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0001 // SPDX-License-Identifier: GPL-2.0+
0002 /*
0003  *  Driver for Conexant Digicolor serial ports (USART)
0004  *
0005  * Author: Baruch Siach <baruch@tkos.co.il>
0006  *
0007  * Copyright (C) 2014 Paradox Innovation Ltd.
0008  */
0009 
0010 #include <linux/module.h>
0011 #include <linux/console.h>
0012 #include <linux/serial_core.h>
0013 #include <linux/serial.h>
0014 #include <linux/clk.h>
0015 #include <linux/io.h>
0016 #include <linux/tty.h>
0017 #include <linux/tty_flip.h>
0018 #include <linux/of.h>
0019 #include <linux/platform_device.h>
0020 #include <linux/workqueue.h>
0021 
0022 #define UA_ENABLE           0x00
0023 #define UA_ENABLE_ENABLE        BIT(0)
0024 
0025 #define UA_CONTROL          0x01
0026 #define UA_CONTROL_RX_ENABLE        BIT(0)
0027 #define UA_CONTROL_TX_ENABLE        BIT(1)
0028 #define UA_CONTROL_SOFT_RESET       BIT(2)
0029 
0030 #define UA_STATUS           0x02
0031 #define UA_STATUS_PARITY_ERR        BIT(0)
0032 #define UA_STATUS_FRAME_ERR     BIT(1)
0033 #define UA_STATUS_OVERRUN_ERR       BIT(2)
0034 #define UA_STATUS_TX_READY      BIT(6)
0035 
0036 #define UA_CONFIG           0x03
0037 #define UA_CONFIG_CHAR_LEN      BIT(0)
0038 #define UA_CONFIG_STOP_BITS     BIT(1)
0039 #define UA_CONFIG_PARITY        BIT(2)
0040 #define UA_CONFIG_ODD_PARITY        BIT(4)
0041 
0042 #define UA_EMI_REC          0x04
0043 
0044 #define UA_HBAUD_LO         0x08
0045 #define UA_HBAUD_HI         0x09
0046 
0047 #define UA_STATUS_FIFO          0x0a
0048 #define UA_STATUS_FIFO_RX_EMPTY     BIT(2)
0049 #define UA_STATUS_FIFO_RX_INT_ALMOST    BIT(3)
0050 #define UA_STATUS_FIFO_TX_FULL      BIT(4)
0051 #define UA_STATUS_FIFO_TX_INT_ALMOST    BIT(7)
0052 
0053 #define UA_CONFIG_FIFO          0x0b
0054 #define UA_CONFIG_FIFO_RX_THRESH    7
0055 #define UA_CONFIG_FIFO_RX_FIFO_MODE BIT(3)
0056 #define UA_CONFIG_FIFO_TX_FIFO_MODE BIT(7)
0057 
0058 #define UA_INTFLAG_CLEAR        0x1c
0059 #define UA_INTFLAG_SET          0x1d
0060 #define UA_INT_ENABLE           0x1e
0061 #define UA_INT_STATUS           0x1f
0062 
0063 #define UA_INT_TX           BIT(0)
0064 #define UA_INT_RX           BIT(1)
0065 
0066 #define DIGICOLOR_USART_NR      3
0067 
0068 /*
0069  * We use the 16 bytes hardware FIFO to buffer Rx traffic. Rx interrupt is
0070  * only produced when the FIFO is filled more than a certain configurable
0071  * threshold. Unfortunately, there is no way to set this threshold below half
0072  * FIFO. This means that we must periodically poll the FIFO status register to
0073  * see whether there are waiting Rx bytes.
