// SPDX-License-Identifier: GPL-2.0
/*
 *  Driver for GRLIB serial ports (APBUART)
 *
 *  Based on linux/drivers/serial/amba.c
 *
 *  Copyright (C) 2000 Deep Blue Solutions Ltd.
 *  Copyright (C) 2003 Konrad Eisele <eiselekd@web.de>
 *  Copyright (C) 2006 Daniel Hellstrom <daniel@gaisler.com>, Aeroflex Gaisler AB
 *  Copyright (C) 2008 Gilead Kutnick <kutnickg@zin-tech.com>
 *  Copyright (C) 2009 Kristoffer Glembo <kristoffer@gaisler.com>, Aeroflex Gaisler AB
 */

#include <linux/module.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/serial.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/kthread.h>
#include <linux/device.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/serial_core.h>
#include <asm/irq.h>

#include "apbuart.h"

#define SERIAL_APBUART_MAJOR    TTY_MAJOR
#define SERIAL_APBUART_MINOR    64
#define UART_DUMMY_RSR_RX       0x8000  /* for ignore all read */

static void apbuart_tx_chars(struct uart_port *port);

static void apbuart_stop_tx(struct uart_port *port)
{
        unsigned int cr;

        cr = UART_GET_CTRL(port);
        cr &= ~UART_CTRL_TI;
        UART_PUT_CTRL(port, cr);
}

static void apbuart_start_tx(struct uart_port *port)
{
        unsigned int cr;

        cr = UART_GET_CTRL(port);
        cr |= UART_CTRL_TI;
        UART_PUT_CTRL(port, cr);

        if (UART_GET_STATUS(port) & UART_STATUS_THE)
                apbuart_tx_chars(port);
}

static void apbuart_stop_rx(struct uart_port *port)
{
        unsigned int cr;

        cr = UART_GET_CTRL(port);
        cr &= ~(UART_CTRL_RI);
        UART_PUT_CTRL(port, cr);
}

static void apbuart_rx_chars(struct uart_port *port)
{
        unsigned int status, rsr;
        unsigned int max_chars = port->fifosize;
        u8 ch, flag;

        status = UART_GET_STATUS(port);

        while (UART_RX_DATA(status) && (max_chars--)) {

                ch = UART_GET_CHAR(port);
                flag = TTY_NORMAL;

                port->icount.rx++;

                rsr = UART_GET_STATUS(port) | UART_DUMMY_RSR_RX;
                UART_PUT_STATUS(port, 0);
                if (rsr & UART_STATUS_ERR) {

                        if (rsr & UART_STATUS_BR) {
                                rsr &= ~(UART_STATUS_FE | UART_STATUS_PE);
                                port->icount.brk++;
                                if (uart_handle_break(port))
                                        goto ignore_char;
                        } else if (rsr & UART_STATUS_PE) {
                                port->icount.parity++;
                        } else if (rsr & UART_STATUS_FE) {
                                port->icount.frame++;
                        }
                        if (rsr & UART_STATUS_OE)
                                port->icount.overrun++;

                        rsr &= port->read_status_mask;

                        if (rsr & UART_STATUS_PE)
                                flag = TTY_PARITY;
                        else if (rsr & UART_STATUS_FE)
                                flag = TTY_FRAME;
                }

                if (uart_handle_sysrq_char(port, ch))
                        goto ignore_char;

                uart_insert_char(port, rsr, UART_STATUS_OE, ch, flag);


              ignore_char:
                status = UART_GET_STATUS(port);
        }

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

static void apbuart_tx_chars(struct uart_port *port)
{
        u8 ch;

        uart_port_tx_limited(port, ch, port->fifosize,
                true,
                UART_PUT_CHAR(port, ch),
                ({}));
}

static irqreturn_t apbuart_int(int irq, void *dev_id)
{
        struct uart_port *port = dev_id;
        unsigned int status;

        uart_port_lock(port);

        status = UART_GET_STATUS(port);
        if (status & UART_STATUS_DR)
                apbuart_rx_chars(port);
        if (status & UART_STATUS_THE)
                apbuart_tx_chars(port);

        uart_port_unlock(port);

        return IRQ_HANDLED;
}

static unsigned int apbuart_tx_empty(struct uart_port *port)
{
        unsigned int status = UART_GET_STATUS(port);
        return status & UART_STATUS_THE ? TIOCSER_TEMT : 0;
}

static unsigned int apbuart_get_mctrl(struct uart_port *port)
{
        /* The GRLIB APBUART handles flow control in hardware */
        return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
}

static void apbuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        /* The GRLIB APBUART handles flow control in hardware */
}

static void apbuart_break_ctl(struct uart_port *port, int break_state)
{
        /* We don't support sending break */
}

static int apbuart_startup(struct uart_port *port)
{
        int retval;
        unsigned int cr;

