tty/serial/liteuart.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * LiteUART serial controller (LiteX) Driver
0004  *
0005  * Copyright (C) 2019-2020 Antmicro <www.antmicro.com>
0006  */
0007
0008 #include <linux/console.h>
0009 #include <linux/litex.h>
0010 #include <linux/module.h>
0011 #include <linux/of.h>
0012 #include <linux/of_address.h>
0013 #include <linux/of_platform.h>
0014 #include <linux/serial.h>
0015 #include <linux/serial_core.h>
0016 #include <linux/slab.h>
0017 #include <linux/timer.h>
0018 #include <linux/tty_flip.h>
0019 #include <linux/xarray.h>
0020
0021 /*
0022  * CSRs definitions (base address offsets + width)
0023  *
0024  * The definitions below are true for LiteX SoC configured for 8-bit CSR Bus,
0025  * 32-bit aligned.
0026  *
0027  * Supporting other configurations might require new definitions or a more
0028  * generic way of indexing the LiteX CSRs.
0029  *
0030  * For more details on how CSRs are defined and handled in LiteX, see comments
0031  * in the LiteX SoC Driver: drivers/soc/litex/litex_soc_ctrl.c
0032  */
0033 #define OFF_RXTX    0x00
0034 #define OFF_TXFULL  0x04
0035 #define OFF_RXEMPTY 0x08
0036 #define OFF_EV_STATUS   0x0c
0037 #define OFF_EV_PENDING  0x10
0038 #define OFF_EV_ENABLE   0x14
0039
0040 /* events */
0041 #define EV_TX       0x1
0042 #define EV_RX       0x2
0043
0044 struct liteuart_port {
0045     struct uart_port port;
0046     struct timer_list timer;
0047     u32 id;
0048 };
0049
0050 #define to_liteuart_port(port)  container_of(port, struct liteuart_port, port)
0051
0052 static DEFINE_XARRAY_FLAGS(liteuart_array, XA_FLAGS_ALLOC);
0053
0054 #ifdef CONFIG_SERIAL_LITEUART_CONSOLE
0055 static struct console liteuart_console;
0056 #endif
0057
0058 static struct uart_driver liteuart_driver = {
0059     .owner = THIS_MODULE,
0060     .driver_name = "liteuart",
0061     .dev_name = "ttyLXU",
0062     .major = 0,
0063     .minor = 0,
0064     .nr = CONFIG_SERIAL_LITEUART_MAX_PORTS,
0065 #ifdef CONFIG_SERIAL_LITEUART_CONSOLE
0066     .cons = &liteuart_console,
0067 #endif
0068 };
0069
0070 static void liteuart_timer(struct timer_list *t)
0071 {
0072     struct liteuart_port *uart = from_timer(uart, t, timer);
0073     struct uart_port *port = &uart->port;
0074     unsigned char __iomem *membase = port->membase;
0075     unsigned int flg = TTY_NORMAL;
0076     int ch;
0077     unsigned long status;
0078
0079     while ((status = !litex_read8(membase + OFF_RXEMPTY)) == 1) {
0080         ch = litex_read8(membase + OFF_RXTX);
0081         port->icount.rx++;
0082
0083         /* necessary for RXEMPTY to refresh its value */
0084         litex_write8(membase + OFF_EV_PENDING, EV_TX | EV_RX);
0085
0086         /* no overflow bits in status */
0087         if (!(uart_handle_sysrq_char(port, ch)))
0088             uart_insert_char(port, status, 0, ch, flg);
0089
0090         tty_flip_buffer_push(&port->state->port);
0091     }
0092
0093     mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
0094 }
0095
0096 static void liteuart_putchar(struct uart_port *port, unsigned char ch)
0097 {
0098     while (litex_read8(port->membase + OFF_TXFULL))
0099         cpu_relax();
0100
0101     litex_write8(port->membase + OFF_RXTX, ch);
0102 }
0103
0104 static unsigned int liteuart_tx_empty(struct uart_port *port)
0105 {
0106     /* not really tx empty, just checking if tx is not full */
0107     if (!litex_read8(port->membase + OFF_TXFULL))
0108         return TIOCSER_TEMT;
0109
0110     return 0;
0111 }
0112
0113 static void liteuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
0114 {
0115     /* modem control register is not present in LiteUART */
0116 }
0117
0118 static unsigned int liteuart_get_mctrl(struct uart_port *port)
0119 {
0120     return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
0121 }
0122
0123 static void liteuart_stop_tx(struct uart_port *port)
0124 {
0125 }
0126
0127 static void liteuart_start_tx(struct uart_port *port)
0128 {
0129     struct circ_buf *xmit = &port->state->xmit;
0130     unsigned char ch;
0131
0132     if (unlikely(port->x_char)) {
0133         litex_write8(port->membase + OFF_RXTX, port->x_char);
0134         port->icount.tx++;
0135         port->x_char = 0;
0136     } else if (!uart_circ_empty(xmit)) {
0137         while (xmit->head != xmit->tail) {
0138             ch = xmit->buf[xmit->tail];
0139             xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
