDT_DISABLE_AT_BOOT
	/* Ignore any errors */
	wdt_sam0_disable(dev);
#endif
	/* Enable APB clock */
	PM->APBAMASK.bit.WDT_ = 1;

	/* Connect to GCLK2 (~1.024 kHz) */
	GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID_WDT
		| GCLK_CLKCTRL_GEN_GCLK2
		| GCLK_CLKCTRL_CLKEN;

	IRQ_CONNECT(DT_WDT_SAM0_IRQ,
		    DT_WDT_SAM0_IRQ_PRIORITY, wdt_sam0_isr,
		    DEVICE_GET(wdt_sam0), 0);
	irq_enable(DT_WDT_SAM0_IRQ);

	return 0;
}

static struct wdt_sam0_dev_data wdt_sam0_data;

DEVICE_AND_API_INIT(wdt_sam0, DT_WDT_SAM0_LABEL, wdt_sam0_init,
		    &wdt_sam0_data, NULL, PRE_KERNEL_1,
		    CONFIG_KERNEL_INIT_PRIORITY_DEVICE, &wdt_sam0_api);