        /* Allocate the IRQ */
        retval = request_irq(port->irq, apbuart_int, 0, "apbuart", port);
        if (retval)
                return retval;

        /* Finally, enable interrupts */
        cr = UART_GET_CTRL(port);
        UART_PUT_CTRL(port,
                      cr | UART_CTRL_RE | UART_CTRL_TE |
                      UART_CTRL_RI | UART_CTRL_TI);

        return 0;
}

static void apbuart_shutdown(struct uart_port *port)
{
        unsigned int cr;

        /* disable all interrupts, disable the port */
        cr = UART_GET_CTRL(port);
        UART_PUT_CTRL(port,
                      cr & ~(UART_CTRL_RE | UART_CTRL_TE |
                             UART_CTRL_RI | UART_CTRL_TI));

        /* Free the interrupt */
        free_irq(port->irq, port);
}

static void apbuart_set_termios(struct uart_port *port,
                                struct ktermios *termios, const struct ktermios *old)
{
        unsigned int cr;
        unsigned long flags;
        unsigned int baud, quot;

        /* Ask the core to calculate the divisor for us. */
        baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);

        /* uart_get_divisor calc a *16 uart freq, apbuart is *8 */
        quot = (uart_get_divisor(port, baud)) * 2;
        cr = UART_GET_CTRL(port);
        cr &= ~(UART_CTRL_PE | UART_CTRL_PS);

        if (termios->c_cflag & PARENB) {
                cr |= UART_CTRL_PE;
                if ((termios->c_cflag & PARODD))
                        cr |= UART_CTRL_PS;
        }

        /* Enable flow control. */
        if (termios->c_cflag & CRTSCTS)
                cr |= UART_CTRL_FL;

        uart_port_lock_irqsave(port, &flags);

        /* Update the per-port timeout. */
        uart_update_timeout(port, termios->c_cflag, baud);

        port->read_status_mask = UART_STATUS_OE;
        if (termios->c_iflag & INPCK)
                port->read_status_mask |= UART_STATUS_FE | UART_STATUS_PE;

        /* Characters to ignore */
        port->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                port->ignore_status_mask |= UART_STATUS_FE | UART_STATUS_PE;

        /* Ignore all characters if CREAD is not set. */
        if ((termios->c_cflag & CREAD) == 0)
                port->ignore_status_mask |= UART_DUMMY_RSR_RX;

        /* Set baud rate */
        quot -= 1;
        UART_PUT_SCAL(port, quot);
        UART_PUT_CTRL(port, cr);

        uart_port_unlock_irqrestore(port, flags);
}

static const char *apbuart_type(struct uart_port *port)
{
        return port->type == PORT_APBUART ? "GRLIB/APBUART" : NULL;
}

static void apbuart_release_port(struct uart_port *port)
{
        release_mem_region(port->mapbase, 0x100);
}

static int apbuart_request_port(struct uart_port *port)
{
        return request_mem_region(port->mapbase, 0x100, "grlib-apbuart")
            != NULL ? 0 : -EBUSY;
        return 0;
}

/* Configure/autoconfigure the port */
static void apbuart_config_port(struct uart_port *port, int flags)
{
        if (flags & UART_CONFIG_TYPE) {
                port->type = PORT_APBUART;
                apbuart_request_port(port);
        }
}

/* Verify the new serial_struct (for TIOCSSERIAL) */
static int apbuart_verify_port(struct uart_port *port,
                               struct serial_struct *ser)
{
        int ret = 0;
        if (ser->type != PORT_UNKNOWN && ser->type != PORT_APBUART)
                ret = -EINVAL;
        if (ser->irq < 0 || ser->irq >= NR_IRQS)
                ret = -EINVAL;
        if (ser->baud_base < 9600)
                ret = -EINVAL;
        return ret;
}

static const struct uart_ops grlib_apbuart_ops = {
        .tx_empty = apbuart_tx_empty,
        .set_mctrl = apbuart_set_mctrl,
        .get_mctrl = apbuart_get_mctrl,
        .stop_tx = apbuart_stop_tx,
        .start_tx = apbuart_start_tx,
        .stop_rx = apbuart_stop_rx,
        .break_ctl = apbuart_break_ctl,
        .startup = apbuart_startup,
        .shutdown = apbuart_shutdown,
        .set_termios = apbuart_set_termios,
        .type = apbuart_type,
        .release_port = apbuart_release_port,
        .request_port = apbuart_request_port,
        .config_port = apbuart_config_port,
        .verify_port = apbuart_verify_port,
};

static struct uart_port grlib_apbuart_ports[UART_NR];
static struct device_node *grlib_apbuart_nodes[UART_NR];

static int apbuart_scan_fifo_size(struct uart_port *port, int portnumber)
{
        int ctrl, loop = 0;
        int status;
        int fifosize;
        unsigned long flags;

        ctrl = UART_GET_CTRL(port);

