// SPDX-License-Identifier: GPL-2.0
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/mcb.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/serial_8250.h>

#define MEN_UART_ID_Z025 0x19
#define MEN_UART_ID_Z057 0x39
#define MEN_UART_ID_Z125 0x7d

/*
 * IP Cores Z025 and Z057 can have up to 4 UART
 * The UARTs available are stored in a global
 * register saved in physical address + 0x40
 * Is saved as follows:
 *
 * 7                                                              0
 * +------+-------+-------+-------+-------+-------+-------+-------+
 * |UART4 | UART3 | UART2 | UART1 | U4irq | U3irq | U2irq | U1irq |
 * +------+-------+-------+-------+-------+-------+-------+-------+
 */
#define MEN_UART1_MASK  0x01
#define MEN_UART2_MASK  0x02
#define MEN_UART3_MASK  0x04
#define MEN_UART4_MASK  0x08

#define MEN_Z025_MAX_UARTS              4
#define MEN_UART_MEM_SIZE               0x10
#define MEM_UART_REGISTER_SIZE          0x01
#define MEN_Z025_REGISTER_OFFSET        0x40

#define MEN_UART1_OFFSET        0
#define MEN_UART2_OFFSET        (MEN_UART1_OFFSET + MEN_UART_MEM_SIZE)
#define MEN_UART3_OFFSET        (MEN_UART2_OFFSET + MEN_UART_MEM_SIZE)
#define MEN_UART4_OFFSET        (MEN_UART3_OFFSET + MEN_UART_MEM_SIZE)

#define MEN_READ_REGISTER(addr) readb(addr)

struct serial_8250_men_mcb_data {
        int num_ports;
        int line[MEN_Z025_MAX_UARTS];
        unsigned int offset[MEN_Z025_MAX_UARTS];
};

/*
 * The Z125 16550-compatible UART has no fixed base clock assigned
 * So, depending on the board we're on, we need to adjust the
 * parameter in order to really set the correct baudrate, and
 * do so if possible without user interaction
 */
static u32 men_lookup_uartclk(struct mcb_device *mdev)
{
        /* use default value if board is not available below */
        u32 clkval = 1041666;

        dev_info(&mdev->dev, "%s on board %s\n",
                dev_name(&mdev->dev),
                mdev->bus->name);
        if  (strncmp(mdev->bus->name, "F075", 4) == 0)
                clkval = 1041666;
        else if (strncmp(mdev->bus->name, "F216", 4) == 0)
                clkval = 1843200;
        else if (strncmp(mdev->bus->name, "F210", 4) == 0)
                clkval = 115200;
        else if (strstr(mdev->bus->name, "215"))
                clkval = 1843200;
        else
                dev_info(&mdev->dev,
                         "board not detected, using default uartclk\n");

        clkval = clkval  << 4;

        return clkval;
}

static int read_uarts_available_from_register(struct resource *mem_res,
                                              u8 *uarts_available)
{
        void __iomem *mem;
        int reg_value;

        if (!request_mem_region(mem_res->start + MEN_Z025_REGISTER_OFFSET,
                                MEM_UART_REGISTER_SIZE,  KBUILD_MODNAME)) {
                return -EBUSY;
        }

        mem = ioremap(mem_res->start + MEN_Z025_REGISTER_OFFSET,
                      MEM_UART_REGISTER_SIZE);
        if (!mem) {
                release_mem_region(mem_res->start + MEN_Z025_REGISTER_OFFSET,
                                   MEM_UART_REGISTER_SIZE);
                return -ENOMEM;
        }

        reg_value = MEN_READ_REGISTER(mem);

        iounmap(mem);

        release_mem_region(mem_res->start + MEN_Z025_REGISTER_OFFSET,
                           MEM_UART_REGISTER_SIZE);

