2 * ARC On-Chip(fpga) UART Driver
4 * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.com)
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
10 * vineetg: July 10th 2012
11 * -Decoupled the driver from arch/arc
12 * +Using platform_get_resource() for irq/membase (thx to bfin_uart.c)
13 * +Using early_platform_xxx() for early console (thx to mach-shmobile/xxx)
15 * Vineetg: Aug 21st 2010
16 * -Is uart_tx_stopped() not done in tty write path as it has already been
17 * taken care of, in serial core
19 * Vineetg: Aug 18th 2010
20 * -New Serial Core based ARC UART driver
21 * -Derived largely from blackfin driver albiet with some major tweaks
24 * -check if sysreq works
27 #if defined(CONFIG_SERIAL_ARC_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
31 #include <linux/module.h>
32 #include <linux/serial.h>
33 #include <linux/console.h>
34 #include <linux/sysrq.h>
35 #include <linux/platform_device.h>
36 #include <linux/tty.h>
37 #include <linux/tty_flip.h>
38 #include <linux/serial_core.h>
41 /*************************************
42 * ARC UART Hardware Specs
43 ************************************/
44 #define ARC_UART_TX_FIFO_SIZE 1
47 * UART Register set (this is not a Standards Compliant IP)
48 * Also each reg is Word aligned, but only 8 bits wide
59 /* Bits for UART Status Reg (R/W) */
60 #define RXIENB 0x04 /* Receive Interrupt Enable */
61 #define TXIENB 0x40 /* Transmit Interrupt Enable */
63 #define RXEMPTY 0x20 /* Receive FIFO Empty: No char receivede */
64 #define TXEMPTY 0x80 /* Transmit FIFO Empty, thus char can be written into */
66 #define RXFULL 0x08 /* Receive FIFO full */
67 #define RXFULL1 0x10 /* Receive FIFO has space for 1 char (tot space=4) */
69 #define RXFERR 0x01 /* Frame Error: Stop Bit not detected */
70 #define RXOERR 0x02 /* OverFlow Err: Char recv but RXFULL still set */
72 /* Uart bit fiddling helpers: lowest level */
73 #define RBASE(uart, reg) (uart->port.membase + reg)
74 #define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
75 #define UART_REG_GET(u, r) readb(RBASE(u, r))
77 #define UART_REG_OR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) | (v))
78 #define UART_REG_CLR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) & ~(v))
80 /* Uart bit fiddling helpers: API level */
81 #define UART_SET_DATA(uart, val) UART_REG_SET(uart, R_DATA, val)
82 #define UART_GET_DATA(uart) UART_REG_GET(uart, R_DATA)
84 #define UART_SET_BAUDH(uart, val) UART_REG_SET(uart, R_BAUDH, val)
85 #define UART_SET_BAUDL(uart, val) UART_REG_SET(uart, R_BAUDL, val)
87 #define UART_CLR_STATUS(uart, val) UART_REG_CLR(uart, R_STS, val)
88 #define UART_GET_STATUS(uart) UART_REG_GET(uart, R_STS)
90 #define UART_ALL_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB|TXIENB)
91 #define UART_RX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB)
92 #define UART_TX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, TXIENB)
94 #define UART_ALL_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB|TXIENB)
95 #define UART_RX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB)
96 #define UART_TX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, TXIENB)
98 #define ARC_SERIAL_DEV_NAME "ttyARC"
100 struct arc_uart_port {
101 struct uart_port port;
103 int is_emulated; /* H/w vs. Instruction Set Simulator */
106 #define to_arc_port(uport) container_of(uport, struct arc_uart_port, port)
108 static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];
110 #ifdef CONFIG_SERIAL_ARC_CONSOLE
111 static struct console arc_console;
114 #define DRIVER_NAME "arc-uart"
116 static struct uart_driver arc_uart_driver = {
117 .owner = THIS_MODULE,
118 .driver_name = DRIVER_NAME,
119 .dev_name = ARC_SERIAL_DEV_NAME,
122 .nr = CONFIG_SERIAL_ARC_NR_PORTS,
123 #ifdef CONFIG_SERIAL_ARC_CONSOLE
124 .cons = &arc_console,
128 static void arc_serial_stop_rx(struct uart_port *port)
130 struct arc_uart_port *uart = to_arc_port(port);
132 UART_RX_IRQ_DISABLE(uart);
135 static void arc_serial_stop_tx(struct uart_port *port)
137 struct arc_uart_port *uart = to_arc_port(port);
139 while (!(UART_GET_STATUS(uart) & TXEMPTY))
142 UART_TX_IRQ_DISABLE(uart);
146 * Return TIOCSER_TEMT when transmitter is not busy.
