// SPDX-License-Identifier: GPL-2.0+
/*
 * altera_jtaguart.c -- Altera JTAG UART driver
 *
 * Based on mcf.c -- Freescale ColdFire UART driver
 *
 * (C) Copyright 2003-2007, Greg Ungerer <gerg@snapgear.com>
 * (C) Copyright 2008, Thomas Chou <thomas@wytron.com.tw>
 * (C) Copyright 2010, Tobias Klauser <tklauser@distanz.ch>
 */

#include <linux/bitfield.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/console.h>
#include <linux/of.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/altera_jtaguart.h>

/*
 * Altera JTAG UART register definitions according to the Altera JTAG UART
 * datasheet: https://www.altera.com/literature/hb/nios2/n2cpu_nii51009.pdf
 */

#define ALTERA_JTAGUART_SIZE                    8

#define ALTERA_JTAGUART_DATA_REG                0

#define ALTERA_JTAGUART_DATA_DATA_MSK           0x000000FF
#define ALTERA_JTAGUART_DATA_RVALID_MSK         0x00008000
#define ALTERA_JTAGUART_DATA_RAVAIL_MSK         0xFFFF0000
#define ALTERA_JTAGUART_DATA_RAVAIL_OFF         16

#define ALTERA_JTAGUART_CONTROL_REG             4

#define ALTERA_JTAGUART_CONTROL_RE_MSK          0x00000001
#define ALTERA_JTAGUART_CONTROL_WE_MSK          0x00000002
#define ALTERA_JTAGUART_CONTROL_RI_MSK          0x00000100
#define ALTERA_JTAGUART_CONTROL_RI_OFF          8
#define ALTERA_JTAGUART_CONTROL_WI_MSK          0x00000200
#define ALTERA_JTAGUART_CONTROL_AC_MSK          0x00000400
#define ALTERA_JTAGUART_CONTROL_WSPACE_MSK      0xFFFF0000

static unsigned int altera_jtaguart_tx_space(struct uart_port *port, u32 *ctlp)
{
        u32 ctl = readl(port->membase + ALTERA_JTAGUART_CONTROL_REG);

        if (ctlp)
                *ctlp = ctl;

        return FIELD_GET(ALTERA_JTAGUART_CONTROL_WSPACE_MSK, ctl);
}

static unsigned int altera_jtaguart_tx_empty(struct uart_port *port)
{
        return altera_jtaguart_tx_space(port, NULL) ? TIOCSER_TEMT : 0;
}

static unsigned int altera_jtaguart_get_mctrl(struct uart_port *port)
{
        return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
}

static void altera_jtaguart_set_mctrl(struct uart_port *port, unsigned int sigs)
{
}

static void altera_jtaguart_start_tx(struct uart_port *port)
{
        port->read_status_mask |= ALTERA_JTAGUART_CONTROL_WE_MSK;
        writel(port->read_status_mask,
                        port->membase + ALTERA_JTAGUART_CONTROL_REG);
}

static void altera_jtaguart_stop_tx(struct uart_port *port)
{
        port->read_status_mask &= ~ALTERA_JTAGUART_CONTROL_WE_MSK;
        writel(port->read_status_mask,
                        port->membase + ALTERA_JTAGUART_CONTROL_REG);
}

static void altera_jtaguart_stop_rx(struct uart_port *port)
{
        port->read_status_mask &= ~ALTERA_JTAGUART_CONTROL_RE_MSK;
        writel(port->read_status_mask,
                        port->membase + ALTERA_JTAGUART_CONTROL_REG);
}

static void altera_jtaguart_break_ctl(struct uart_port *port, int break_state)
{
}

static void altera_jtaguart_set_termios(struct uart_port *port,
                                        struct ktermios *termios,
                                        const struct ktermios *old)
{
        /* Just copy the old termios settings back */
        if (old)
                tty_termios_copy_hw(termios, old);
}