0074  */
0075 
0076 struct digicolor_port {
0077     struct uart_port port;
0078     struct delayed_work rx_poll_work;
0079 };
0080 
0081 static struct uart_port *digicolor_ports[DIGICOLOR_USART_NR];
0082 
0083 static bool digicolor_uart_tx_full(struct uart_port *port)
0084 {
0085     return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
0086           UA_STATUS_FIFO_TX_FULL);
0087 }
0088 
0089 static bool digicolor_uart_rx_empty(struct uart_port *port)
0090 {
0091     return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
0092           UA_STATUS_FIFO_RX_EMPTY);
0093 }
0094 
0095 static void digicolor_uart_stop_tx(struct uart_port *port)
0096 {
0097     u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
0098 
0099     int_enable &= ~UA_INT_TX;
0100     writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
0101 }
0102 
0103 static void digicolor_uart_start_tx(struct uart_port *port)
0104 {
0105     u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
0106 
0107     int_enable |= UA_INT_TX;
0108     writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
0109 }
0110 
0111 static void digicolor_uart_stop_rx(struct uart_port *port)
0112 {
0113     u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);
0114 
0115     int_enable &= ~UA_INT_RX;
0116     writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
0117 }
0118 
0119 static void digicolor_rx_poll(struct work_struct *work)
0120 {
0121     struct digicolor_port *dp =
0122         container_of(to_delayed_work(work),
0123                  struct digicolor_port, rx_poll_work);
0124 
0125     if (!digicolor_uart_rx_empty(&dp->port))
0126         /* force RX interrupt */
0127         writeb_relaxed(UA_INT_RX, dp->port.membase + UA_INTFLAG_SET);
0128 
0129     schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));
0130 }
0131 
0132 static void digicolor_uart_rx(struct uart_port *port)
0133 {
0134     unsigned long flags;
0135 
0136     spin_lock_irqsave(&port->lock, flags);
0137 
0138     while (1) {
0139         u8 status, ch;
0140         unsigned int ch_flag;
0141 
0142         if (digicolor_uart_rx_empty(port))
0143             break;
0144 
0145         ch = readb_relaxed(port->membase + UA_EMI_REC);
0146         status = readb_relaxed(port->membase + UA_STATUS);
0147 
0148         port->icount.rx++;
0149         ch_flag = TTY_NORMAL;
0150 
0151         if (status) {
0152             if (status & UA_STATUS_PARITY_ERR)
0153                 port->icount.parity++;
0154             else if (status & UA_STATUS_FRAME_ERR)
0155                 port->icount.frame++;
0156             else if (status & UA_STATUS_OVERRUN_ERR)
0157                 port->icount.overrun++;
0158 
0159             status &= port->read_status_mask;
0160 
0161             if (status & UA_STATUS_PARITY_ERR)
0162                 ch_flag = TTY_PARITY;
0163             else if (status & UA_STATUS_FRAME_ERR)
0164                 ch_flag = TTY_FRAME;
0165             else if (status & UA_STATUS_OVERRUN_ERR)
0166                 ch_flag = TTY_OVERRUN;
0167         }
0168 
0169         if (status & port->ignore_status_mask)
0170             continue;
0171 
0172         uart_insert_char(port, status, UA_STATUS_OVERRUN_ERR, ch,
0173                  ch_flag);
0174     }
0175 
0176     spin_unlock_irqrestore(&port->lock, flags);
0177 
0178     tty_flip_buffer_push(&port->state->port);
0179 }
0180 
0181 static void digicolor_uart_tx(struct uart_port *port)
0182 {
0183     struct circ_buf *xmit = &port->state->xmit;
0184     unsigned long flags;
0185 
0186     if (digicolor_uart_tx_full(port))
0187         return;
0188 
0189     spin_lock_irqsave(&port->lock, flags);
0190 
0191     if (port->x_char) {
0192         writeb_relaxed(port->x_char, port->membase + UA_EMI_REC);
0193         port->icount.tx++;
0194         port->x_char = 0;
0195         goto out;
0196     }
0197 
0198     if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
0199         digicolor_uart_stop_tx(port);
0200         goto out;
