/*
 * Copyright (c) 2017 Jean-Paul Etienne <fractalclone@gmail.com>
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @brief UART driver for the SiFive Freedom Processor
 */

#include <kernel.h>
#include <arch/cpu.h>
#include <drivers/uart.h>

#define RXDATA_EMPTY   (1 << 31)   /* Receive FIFO Empty */
#define RXDATA_MASK    0xFF        /* Receive Data Mask */

#define TXDATA_FULL    (1 << 31)   /* Transmit FIFO Full */

#define TXCTRL_TXEN    (1 << 0)    /* Activate Tx Channel */

#define RXCTRL_RXEN    (1 << 0)    /* Activate Rx Channel */

#define IE_TXWM        (1 << 0)    /* TX Interrupt Enable/Pending */
#define IE_RXWM        (1 << 1)    /* RX Interrupt Enable/Pending */

/*
 * RX/TX Threshold count to generate TX/RX Interrupts.
 * Used by txctrl and rxctrl registers
 */
#define CTRL_CNT(x)    (((x) & 0x07) << 16)

struct uart_sifive_regs_t {
	u32_t tx;
	u32_t rx;
	u32_t txctrl;
	u32_t rxctrl;
	u32_t ie;
	u32_t ip;
	u32_t div;
};

#ifdef CONFIG_UART_INTERRUPT_DRIVEN
typedef void (*irq_cfg_func_t)(void);
#endif

struct uart_sifive_device_config {
	uintptr_t   port;
	u32_t       sys_clk_freq;
	u32_t       baud_rate;
	u32_t       rxcnt_irq;
	u32_t       txcnt_irq;
#ifdef CONFIG_UART_INTERRUPT_DRIVEN
	irq_cfg_func_t cfg_func;
#endif
};

struct uart_sifive_data {
#ifdef CONFIG_UART_INTERRUPT_DRIVEN
	uart_irq_callback_user_data_t callback;
	void *cb_data;
#endif
};

#define DEV_CFG(dev)						\
	((const struct uart_sifive_device_config * const)	\
	 (dev)->config->config_info)
#define DEV_UART(dev)						\
	((struct uart_sifive_regs_t *)(DEV_CFG(dev))->port)
#define DEV_DATA(dev)						\
	((struct uart_sifive_data * const)(dev)->driver_data)

/**
 * @brief Output a character in polled mode.
 *
 * Writes data to tx register if transmitter is not full.
 *
 * @param dev UART device struct
 * @param c Character to send
 */
static void uart_sifive_poll_out(struct device *dev,
					 unsigned char c)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	/* Wait while TX FIFO is full */
	while (uart->tx & TXDATA_FULL) {
	}

	uart->tx = (int)c;
}

/**
 * @brief Poll the device for input.
 *
 * @param dev UART device struct
 * @param c Pointer to character
 *
 * @return 0 if a character arrived, -1 if the input buffer if empty.
 */
static int uart_sifive_poll_in(struct device *dev, unsigned char *c)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);
	u32_t val = uart->rx;

	if (val & RXDATA_EMPTY) {
		return -1;
	}

	*c = (unsigned char)(val & RXDATA_MASK);

	return 0;
}

#ifdef CONFIG_UART_INTERRUPT_DRIVEN

/**
 * @brief Fill FIFO with data
 *
 * @param dev UART device struct
 * @param tx_data Data to transmit
 * @param size Number of bytes to send
 *
 * @return Number of bytes sent
 */
static int uart_sifive_fifo_fill(struct device *dev,
				const u8_t *tx_data,
				int size)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);
	int i;

	for (i = 0; i < size && !(uart->tx & TXDATA_FULL); i++)
		uart->tx = (int)tx_data[i];

	return i;
}

/**
 * @brief Read data from FIFO
 *
 * @param dev UART device struct
 * @param rxData Data container
 * @param size Container size
 *
 * @return Number of bytes read
 */
static int uart_sifive_fifo_read(struct device *dev,
				u8_t *rx_data,
				const int size)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);
	int i;
	u32_t val;

	for (i = 0; i < size; i++) {
		val = uart->rx;

		if (val & RXDATA_EMPTY)
			break;

		rx_data[i] = (u8_t)(val & RXDATA_MASK);
	}

	return i;
}

/**
 * @brief Enable TX interrupt in ie register
 *
 * @param dev UART device struct
 *
 * @return N/A
 */
static void uart_sifive_irq_tx_enable(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	uart->ie |= IE_TXWM;
}