0140             port->icount.tx++;
0141             liteuart_putchar(port, ch);
0142         }
0143     }
0144
0145     if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
0146         uart_write_wakeup(port);
0147 }
0148
0149 static void liteuart_stop_rx(struct uart_port *port)
0150 {
0151     struct liteuart_port *uart = to_liteuart_port(port);
0152
0153     /* just delete timer */
0154     del_timer(&uart->timer);
0155 }
0156
0157 static void liteuart_break_ctl(struct uart_port *port, int break_state)
0158 {
0159     /* LiteUART doesn't support sending break signal */
0160 }
0161
0162 static int liteuart_startup(struct uart_port *port)
0163 {
0164     struct liteuart_port *uart = to_liteuart_port(port);
0165
0166     /* disable events */
0167     litex_write8(port->membase + OFF_EV_ENABLE, 0);
0168
0169     /* prepare timer for polling */
0170     timer_setup(&uart->timer, liteuart_timer, 0);
0171     mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
0172
0173     return 0;
0174 }
0175
0176 static void liteuart_shutdown(struct uart_port *port)
0177 {
0178 }
0179
0180 static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
0181                  struct ktermios *old)
0182 {
0183     unsigned int baud;
0184     unsigned long flags;
0185
0186     spin_lock_irqsave(&port->lock, flags);
0187
0188     /* update baudrate */
0189     baud = uart_get_baud_rate(port, new, old, 0, 460800);
0190     uart_update_timeout(port, new->c_cflag, baud);
0191
0192     spin_unlock_irqrestore(&port->lock, flags);
0193 }
0194
0195 static const char *liteuart_type(struct uart_port *port)
0196 {
0197     return "liteuart";
0198 }
0199
0200 static void liteuart_release_port(struct uart_port *port)
0201 {
0202 }
0203
0204 static int liteuart_request_port(struct uart_port *port)
0205 {
0206     return 0;
0207 }
0208
0209 static void liteuart_config_port(struct uart_port *port, int flags)
0210 {
0211     /*
0212      * Driver core for serial ports forces a non-zero value for port type.
0213      * Write an arbitrary value here to accommodate the serial core driver,
0214      * as ID part of UAPI is redundant.
0215      */
0216     port->type = 1;
0217 }
0218
0219 static int liteuart_verify_port(struct uart_port *port,
0220                 struct serial_struct *ser)
0221 {
0222     if (port->type != PORT_UNKNOWN && ser->type != 1)
0223         return -EINVAL;
0224
0225     return 0;
0226 }
0227
0228 static const struct uart_ops liteuart_ops = {
0229     .tx_empty   = liteuart_tx_empty,
0230     .set_mctrl  = liteuart_set_mctrl,
0231     .get_mctrl  = liteuart_get_mctrl,
0232     .stop_tx    = liteuart_stop_tx,
0233     .start_tx   = liteuart_start_tx,
0234     .stop_rx    = liteuart_stop_rx,
0235     .break_ctl  = liteuart_break_ctl,
0236     .startup    = liteuart_startup,
0237     .shutdown   = liteuart_shutdown,
0238     .set_termios    = liteuart_set_termios,
0239     .type       = liteuart_type,
0240     .release_port   = liteuart_release_port,
0241     .request_port   = liteuart_request_port,
0242     .config_port    = liteuart_config_port,
0243     .verify_port    = liteuart_verify_port,
0244 };
0245
0246 static int liteuart_probe(struct platform_device *pdev)
0247 {
0248     struct liteuart_port *uart;
0249     struct uart_port *port;
0250     struct xa_limit limit;
0251     int dev_id, ret;
0252
0253     /* look for aliases; auto-enumerate for free index if not found */
0254     dev_id = of_alias_get_id(pdev->dev.of_node, "serial");
0255     if (dev_id < 0)
0256         limit = XA_LIMIT(0, CONFIG_SERIAL_LITEUART_MAX_PORTS);
0257     else
0258         limit = XA_LIMIT(dev_id, dev_id);
0259
0260     uart = devm_kzalloc(&pdev->dev, sizeof(struct liteuart_port), GFP_KERNEL);
0261     if (!uart)
0262         return -ENOMEM;
0263
0264     ret = xa_alloc(&liteuart_array, &dev_id, uart, limit, GFP_KERNEL);
0265     if (ret)
0266         return ret;
0267
0268     uart->id = dev_id;
0269     port = &uart->port;
0270
0271     /* get membase */
0272     port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
0273     if (IS_ERR(port->membase)) {
0274         ret = PTR_ERR(port->membase);
0275         goto err_erase_id;
0276     }
0277
0278     /* values not from device tree */
0279     port->dev = &pdev->dev;
0280     port->iotype = UPIO_MEM;
0281     port->flags = UPF_BOOT_AUTOCONF;
0282     port->ops = &liteuart_ops;
0283     port->regshift = 2;
0284     port->fifosize = 16;