148 static unsigned int arc_serial_tx_empty(struct uart_port *port)
150 struct arc_uart_port *uart = to_arc_port(port);
153 stat = UART_GET_STATUS(uart);
161 * Driver internal routine, used by both tty(serial core) as well as tx-isr
162 * -Called under spinlock in either cases
163 * -also tty->stopped / tty->hw_stopped has already been checked
164 * = by uart_start( ) before calling us
165 * = tx_ist checks that too before calling
167 static void arc_serial_tx_chars(struct arc_uart_port *uart)
169 struct circ_buf *xmit = &uart->port.state->xmit;
173 if (unlikely(uart->port.x_char)) {
174 UART_SET_DATA(uart, uart->port.x_char);
175 uart->port.icount.tx++;
176 uart->port.x_char = 0;
178 } else if (xmit->tail != xmit->head) { /* TODO: uart_circ_empty */
179 ch = xmit->buf[xmit->tail];
180 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
181 uart->port.icount.tx++;
182 while (!(UART_GET_STATUS(uart) & TXEMPTY))
184 UART_SET_DATA(uart, ch);
189 * If num chars in xmit buffer are too few, ask tty layer for more.
190 * By Hard ISR to schedule processing in software interrupt part
192 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
193 uart_write_wakeup(&uart->port);
196 UART_TX_IRQ_ENABLE(uart);
200 * port is locked and interrupts are disabled
201 * uart_start( ) calls us under the port spinlock irqsave
203 static void arc_serial_start_tx(struct uart_port *port)
205 struct arc_uart_port *uart = to_arc_port(port);
207 arc_serial_tx_chars(uart);
210 static void arc_serial_rx_chars(struct arc_uart_port *uart)
212 struct tty_struct *tty = tty_port_tty_get(&uart->port.state->port);
213 unsigned int status, ch, flg = 0;
219 * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
220 * is very subtle. Here's how ...
221 * Upon getting a RX-Intr, such that RX-EMPTY=0, meaning data available,
222 * driver reads the DATA Reg and keeps doing that in a loop, until
223 * RX-EMPTY=1. Multiple chars being avail, with a single Interrupt,
224 * before RX-EMPTY=0, implies some sort of buffering going on in the
225 * controller, which is indeed the Rx-FIFO.
227 while (!((status = UART_GET_STATUS(uart)) & RXEMPTY)) {
229 ch = UART_GET_DATA(uart);
230 uart->port.icount.rx++;
232 if (unlikely(status & (RXOERR | RXFERR))) {
233 if (status & RXOERR) {
234 uart->port.icount.overrun++;
236 UART_CLR_STATUS(uart, RXOERR);
239 if (status & RXFERR) {
240 uart->port.icount.frame++;
242 UART_CLR_STATUS(uart, RXFERR);
247 if (unlikely(uart_handle_sysrq_char(&uart->port, ch)))
250 uart_insert_char(&uart->port, status, RXOERR, ch, flg);
253 tty_flip_buffer_push(tty);
260 * A note on the Interrupt handling state machine of this driver
262 * kernel printk writes funnel thru the console driver framework and in order
263 * to keep things simple as well as efficient, it writes to UART in polled
264 * mode, in one shot, and exits.
266 * OTOH, Userland output (via tty layer), uses interrupt based writes as there
267 * can be undeterministic delay between char writes.
269 * Thus Rx-interrupts are always enabled, while tx-interrupts are by default
272 * When tty has some data to send out, serial core calls driver's start_tx
274 * -checks-if-tty-buffer-has-char-to-send
275 * -writes-data-to-uart
278 * Once data bits are pushed out, controller raises the Tx-room-avail-Interrupt.
279 * The first thing Tx ISR does is disable further Tx interrupts (as this could
280 * be the last char to send, before settling down into the quiet polled mode).
281 * It then calls the exact routine used by tty layer write to send out any
282 * more char in tty buffer. In case of sending, it re-enables Tx-intr. In case
283 * of no data, it remains disabled.
284 * This is how the transmit state machine is dynamically switched on/off
287 static irqreturn_t arc_serial_isr(int irq, void *dev_id)
289 struct arc_uart_port *uart = dev_id;
292 status = UART_GET_STATUS(uart);
295 * Single IRQ for both Rx (data available) Tx (room available) Interrupt
296 * notifications from the UART Controller.
297 * To demultiplex between the two, we check the relevant bits
299 if ((status & RXIENB) && !(status & RXEMPTY)) {
301 /* already in ISR, no need of xx_irqsave */
302 spin_lock(&uart->port.lock);
303 arc_serial_rx_chars(uart);
304 spin_unlock(&uart->port.lock);
307 if ((status & TXIENB) && (status & TXEMPTY)) {
309 /* Unconditionally disable further Tx-Interrupts.