/**
 * @brief Disable TX interrupt in ie register
 *
 * @param dev UART device struct
 *
 * @return N/A
 */
static void uart_sifive_irq_tx_disable(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	uart->ie &= ~IE_TXWM;
}

/**
 * @brief Check if Tx IRQ has been raised
 *
 * @param dev UART device struct
 *
 * @return 1 if an IRQ is ready, 0 otherwise
 */
static int uart_sifive_irq_tx_ready(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	return !!(uart->ip & IE_TXWM);
}

/**
 * @brief Check if nothing remains to be transmitted
 *
 * @param dev UART device struct
 *
 * @return 1 if nothing remains to be transmitted, 0 otherwise
 */
static int uart_sifive_irq_tx_complete(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	/*
	 * No TX EMPTY flag for this controller,
	 * just check if TX FIFO is not full
	 */
	return !(uart->tx & TXDATA_FULL);
}

/**
 * @brief Enable RX interrupt in ie register
 *
 * @param dev UART device struct
 *
 * @return N/A
 */
static void uart_sifive_irq_rx_enable(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	uart->ie |= IE_RXWM;
}

/**
 * @brief Disable RX interrupt in ie register
 *
 * @param dev UART device struct
 *
 * @return N/A
 */
static void uart_sifive_irq_rx_disable(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	uart->ie &= ~IE_RXWM;
}

/**
 * @brief Check if Rx IRQ has been raised
 *
 * @param dev UART device struct
 *
 * @return 1 if an IRQ is ready, 0 otherwise
 */
static int uart_sifive_irq_rx_ready(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	return !!(uart->ip & IE_RXWM);
}

/* No error interrupt for this controller */
static void uart_sifive_irq_err_enable(struct device *dev)
{
	ARG_UNUSED(dev);
}

static void uart_sifive_irq_err_disable(struct device *dev)
{
	ARG_UNUSED(dev);
}

/**
 * @brief Check if any IRQ is pending
 *
 * @param dev UART device struct
 *
 * @return 1 if an IRQ is pending, 0 otherwise
 */
static int uart_sifive_irq_is_pending(struct device *dev)
{
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	return !!(uart->ip & (IE_RXWM | IE_TXWM));
}

static int uart_sifive_irq_update(struct device *dev)
{
	return 1;
}

/**
 * @brief Set the callback function pointer for IRQ.
 *
 * @param dev UART device struct
 * @param cb Callback function pointer.
 *
 * @return N/A
 */
static void uart_sifive_irq_callback_set(struct device *dev,
					uart_irq_callback_user_data_t cb,
					void *cb_data)
{
	struct uart_sifive_data *data = DEV_DATA(dev);

	data->callback = cb;
	data->cb_data = cb_data;
}

static void uart_sifive_irq_handler(void *arg)
{
	struct device *dev = (struct device *)arg;
	struct uart_sifive_data *data = DEV_DATA(dev);

	if (data->callback)
		data->callback(data->cb_data);
}

#endif /* CONFIG_UART_INTERRUPT_DRIVEN */


static int uart_sifive_init(struct device *dev)
{
	const struct uart_sifive_device_config * const cfg = DEV_CFG(dev);
	volatile struct uart_sifive_regs_t *uart = DEV_UART(dev);

	/* Enable TX and RX channels */
	uart->txctrl = TXCTRL_TXEN | CTRL_CNT(cfg->txcnt_irq);
	uart->rxctrl = RXCTRL_RXEN | CTRL_CNT(cfg->rxcnt_irq);

	/* Set baud rate */
	uart->div = cfg->sys_clk_freq / cfg->baud_rate - 1;

#ifdef CONFIG_UART_INTERRUPT_DRIVEN
	/* Ensure that uart IRQ is disabled initially */
	uart->ie = 0U;

	/* Setup IRQ handler */
	cfg->cfg_func();
#endif

	return 0;
}

static const struct uart_driver_api uart_sifive_driver_api = {
	.poll_in          = uart_sifive_poll_in,
	.poll_out         = uart_sifive_poll_out,
	.err_check        = NULL,
#ifdef CONFIG_UART_INTERRUPT_DRIVEN
	.fifo_fill        = uart_sifive_fifo_fill,
	.fifo_read        = uart_sifive_fifo_read,
	.irq_tx_enable    = uart_sifive_irq_tx_enable,
	.irq_tx_disable   = uart_sifive_irq_tx_disable,
	.irq_tx_ready     = uart_sifive_irq_tx_ready,
	.irq_tx_complete  = uart_sifive_irq_tx_complete,
	.irq_rx_enable    = uart_sifive_irq_rx_enable,
	.irq_rx_disable   = uart_sifive_irq_rx_disable,
	.irq_rx_ready     = uart_sifive_irq_rx_ready,
	.irq_err_enable   = uart_sifive_irq_err_enable,
	.irq_err_disable  = uart_sifive_irq_err_disable,
	.irq_is_pending   = uart_sifive_irq_is_pending,
	.irq_update       = uart_sifive_irq_update,
	.irq_callback_set = uart_sifive_irq_callback_set,
#endif
};