static void altera_jtaguart_rx_chars(struct uart_port *port)
{
        u32 status;
        u8 ch;

        while ((status = readl(port->membase + ALTERA_JTAGUART_DATA_REG)) &
               ALTERA_JTAGUART_DATA_RVALID_MSK) {
                ch = status & ALTERA_JTAGUART_DATA_DATA_MSK;
                port->icount.rx++;

                if (uart_handle_sysrq_char(port, ch))
                        continue;
                uart_insert_char(port, 0, 0, ch, TTY_NORMAL);
        }

        tty_flip_buffer_push(&port->state->port);
}

static void altera_jtaguart_tx_chars(struct uart_port *port)
{
        unsigned int count;
        u8 ch;

        count = altera_jtaguart_tx_space(port, NULL);

        uart_port_tx_limited(port, ch, count,
                true,
                writel(ch, port->membase + ALTERA_JTAGUART_DATA_REG),
                ({}));
}

static irqreturn_t altera_jtaguart_interrupt(int irq, void *data)
{
        struct uart_port *port = data;
        unsigned int isr;

        isr = (readl(port->membase + ALTERA_JTAGUART_CONTROL_REG) >>
               ALTERA_JTAGUART_CONTROL_RI_OFF) & port->read_status_mask;

        uart_port_lock(port);

        if (isr & ALTERA_JTAGUART_CONTROL_RE_MSK)
                altera_jtaguart_rx_chars(port);
        if (isr & ALTERA_JTAGUART_CONTROL_WE_MSK)
                altera_jtaguart_tx_chars(port);

        uart_port_unlock(port);

        return IRQ_RETVAL(isr);
}

static void altera_jtaguart_config_port(struct uart_port *port, int flags)
{
        port->type = PORT_ALTERA_JTAGUART;

        /* Clear mask, so no surprise interrupts. */
        writel(0, port->membase + ALTERA_JTAGUART_CONTROL_REG);
}

static int altera_jtaguart_startup(struct uart_port *port)
{
        unsigned long flags;
        int ret;

        ret = request_irq(port->irq, altera_jtaguart_interrupt, 0,
                        dev_name(port->dev), port);
        if (ret) {
                dev_err(port->dev, "unable to attach Altera JTAG UART %d interrupt vector=%d\n",
                        port->line, port->irq);
                return ret;
        }

        uart_port_lock_irqsave(port, &flags);

        /* Enable RX interrupts now */
        port->read_status_mask = ALTERA_JTAGUART_CONTROL_RE_MSK;
        writel(port->read_status_mask,
                        port->membase + ALTERA_JTAGUART_CONTROL_REG);

        uart_port_unlock_irqrestore(port, flags);

        return 0;
}

static void altera_jtaguart_shutdown(struct uart_port *port)
{
        unsigned long flags;

        uart_port_lock_irqsave(port, &flags);

        /* Disable all interrupts now */
        port->read_status_mask = 0;
        writel(port->read_status_mask,
                        port->membase + ALTERA_JTAGUART_CONTROL_REG);

        uart_port_unlock_irqrestore(port, flags);

        free_irq(port->irq, port);
}

static const char *altera_jtaguart_type(struct uart_port *port)
{
        return (port->type == PORT_ALTERA_JTAGUART) ? "Altera JTAG UART" : NULL;
}

static int altera_jtaguart_request_port(struct uart_port *port)
{
        /* UARTs always present */
        return 0;
}

static void altera_jtaguart_release_port(struct uart_port *port)
{
        /* Nothing to release... */
}

static int altera_jtaguart_verify_port(struct uart_port *port,
                                       struct serial_struct *ser)
{
        if (ser->type != PORT_UNKNOWN && ser->type != PORT_ALTERA_JTAGUART)
                return -EINVAL;
        return 0;
}