0201     }
0202 
0203     while (!uart_circ_empty(xmit)) {
0204         writeb(xmit->buf[xmit->tail], port->membase + UA_EMI_REC);
0205         xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
0206         port->icount.tx++;
0207 
0208         if (digicolor_uart_tx_full(port))
0209             break;
0210     }
0211 
0212     if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
0213         uart_write_wakeup(port);
0214 
0215 out:
0216     spin_unlock_irqrestore(&port->lock, flags);
0217 }
0218 
0219 static irqreturn_t digicolor_uart_int(int irq, void *dev_id)
0220 {
0221     struct uart_port *port = dev_id;
0222     u8 int_status = readb_relaxed(port->membase + UA_INT_STATUS);
0223 
0224     writeb_relaxed(UA_INT_RX | UA_INT_TX,
0225                port->membase + UA_INTFLAG_CLEAR);
0226 
0227     if (int_status & UA_INT_RX)
0228         digicolor_uart_rx(port);
0229     if (int_status & UA_INT_TX)
0230         digicolor_uart_tx(port);
0231 
0232     return IRQ_HANDLED;
0233 }
0234 
0235 static unsigned int digicolor_uart_tx_empty(struct uart_port *port)
0236 {
0237     u8 status = readb_relaxed(port->membase + UA_STATUS);
0238 
0239     return (status & UA_STATUS_TX_READY) ? TIOCSER_TEMT : 0;
0240 }
0241 
0242 static unsigned int digicolor_uart_get_mctrl(struct uart_port *port)
0243 {
0244     return TIOCM_CTS;
0245 }
0246 
0247 static void digicolor_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
0248 {
0249 }
0250 
0251 static void digicolor_uart_break_ctl(struct uart_port *port, int state)
0252 {
0253 }
0254 
0255 static int digicolor_uart_startup(struct uart_port *port)
0256 {
0257     struct digicolor_port *dp =
0258         container_of(port, struct digicolor_port, port);
0259 
0260     writeb_relaxed(UA_ENABLE_ENABLE, port->membase + UA_ENABLE);
0261     writeb_relaxed(UA_CONTROL_SOFT_RESET, port->membase + UA_CONTROL);
0262     writeb_relaxed(0, port->membase + UA_CONTROL);
0263 
0264     writeb_relaxed(UA_CONFIG_FIFO_RX_FIFO_MODE
0265                | UA_CONFIG_FIFO_TX_FIFO_MODE | UA_CONFIG_FIFO_RX_THRESH,
0266                port->membase + UA_CONFIG_FIFO);
0267     writeb_relaxed(UA_STATUS_FIFO_RX_INT_ALMOST,
0268                port->membase + UA_STATUS_FIFO);
0269     writeb_relaxed(UA_CONTROL_RX_ENABLE | UA_CONTROL_TX_ENABLE,
0270                port->membase + UA_CONTROL);
0271     writeb_relaxed(UA_INT_TX | UA_INT_RX,
0272                port->membase + UA_INT_ENABLE);
0273 
0274     schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));
0275 
0276     return 0;
0277 }
0278 
0279 static void digicolor_uart_shutdown(struct uart_port *port)
0280 {
0281     struct digicolor_port *dp =
0282         container_of(port, struct digicolor_port, port);
0283 
0284     writeb_relaxed(0, port->membase + UA_ENABLE);
0285     cancel_delayed_work_sync(&dp->rx_poll_work);
0286 }
0287 
0288 static void digicolor_uart_set_termios(struct uart_port *port,
0289                        struct ktermios *termios,
0290                        struct ktermios *old)
0291 {
0292     unsigned int baud, divisor;
0293     u8 config = 0;
0294     unsigned long flags;
0295 
0296     /* Mask termios capabilities we don't support */
0297     termios->c_cflag &= ~CMSPAR;
0298     termios->c_iflag &= ~(BRKINT | IGNBRK);
0299 
0300     /* Limit baud rates so that we don't need the fractional divider */
0301     baud = uart_get_baud_rate(port, termios, old,
0302                   port->uartclk / (0x10000*16),
0303                   port->uartclk / 256);
0304     divisor = uart_get_divisor(port, baud) - 1;
0305 
0306     switch (termios->c_cflag & CSIZE) {
0307     case CS7:
0308         break;
0309     case CS8:
0310     default:
0311         config |= UA_CONFIG_CHAR_LEN;
0312         termios->c_cflag &= ~CSIZE;
0313         termios->c_cflag |= CS8;
0314         break;
0315     }
0316 
0317     if (termios->c_cflag & CSTOPB)
0318         config |= UA_CONFIG_STOP_BITS;
0319 
0320     if (termios->c_cflag & PARENB) {
0321         config |= UA_CONFIG_PARITY;