        /*
         * Enable the transceiver and wait for it to be ready to send data.
         * Clear interrupts so that this process will not be externally
         * interrupted in the middle (which can cause the transceiver to
         * drain prematurely).
         */

        local_irq_save(flags);

        UART_PUT_CTRL(port, ctrl | UART_CTRL_TE);

        while (!UART_TX_READY(UART_GET_STATUS(port)))
                loop++;

        /*
         * Disable the transceiver so data isn't actually sent during the
         * actual test.
         */

        UART_PUT_CTRL(port, ctrl & ~(UART_CTRL_TE));

        fifosize = 1;
        UART_PUT_CHAR(port, 0);

        /*
         * So long as transmitting a character increments the tranceivier FIFO
         * length the FIFO must be at least that big. These bytes will
         * automatically drain off of the FIFO.
         */

        status = UART_GET_STATUS(port);
        while (((status >> 20) & 0x3F) == fifosize) {
                fifosize++;
                UART_PUT_CHAR(port, 0);
                status = UART_GET_STATUS(port);
        }

        fifosize--;

        UART_PUT_CTRL(port, ctrl);
        local_irq_restore(flags);

        if (fifosize == 0)
                fifosize = 1;

        return fifosize;
}

static void apbuart_flush_fifo(struct uart_port *port)
{
        int i;

        for (i = 0; i < port->fifosize; i++)
                UART_GET_CHAR(port);
}


/* ======================================================================== */
/* Console driver, if enabled                                               */
/* ======================================================================== */

#ifdef CONFIG_SERIAL_GRLIB_GAISLER_APBUART_CONSOLE

static void apbuart_console_putchar(struct uart_port *port, unsigned char ch)
{
        unsigned int status;
        do {
                status = UART_GET_STATUS(port);
        } while (!UART_TX_READY(status));
        UART_PUT_CHAR(port, ch);
}

static void
apbuart_console_write(struct console *co, const char *s, unsigned int count)
{
        struct uart_port *port = &grlib_apbuart_ports[co->index];
        unsigned int status, old_cr, new_cr;

        /* First save the CR then disable the interrupts */
        old_cr = UART_GET_CTRL(port);
        new_cr = old_cr & ~(UART_CTRL_RI | UART_CTRL_TI);
        UART_PUT_CTRL(port, new_cr);

        uart_console_write(port, s, count, apbuart_console_putchar);

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore the TCR
         */
        do {
                status = UART_GET_STATUS(port);
        } while (!UART_TX_READY(status));
        UART_PUT_CTRL(port, old_cr);
}

static void __init
apbuart_console_get_options(struct uart_port *port, int *baud,
                            int *parity, int *bits)
{
        if (UART_GET_CTRL(port) & (UART_CTRL_RE | UART_CTRL_TE)) {

                unsigned int quot, status;
                status = UART_GET_STATUS(port);

                *parity = 'n';
                if (status & UART_CTRL_PE) {
                        if ((status & UART_CTRL_PS) == 0)
                                *parity = 'e';
                        else
                                *parity = 'o';
                }

                *bits = 8;
                quot = UART_GET_SCAL(port) / 8;
                *baud = port->uartclk / (16 * (quot + 1));
        }
}

static int __init apbuart_console_setup(struct console *co, char *options)
{
        struct uart_port *port;
        int baud = 38400;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';

        pr_debug("apbuart_console_setup co=%p, co->index=%i, options=%s\n",
                 co, co->index, options);

        /*
         * Check whether an invalid uart number has been specified, and
         * if so, search for the first available port that does have
         * console support.
         */
        if (co->index >= grlib_apbuart_port_nr)
                co->index = 0;

        port = &grlib_apbuart_ports[co->index];

        spin_lock_init(&port->lock);

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);
        else
                apbuart_console_get_options(port, &baud, &parity, &bits);

        return uart_set_options(port, co, baud, parity, bits, flow);
}

static struct uart_driver grlib_apbuart_driver;

static struct console grlib_apbuart_console = {
        .name = "ttyS",
        .write = apbuart_console_write,
        .device = uart_console_device,
        .setup = apbuart_console_setup,
        .flags = CON_PRINTBUFFER,
        .index = -1,
        .data = &grlib_apbuart_driver,
};


static int grlib_apbuart_configure(void);

static int __init apbuart_console_init(void)
{
        if (grlib_apbuart_configure())
                return -ENODEV;
        register_console(&grlib_apbuart_console);
        return 0;
}

console_initcall(apbuart_console_init);