/*
 *      Define the basic serial functions we support.
 */
static const struct uart_ops altera_jtaguart_ops = {
        .tx_empty       = altera_jtaguart_tx_empty,
        .get_mctrl      = altera_jtaguart_get_mctrl,
        .set_mctrl      = altera_jtaguart_set_mctrl,
        .start_tx       = altera_jtaguart_start_tx,
        .stop_tx        = altera_jtaguart_stop_tx,
        .stop_rx        = altera_jtaguart_stop_rx,
        .break_ctl      = altera_jtaguart_break_ctl,
        .startup        = altera_jtaguart_startup,
        .shutdown       = altera_jtaguart_shutdown,
        .set_termios    = altera_jtaguart_set_termios,
        .type           = altera_jtaguart_type,
        .request_port   = altera_jtaguart_request_port,
        .release_port   = altera_jtaguart_release_port,
        .config_port    = altera_jtaguart_config_port,
        .verify_port    = altera_jtaguart_verify_port,
};

#define ALTERA_JTAGUART_MAXPORTS 1
static struct uart_port altera_jtaguart_ports[ALTERA_JTAGUART_MAXPORTS];

#if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE)

#if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE_BYPASS)
static void altera_jtaguart_console_putc(struct uart_port *port, unsigned char c)
{
        unsigned long flags;
        u32 status;

        uart_port_lock_irqsave(port, &flags);
        while (!altera_jtaguart_tx_space(port, &status)) {
                uart_port_unlock_irqrestore(port, flags);

                if ((status & ALTERA_JTAGUART_CONTROL_AC_MSK) == 0) {
                        return; /* no connection activity */
                }

                cpu_relax();
                uart_port_lock_irqsave(port, &flags);
        }
        writel(c, port->membase + ALTERA_JTAGUART_DATA_REG);
        uart_port_unlock_irqrestore(port, flags);
}
#else
static void altera_jtaguart_console_putc(struct uart_port *port, unsigned char c)
{
        unsigned long flags;

        uart_port_lock_irqsave(port, &flags);
        while (!altera_jtaguart_tx_space(port, NULL)) {
                uart_port_unlock_irqrestore(port, flags);
                cpu_relax();
                uart_port_lock_irqsave(port, &flags);
        }
        writel(c, port->membase + ALTERA_JTAGUART_DATA_REG);
        uart_port_unlock_irqrestore(port, flags);
}
#endif

static void altera_jtaguart_console_write(struct console *co, const char *s,
                                          unsigned int count)
{
        struct uart_port *port = &altera_jtaguart_ports[co->index];

        uart_console_write(port, s, count, altera_jtaguart_console_putc);
}

static int __init altera_jtaguart_console_setup(struct console *co,
                                                char *options)
{
        struct uart_port *port;

        if (co->index < 0 || co->index >= ALTERA_JTAGUART_MAXPORTS)
                return -EINVAL;
        port = &altera_jtaguart_ports[co->index];
        if (port->membase == NULL)
                return -ENODEV;
        return 0;
}

static struct uart_driver altera_jtaguart_driver;

static struct console altera_jtaguart_console = {
        .name   = "ttyJ",
        .write  = altera_jtaguart_console_write,
        .device = uart_console_device,
        .setup  = altera_jtaguart_console_setup,
        .flags  = CON_PRINTBUFFER,
        .index  = -1,
        .data   = &altera_jtaguart_driver,
};

static int __init altera_jtaguart_console_init(void)
{
        register_console(&altera_jtaguart_console);
        return 0;
}

console_initcall(altera_jtaguart_console_init);

#define ALTERA_JTAGUART_CONSOLE (&altera_jtaguart_console)

static void altera_jtaguart_earlycon_write(struct console *co, const char *s,
                                           unsigned int count)
{
        struct earlycon_device *dev = co->data;

        uart_console_write(&dev->port, s, count, altera_jtaguart_console_putc);
}

static int __init altera_jtaguart_earlycon_setup(struct earlycon_device *dev,
                                                 const char *options)
{
        if (!dev->port.membase)
                return -ENODEV;

        dev->con->write = altera_jtaguart_earlycon_write;
        return 0;
}

OF_EARLYCON_DECLARE(juart, "altr,juart-1.0", altera_jtaguart_earlycon_setup);