0285     port->iobase = 1;
0286     port->type = PORT_UNKNOWN;
0287     port->line = dev_id;
0288     spin_lock_init(&port->lock);
0289
0290     platform_set_drvdata(pdev, port);
0291
0292     ret = uart_add_one_port(&liteuart_driver, &uart->port);
0293     if (ret)
0294         goto err_erase_id;
0295
0296     return 0;
0297
0298 err_erase_id:
0299     xa_erase(&liteuart_array, uart->id);
0300
0301     return ret;
0302 }
0303
0304 static int liteuart_remove(struct platform_device *pdev)
0305 {
0306     struct uart_port *port = platform_get_drvdata(pdev);
0307     struct liteuart_port *uart = to_liteuart_port(port);
0308
0309     uart_remove_one_port(&liteuart_driver, port);
0310     xa_erase(&liteuart_array, uart->id);
0311
0312     return 0;
0313 }
0314
0315 static const struct of_device_id liteuart_of_match[] = {
0316     { .compatible = "litex,liteuart" },
0317     {}
0318 };
0319 MODULE_DEVICE_TABLE(of, liteuart_of_match);
0320
0321 static struct platform_driver liteuart_platform_driver = {
0322     .probe = liteuart_probe,
0323     .remove = liteuart_remove,
0324     .driver = {
0325         .name = "liteuart",
0326         .of_match_table = liteuart_of_match,
0327     },
0328 };
0329
0330 #ifdef CONFIG_SERIAL_LITEUART_CONSOLE
0331
0332 static void liteuart_console_write(struct console *co, const char *s,
0333     unsigned int count)
0334 {
0335     struct liteuart_port *uart;
0336     struct uart_port *port;
0337     unsigned long flags;
0338
0339     uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
0340     port = &uart->port;
0341
0342     spin_lock_irqsave(&port->lock, flags);
0343     uart_console_write(port, s, count, liteuart_putchar);
0344     spin_unlock_irqrestore(&port->lock, flags);
0345 }
0346
0347 static int liteuart_console_setup(struct console *co, char *options)
0348 {
0349     struct liteuart_port *uart;
0350     struct uart_port *port;
0351     int baud = 115200;
0352     int bits = 8;
0353     int parity = 'n';
0354     int flow = 'n';
0355
0356     uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
0357     if (!uart)
0358         return -ENODEV;
0359
0360     port = &uart->port;
0361     if (!port->membase)
0362         return -ENODEV;
0363
0364     if (options)
0365         uart_parse_options(options, &baud, &parity, &bits, &flow);
0366
0367     return uart_set_options(port, co, baud, parity, bits, flow);
0368 }
0369
0370 static struct console liteuart_console = {
0371     .name = "liteuart",
0372     .write = liteuart_console_write,
0373     .device = uart_console_device,
0374     .setup = liteuart_console_setup,
0375     .flags = CON_PRINTBUFFER,
0376     .index = -1,
0377     .data = &liteuart_driver,
0378 };
0379
0380 static int __init liteuart_console_init(void)
0381 {
0382     register_console(&liteuart_console);
0383
0384     return 0;
0385 }
0386 console_initcall(liteuart_console_init);
0387
0388 static void early_liteuart_write(struct console *console, const char *s,
0389                     unsigned int count)
0390 {
0391     struct earlycon_device *device = console->data;
0392     struct uart_port *port = &device->port;
0393
0394     uart_console_write(port, s, count, liteuart_putchar);
0395 }
0396
0397 static int __init early_liteuart_setup(struct earlycon_device *device,
0398                        const char *options)
0399 {
0400     if (!device->port.membase)
0401         return -ENODEV;
0402
0403     device->con->write = early_liteuart_write;
0404     return 0;
0405 }
0406
0407 OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup);
0408 #endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
0409
0410 static int __init liteuart_init(void)
0411 {
0412     int res;
0413
0414     res = uart_register_driver(&liteuart_driver);
0415     if (res)
0416         return res;
0417
0418     res = platform_driver_register(&liteuart_platform_driver);
0419     if (res) {
0420         uart_unregister_driver(&liteuart_driver);
0421         return res;
0422     }
0423
0424     return 0;
0425 }
0426
0427 static void __exit liteuart_exit(void)
0428 {
0429     platform_driver_unregister(&liteuart_platform_driver);
0430     uart_unregister_driver(&liteuart_driver);
0431 }
0432
0433 module_init(liteuart_init);
0434 module_exit(liteuart_exit);
0435
0436 MODULE_AUTHOR("Antmicro <www.antmicro.com>");
0437 MODULE_DESCRIPTION("LiteUART serial driver");
0438 MODULE_LICENSE("GPL v2");
0439 MODULE_ALIAS("platform:liteuart");