0322         if (termios->c_cflag & PARODD)
0323             config |= UA_CONFIG_ODD_PARITY;
0324     }
0325 
0326     /* Set read status mask */
0327     port->read_status_mask = UA_STATUS_OVERRUN_ERR;
0328     if (termios->c_iflag & INPCK)
0329         port->read_status_mask |= UA_STATUS_PARITY_ERR
0330             | UA_STATUS_FRAME_ERR;
0331 
0332     /* Set status ignore mask */
0333     port->ignore_status_mask = 0;
0334     if (!(termios->c_cflag & CREAD))
0335         port->ignore_status_mask |= UA_STATUS_OVERRUN_ERR
0336             | UA_STATUS_PARITY_ERR | UA_STATUS_FRAME_ERR;
0337 
0338     spin_lock_irqsave(&port->lock, flags);
0339 
0340     uart_update_timeout(port, termios->c_cflag, baud);
0341 
0342     writeb_relaxed(config, port->membase + UA_CONFIG);
0343     writeb_relaxed(divisor & 0xff, port->membase + UA_HBAUD_LO);
0344     writeb_relaxed(divisor >> 8, port->membase + UA_HBAUD_HI);
0345 
0346     spin_unlock_irqrestore(&port->lock, flags);
0347 }
0348 
0349 static const char *digicolor_uart_type(struct uart_port *port)
0350 {
0351     return (port->type == PORT_DIGICOLOR) ? "DIGICOLOR USART" : NULL;
0352 }
0353 
0354 static void digicolor_uart_config_port(struct uart_port *port, int flags)
0355 {
0356     if (flags & UART_CONFIG_TYPE)
0357         port->type = PORT_DIGICOLOR;
0358 }
0359 
0360 static void digicolor_uart_release_port(struct uart_port *port)
0361 {
0362 }
0363 
0364 static int digicolor_uart_request_port(struct uart_port *port)
0365 {
0366     return 0;
0367 }
0368 
0369 static const struct uart_ops digicolor_uart_ops = {
0370     .tx_empty   = digicolor_uart_tx_empty,
0371     .set_mctrl  = digicolor_uart_set_mctrl,
0372     .get_mctrl  = digicolor_uart_get_mctrl,
0373     .stop_tx    = digicolor_uart_stop_tx,
0374     .start_tx   = digicolor_uart_start_tx,
0375     .stop_rx    = digicolor_uart_stop_rx,
0376     .break_ctl  = digicolor_uart_break_ctl,
0377     .startup    = digicolor_uart_startup,
0378     .shutdown   = digicolor_uart_shutdown,
0379     .set_termios    = digicolor_uart_set_termios,
0380     .type       = digicolor_uart_type,
0381     .config_port    = digicolor_uart_config_port,
0382     .release_port   = digicolor_uart_release_port,
0383     .request_port   = digicolor_uart_request_port,
0384 };
0385 
0386 static void digicolor_uart_console_putchar(struct uart_port *port, unsigned char ch)
0387 {
0388     while (digicolor_uart_tx_full(port))
0389         cpu_relax();
0390 
0391     writeb_relaxed(ch, port->membase + UA_EMI_REC);
0392 }
0393 
0394 static void digicolor_uart_console_write(struct console *co, const char *c,
0395                      unsigned n)
0396 {
0397     struct uart_port *port = digicolor_ports[co->index];
0398     u8 status;
0399     unsigned long flags;
0400     int locked = 1;
0401 
0402     if (oops_in_progress)
0403         locked = spin_trylock_irqsave(&port->lock, flags);
0404     else
0405         spin_lock_irqsave(&port->lock, flags);
0406 
0407     uart_console_write(port, c, n, digicolor_uart_console_putchar);
0408 
0409     if (locked)
0410         spin_unlock_irqrestore(&port->lock, flags);
0411 
0412     /* Wait for transmitter to become empty */
0413     do {
0414         status = readb_relaxed(port->membase + UA_STATUS);
0415     } while ((status & UA_STATUS_TX_READY) == 0);
0416 }
0417 
0418 static int digicolor_uart_console_setup(struct console *co, char *options)
0419 {
0420     int baud = 115200, bits = 8, parity = 'n', flow = 'n';
0421     struct uart_port *port;
0422 
0423     if (co->index < 0 || co->index >= DIGICOLOR_USART_NR)
0424         return -EINVAL;
0425 
0426     port = digicolor_ports[co->index];
0427     if (!port)
0428         return -ENODEV;
0429 
0430     if (options)
0431         uart_parse_options(options, &baud, &parity, &bits, &flow);
0432 
0433     return uart_set_options(port, co, baud, parity, bits, flow);
0434 }
0435 
0436 static struct console digicolor_console = {
0437     .name   = "ttyS",