#else

#define ALTERA_JTAGUART_CONSOLE NULL

#endif /* CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE */

static struct uart_driver altera_jtaguart_driver = {
        .owner          = THIS_MODULE,
        .driver_name    = KBUILD_MODNAME,
        .dev_name       = "ttyJ",
        .major          = ALTERA_JTAGUART_MAJOR,
        .minor          = ALTERA_JTAGUART_MINOR,
        .nr             = ALTERA_JTAGUART_MAXPORTS,
        .cons           = ALTERA_JTAGUART_CONSOLE,
};

static int altera_jtaguart_probe(struct platform_device *pdev)
{
        struct altera_jtaguart_platform_uart *platp =
                        dev_get_platdata(&pdev->dev);
        struct uart_port *port;
        struct resource *res_mem;
        int i = pdev->id;
        int irq;

        /* -1 emphasizes that the platform must have one port, no .N suffix */
        if (i == -1)
                i = 0;

        if (i >= ALTERA_JTAGUART_MAXPORTS)
                return -EINVAL;

        port = &altera_jtaguart_ports[i];

        res_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (res_mem)
                port->mapbase = res_mem->start;
        else if (platp)
                port->mapbase = platp->mapbase;
        else
                return -ENODEV;

        irq = platform_get_irq_optional(pdev, 0);
        if (irq < 0 && irq != -ENXIO)
                return irq;
        if (irq > 0)
                port->irq = irq;
        else if (platp)
                port->irq = platp->irq;
        else
                return -ENODEV;

        port->membase = ioremap(port->mapbase, ALTERA_JTAGUART_SIZE);
        if (!port->membase)
                return -ENOMEM;

        port->line = i;
        port->type = PORT_ALTERA_JTAGUART;
        port->iotype = SERIAL_IO_MEM;
        port->ops = &altera_jtaguart_ops;
        port->flags = UPF_BOOT_AUTOCONF;
        port->dev = &pdev->dev;

        uart_add_one_port(&altera_jtaguart_driver, port);

        return 0;
}

static void altera_jtaguart_remove(struct platform_device *pdev)
{
        struct uart_port *port;
        int i = pdev->id;

        if (i == -1)
                i = 0;

        port = &altera_jtaguart_ports[i];
        uart_remove_one_port(&altera_jtaguart_driver, port);
        iounmap(port->membase);
}

#ifdef CONFIG_OF
static const struct of_device_id altera_jtaguart_match[] = {
        { .compatible = "ALTR,juart-1.0", },
        { .compatible = "altr,juart-1.0", },
        {},
};
MODULE_DEVICE_TABLE(of, altera_jtaguart_match);
#endif /* CONFIG_OF */

static struct platform_driver altera_jtaguart_platform_driver = {
        .probe  = altera_jtaguart_probe,
        .remove = altera_jtaguart_remove,
        .driver = {
                .name           = KBUILD_MODNAME,
                .of_match_table = of_match_ptr(altera_jtaguart_match),
        },
};

static int __init altera_jtaguart_init(void)
{
        int rc;

        rc = uart_register_driver(&altera_jtaguart_driver);
        if (rc)
                return rc;
        rc = platform_driver_register(&altera_jtaguart_platform_driver);
        if (rc)
                uart_unregister_driver(&altera_jtaguart_driver);
        return rc;
}

static void __exit altera_jtaguart_exit(void)
{
        platform_driver_unregister(&altera_jtaguart_platform_driver);
        uart_unregister_driver(&altera_jtaguart_driver);
}

module_init(altera_jtaguart_init);
module_exit(altera_jtaguart_exit);

MODULE_DESCRIPTION("Altera JTAG UART driver");
MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" KBUILD_MODNAME);