#define APBUART_CONSOLE (&grlib_apbuart_console)
#else
#define APBUART_CONSOLE NULL
#endif

static struct uart_driver grlib_apbuart_driver = {
        .owner = THIS_MODULE,
        .driver_name = "serial_apbuart",
        .dev_name = "ttyS",
        .major = SERIAL_APBUART_MAJOR,
        .minor = SERIAL_APBUART_MINOR,
        .nr = UART_NR,
        .cons = APBUART_CONSOLE,
};


/* ======================================================================== */
/* OF Platform Driver                                                       */
/* ======================================================================== */

static int apbuart_probe(struct platform_device *op)
{
        int i;
        struct uart_port *port = NULL;

        for (i = 0; i < grlib_apbuart_port_nr; i++) {
                if (op->dev.of_node == grlib_apbuart_nodes[i])
                        break;
        }

        port = &grlib_apbuart_ports[i];
        port->dev = &op->dev;
        port->irq = op->archdata.irqs[0];

        uart_add_one_port(&grlib_apbuart_driver, (struct uart_port *) port);

        apbuart_flush_fifo((struct uart_port *) port);

        printk(KERN_INFO "grlib-apbuart at 0x%llx, irq %d\n",
               (unsigned long long) port->mapbase, port->irq);
        return 0;
}

static const struct of_device_id apbuart_match[] = {
        {
         .name = "GAISLER_APBUART",
         },
        {
         .name = "01_00c",
         },
        {},
};
MODULE_DEVICE_TABLE(of, apbuart_match);

static struct platform_driver grlib_apbuart_of_driver = {
        .probe = apbuart_probe,
        .driver = {
                .name = "grlib-apbuart",
                .of_match_table = apbuart_match,
        },
};


static int __init grlib_apbuart_configure(void)
{
        struct device_node *np;
        int line = 0;

        for_each_matching_node(np, apbuart_match) {
                const int *ampopts;
                const u32 *freq_hz;
                const struct amba_prom_registers *regs;
                struct uart_port *port;
                unsigned long addr;

                ampopts = of_get_property(np, "ampopts", NULL);
                if (ampopts && (*ampopts == 0))
                        continue; /* Ignore if used by another OS instance */
                regs = of_get_property(np, "reg", NULL);
                /* Frequency of APB Bus is frequency of UART */
                freq_hz = of_get_property(np, "freq", NULL);

                if (!regs || !freq_hz || (*freq_hz == 0))
                        continue;

                grlib_apbuart_nodes[line] = np;

                addr = regs->phys_addr;

                port = &grlib_apbuart_ports[line];

                port->mapbase = addr;
                port->membase = ioremap(addr, sizeof(struct grlib_apbuart_regs_map));
                port->irq = 0;
                port->iotype = UPIO_MEM;
                port->ops = &grlib_apbuart_ops;
                port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_GRLIB_GAISLER_APBUART_CONSOLE);
                port->flags = UPF_BOOT_AUTOCONF;
                port->line = line;
                port->uartclk = *freq_hz;
                port->fifosize = apbuart_scan_fifo_size((struct uart_port *) port, line);
                line++;

                /* We support maximum UART_NR uarts ... */
                if (line == UART_NR)
                        break;
        }

        grlib_apbuart_driver.nr = grlib_apbuart_port_nr = line;
        return line ? 0 : -ENODEV;
}

static int __init grlib_apbuart_init(void)
{
        int ret;

        /* Find all APBUARTS in device the tree and initialize their ports */
        ret = grlib_apbuart_configure();
        if (ret)
                return ret;

        printk(KERN_INFO "Serial: GRLIB APBUART driver\n");

        ret = uart_register_driver(&grlib_apbuart_driver);

        if (ret) {
                printk(KERN_ERR "%s: uart_register_driver failed (%i)\n",
                       __FILE__, ret);
                return ret;
        }

        ret = platform_driver_register(&grlib_apbuart_of_driver);
        if (ret) {
                printk(KERN_ERR
                       "%s: platform_driver_register failed (%i)\n",
                       __FILE__, ret);
                uart_unregister_driver(&grlib_apbuart_driver);
                return ret;
        }

        return ret;
}

static void __exit grlib_apbuart_exit(void)
{
        int i;

        for (i = 0; i < grlib_apbuart_port_nr; i++)
                uart_remove_one_port(&grlib_apbuart_driver,
                                     &grlib_apbuart_ports[i]);

        uart_unregister_driver(&grlib_apbuart_driver);
        platform_driver_unregister(&grlib_apbuart_of_driver);
}

module_init(grlib_apbuart_init);
module_exit(grlib_apbuart_exit);

MODULE_AUTHOR("Aeroflex Gaisler AB");
MODULE_DESCRIPTION("GRLIB APBUART serial driver");
MODULE_VERSION("2.1");
MODULE_LICENSE("GPL");