#ifdef CONFIG_UART_SIFIVE_PORT_0

static struct uart_sifive_data uart_sifive_data_0;

#ifdef CONFIG_UART_INTERRUPT_DRIVEN
static void uart_sifive_irq_cfg_func_0(void);
#endif

static const struct uart_sifive_device_config uart_sifive_dev_cfg_0 = {
	.port         = DT_INST_0_SIFIVE_UART0_BASE_ADDRESS,
	.sys_clk_freq = DT_INST_0_SIFIVE_UART0_CLOCK_FREQUENCY,
	.baud_rate    = DT_INST_0_SIFIVE_UART0_CURRENT_SPEED,
	.rxcnt_irq    = CONFIG_UART_SIFIVE_PORT_0_RXCNT_IRQ,
	.txcnt_irq    = CONFIG_UART_SIFIVE_PORT_0_TXCNT_IRQ,
#ifdef CONFIG_UART_INTERRUPT_DRIVEN
	.cfg_func     = uart_sifive_irq_cfg_func_0,
#endif
};

DEVICE_AND_API_INIT(uart_sifive_0, DT_INST_0_SIFIVE_UART0_LABEL,
		    uart_sifive_init,
		    &uart_sifive_data_0, &uart_sifive_dev_cfg_0,
		    PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
		    (void *)&uart_sifive_driver_api);

#ifdef CONFIG_UART_INTERRUPT_DRIVEN
static void uart_sifive_irq_cfg_func_0(void)
{
	IRQ_CONNECT(DT_INST_0_SIFIVE_UART0_IRQ_0,
		    CONFIG_UART_SIFIVE_PORT_0_IRQ_PRIORITY,
		    uart_sifive_irq_handler, DEVICE_GET(uart_sifive_0),
		    0);

	irq_enable(DT_INST_0_SIFIVE_UART0_IRQ_0);
}
#endif

#endif /* CONFIG_UART_SIFIVE_PORT_0 */

#ifdef CONFIG_UART_SIFIVE_PORT_1

static struct uart_sifive_data uart_sifive_data_1;

#ifdef CONFIG_UART_INTERRUPT_DRIVEN
static void uart_sifive_irq_cfg_func_1(void);
#endif

static const struct uart_sifive_device_config uart_sifive_dev_cfg_1 = {
	.port         = DT_INST_1_SIFIVE_UART0_BASE_ADDRESS,
	.sys_clk_freq = DT_INST_1_SIFIVE_UART0_CLOCK_FREQUENCY,
	.baud_rate    = DT_INST_1_SIFIVE_UART0_CURRENT_SPEED,
	.rxcnt_irq    = CONFIG_UART_SIFIVE_PORT_1_RXCNT_IRQ,
	.txcnt_irq    = CONFIG_UART_SIFIVE_PORT_1_TXCNT_IRQ,
#ifdef CONFIG_UART_INTERRUPT_DRIVEN
	.cfg_func     = uart_sifive_irq_cfg_func_1,
#endif
};

DEVICE_AND_API_INIT(uart_sifive_1, DT_INST_1_SIFIVE_UART0_LABEL,
		    uart_sifive_init,
		    &uart_sifive_data_1, &uart_sifive_dev_cfg_1,
		    PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
		    (void *)&uart_sifive_driver_api);

#ifdef CONFIG_UART_INTERRUPT_DRIVEN
static void uart_sifive_irq_cfg_func_1(void)
{
	IRQ_CONNECT(DT_INST_1_SIFIVE_UART0_IRQ_0,
		    CONFIG_UART_SIFIVE_PORT_1_IRQ_PRIORITY,
		    uart_sifive_irq_handler, DEVICE_GET(uart_sifive_1),
		    0);

	irq_enable(DT_INST_1_SIFIVE_UART0_IRQ_0);
}
#endif

#endif /* CONFIG_UART_SIFIVE_PORT_1 */