        *uarts_available = reg_value >> 4;

        return 0;
}

static int read_serial_data(struct mcb_device *mdev,
                            struct resource *mem_res,
                            struct serial_8250_men_mcb_data *serial_data)
{
        u8 uarts_available;
        int count = 0;
        int mask;
        int res;
        int i;

        res = read_uarts_available_from_register(mem_res, &uarts_available);
        if (res < 0)
                return res;

        for (i = 0; i < MEN_Z025_MAX_UARTS; i++) {
                mask = 0x1 << i;
                switch (uarts_available & mask) {
                case MEN_UART1_MASK:
                        serial_data->offset[count] = MEN_UART1_OFFSET;
                        count++;
                        break;
                case MEN_UART2_MASK:
                        serial_data->offset[count] = MEN_UART2_OFFSET;
                        count++;
                        break;
                case MEN_UART3_MASK:
                        serial_data->offset[count] = MEN_UART3_OFFSET;
                        count++;
                        break;
                case MEN_UART4_MASK:
                        serial_data->offset[count] = MEN_UART4_OFFSET;
                        count++;
                        break;
                default:
                        return -EINVAL;
                }
        }

        if (count <= 0 || count > MEN_Z025_MAX_UARTS) {
                dev_err(&mdev->dev, "unexpected number of ports: %u\n",
                        count);
                return -ENODEV;
        }

        serial_data->num_ports = count;

        return 0;
}

static int init_serial_data(struct mcb_device *mdev,
                            struct resource *mem_res,
                            struct serial_8250_men_mcb_data *serial_data)
{
        switch (mdev->id) {
        case MEN_UART_ID_Z125:
                serial_data->num_ports = 1;
                serial_data->offset[0] = 0;
                return 0;
        case MEN_UART_ID_Z025:
        case MEN_UART_ID_Z057:
                return read_serial_data(mdev, mem_res, serial_data);
        default:
                dev_err(&mdev->dev, "no supported device!\n");
                return -ENODEV;
        }
}

static int serial_8250_men_mcb_probe(struct mcb_device *mdev,
                                     const struct mcb_device_id *id)
{
        struct uart_8250_port uart;
        struct serial_8250_men_mcb_data *data;
        struct resource *mem;
        int i;
        int res;

        mem = mcb_get_resource(mdev, IORESOURCE_MEM);
        if (mem == NULL)
                return -ENXIO;

        data = devm_kzalloc(&mdev->dev,
                            sizeof(struct serial_8250_men_mcb_data),
                            GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        res = init_serial_data(mdev, mem, data);
        if (res < 0)
                return res;

        dev_dbg(&mdev->dev, "found a 16z%03u with %u ports\n",
                mdev->id, data->num_ports);

        mcb_set_drvdata(mdev, data);

        for (i = 0; i < data->num_ports; i++) {
                memset(&uart, 0, sizeof(struct uart_8250_port));
                spin_lock_init(&uart.port.lock);

                uart.port.flags = UPF_SKIP_TEST |
                                  UPF_SHARE_IRQ |
                                  UPF_BOOT_AUTOCONF |
                                  UPF_IOREMAP;
                uart.port.iotype = UPIO_MEM;
                uart.port.uartclk = men_lookup_uartclk(mdev);
                uart.port.irq = mcb_get_irq(mdev);
                uart.port.mapbase = (unsigned long) mem->start
                                            + data->offset[i];

                /* ok, register the port */
                res = serial8250_register_8250_port(&uart);
                if (res < 0) {
                        dev_err(&mdev->dev, "unable to register UART port\n");
                        return res;
                }

                data->line[i] = res;
                dev_info(&mdev->dev, "found MCB UART: ttyS%d\n", data->line[i]);
        }

        return 0;
}

static void serial_8250_men_mcb_remove(struct mcb_device *mdev)
{
        int i;
        struct serial_8250_men_mcb_data *data = mcb_get_drvdata(mdev);

        if (!data)
                return;

        for (i = 0; i < data->num_ports; i++)
                serial8250_unregister_port(data->line[i]);
}

static const struct mcb_device_id serial_8250_men_mcb_ids[] = {
        { .device = MEN_UART_ID_Z025 },
        { .device = MEN_UART_ID_Z057 },
        { .device = MEN_UART_ID_Z125 },
        { }
};
MODULE_DEVICE_TABLE(mcb, serial_8250_men_mcb_ids);

static struct mcb_driver mcb_driver = {
        .driver = {
                .name = "8250_men_mcb",
        },
        .probe = serial_8250_men_mcb_probe,
        .remove = serial_8250_men_mcb_remove,
        .id_table = serial_8250_men_mcb_ids,
};
module_mcb_driver(mcb_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MEN 8250 UART driver");
MODULE_AUTHOR("Michael Moese <michael.moese@men.de");
MODULE_IMPORT_NS("MCB");