0438     .device = uart_console_device,
0439     .write  = digicolor_uart_console_write,
0440     .setup  = digicolor_uart_console_setup,
0441     .flags  = CON_PRINTBUFFER,
0442     .index  = -1,
0443 };
0444 
0445 static struct uart_driver digicolor_uart = {
0446     .driver_name    = "digicolor-usart",
0447     .dev_name   = "ttyS",
0448     .nr     = DIGICOLOR_USART_NR,
0449 };
0450 
0451 static int digicolor_uart_probe(struct platform_device *pdev)
0452 {
0453     struct device_node *np = pdev->dev.of_node;
0454     int irq, ret, index;
0455     struct digicolor_port *dp;
0456     struct resource *res;
0457     struct clk *uart_clk;
0458 
0459     if (!np) {
0460         dev_err(&pdev->dev, "Missing device tree node\n");
0461         return -ENXIO;
0462     }
0463 
0464     index = of_alias_get_id(np, "serial");
0465     if (index < 0 || index >= DIGICOLOR_USART_NR)
0466         return -EINVAL;
0467 
0468     dp = devm_kzalloc(&pdev->dev, sizeof(*dp), GFP_KERNEL);
0469     if (!dp)
0470         return -ENOMEM;
0471 
0472     uart_clk = devm_clk_get(&pdev->dev, NULL);
0473     if (IS_ERR(uart_clk))
0474         return PTR_ERR(uart_clk);
0475 
0476     dp->port.membase = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
0477     if (IS_ERR(dp->port.membase))
0478         return PTR_ERR(dp->port.membase);
0479     dp->port.mapbase = res->start;
0480 
0481     irq = platform_get_irq(pdev, 0);
0482     if (irq < 0)
0483         return irq;
0484     dp->port.irq = irq;
0485 
0486     dp->port.iotype = UPIO_MEM;
0487     dp->port.uartclk = clk_get_rate(uart_clk);
0488     dp->port.fifosize = 16;
0489     dp->port.dev = &pdev->dev;
0490     dp->port.ops = &digicolor_uart_ops;
0491     dp->port.line = index;
0492     dp->port.type = PORT_DIGICOLOR;
0493     spin_lock_init(&dp->port.lock);
0494 
0495     digicolor_ports[index] = &dp->port;
0496     platform_set_drvdata(pdev, &dp->port);
0497 
0498     INIT_DELAYED_WORK(&dp->rx_poll_work, digicolor_rx_poll);
0499 
0500     ret = devm_request_irq(&pdev->dev, dp->port.irq, digicolor_uart_int, 0,
0501                    dev_name(&pdev->dev), &dp->port);
0502     if (ret)
0503         return ret;
0504 
0505     return uart_add_one_port(&digicolor_uart, &dp->port);
0506 }
0507 
0508 static int digicolor_uart_remove(struct platform_device *pdev)
0509 {
0510     struct uart_port *port = platform_get_drvdata(pdev);
0511 
0512     uart_remove_one_port(&digicolor_uart, port);
0513 
0514     return 0;
0515 }
0516 
0517 static const struct of_device_id digicolor_uart_dt_ids[] = {
0518     { .compatible = "cnxt,cx92755-usart", },
0519     { }
0520 };
0521 MODULE_DEVICE_TABLE(of, digicolor_uart_dt_ids);
0522 
0523 static struct platform_driver digicolor_uart_platform = {
0524     .driver = {
0525         .name       = "digicolor-usart",
0526         .of_match_table = of_match_ptr(digicolor_uart_dt_ids),
0527     },
0528     .probe  = digicolor_uart_probe,
0529     .remove = digicolor_uart_remove,
0530 };
0531 
0532 static int __init digicolor_uart_init(void)
0533 {
0534     int ret;
0535 
0536     if (IS_ENABLED(CONFIG_SERIAL_CONEXANT_DIGICOLOR_CONSOLE)) {
0537         digicolor_uart.cons = &digicolor_console;
0538         digicolor_console.data = &digicolor_uart;
0539     }
0540 
0541     ret = uart_register_driver(&digicolor_uart);
0542     if (ret)
0543         return ret;
0544 
0545     ret = platform_driver_register(&digicolor_uart_platform);
0546     if (ret)
0547         uart_unregister_driver(&digicolor_uart);
0548 
0549     return ret;
0550 }
0551 module_init(digicolor_uart_init);
0552 
0553 static void __exit digicolor_uart_exit(void)
0554 {
0555     platform_driver_unregister(&digicolor_uart_platform);
0556     uart_unregister_driver(&digicolor_uart);
0557 }
0558 module_exit(digicolor_uart_exit);
0559 
0560 MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
0561 MODULE_DESCRIPTION("Conexant Digicolor USART serial driver");
0562 MODULE_LICENSE("GPL");
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