310 * will be enabled by tx_chars() if needed.
312 UART_TX_IRQ_DISABLE(uart);
314 spin_lock(&uart->port.lock);
316 if (!uart_tx_stopped(&uart->port))
317 arc_serial_tx_chars(uart);
319 spin_unlock(&uart->port.lock);
325 static unsigned int arc_serial_get_mctrl(struct uart_port *port)
328 * Pretend we have a Modem status reg and following bits are
329 * always set, to satify the serial core state machine
330 * (DSR) Data Set Ready
331 * (CTS) Clear To Send
332 * (CAR) Carrier Detect
334 return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
337 static void arc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
339 /* MCR not present */
342 /* Enable Modem Status Interrupts */
344 static void arc_serial_enable_ms(struct uart_port *port)
346 /* MSR not present */
349 static void arc_serial_break_ctl(struct uart_port *port, int break_state)
351 /* ARC UART doesn't support sending Break signal */
354 static int arc_serial_startup(struct uart_port *port)
356 struct arc_uart_port *uart = to_arc_port(port);
358 /* Before we hook up the ISR, Disable all UART Interrupts */
359 UART_ALL_IRQ_DISABLE(uart);
361 if (request_irq(uart->port.irq, arc_serial_isr, 0, "arc uart rx-tx",
363 dev_warn(uart->port.dev, "Unable to attach ARC UART intr\n");
367 UART_RX_IRQ_ENABLE(uart); /* Only Rx IRQ enabled to begin with */
372 /* This is not really needed */
373 static void arc_serial_shutdown(struct uart_port *port)
375 struct arc_uart_port *uart = to_arc_port(port);
376 free_irq(uart->port.irq, uart);
380 arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
381 struct ktermios *old)
383 struct arc_uart_port *uart = to_arc_port(port);
384 unsigned int baud, uartl, uarth, hw_val;
388 * Use the generic handler so that any specially encoded baud rates
389 * such as SPD_xx flags or "%B0" can be handled
390 * Max Baud I suppose will not be more than current 115K * 4
391 * Formula for ARC UART is: hw-val = ((CLK/(BAUD*4)) -1)
392 * spread over two 8-bit registers
394 baud = uart_get_baud_rate(port, new, old, 0, 460800);
396 hw_val = port->uartclk / (uart->baud * 4) - 1;
397 uartl = hw_val & 0xFF;
398 uarth = (hw_val >> 8) & 0xFF;
401 * UART ISS(Instruction Set simulator) emulation has a subtle bug:
402 * A existing value of Baudh = 0 is used as a indication to startup
403 * it's internal state machine.
404 * Thus if baudh is set to 0, 2 times, it chokes.
405 * This happens with BAUD=115200 and the formaula above
406 * Until that is fixed, when running on ISS, we will set baudh to !0
408 if (uart->is_emulated)
411 spin_lock_irqsave(&port->lock, flags);
413 UART_ALL_IRQ_DISABLE(uart);
415 UART_SET_BAUDL(uart, uartl);
416 UART_SET_BAUDH(uart, uarth);
418 UART_RX_IRQ_ENABLE(uart);
421 * UART doesn't support Parity/Hardware Flow Control;
422 * Only supports 8N1 character size
424 new->c_cflag &= ~(CMSPAR|CRTSCTS|CSIZE);
428 tty_termios_copy_hw(new, old);
430 /* Don't rewrite B0 */
431 if (tty_termios_baud_rate(new))
432 tty_termios_encode_baud_rate(new, baud, baud);
434 uart_update_timeout(port, new->c_cflag, baud);
436 spin_unlock_irqrestore(&port->lock, flags);
439 static const char *arc_serial_type(struct uart_port *port)
441 struct arc_uart_port *uart = to_arc_port(port);
443 return uart->port.type == PORT_ARC ? DRIVER_NAME : NULL;
446 static void arc_serial_release_port(struct uart_port *port)
450 static int arc_serial_request_port(struct uart_port *port)
456 * Verify the new serial_struct (for TIOCSSERIAL).
459 arc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
461 if (port->type != PORT_UNKNOWN && ser->type != PORT_ARC)
468 * Configure/autoconfigure the port.
470 static void arc_serial_config_port(struct uart_port *port, int flags)
472 struct arc_uart_port *uart = to_arc_port(port);
474 if (flags & UART_CONFIG_TYPE)
475 uart->port.type = PORT_ARC;
478 #if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_ARC_CONSOLE)
480 static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
482 struct arc_uart_port *uart = to_arc_port(port);
484 while (!(UART_GET_STATUS(uart) & TXEMPTY))
487 UART_SET_DATA(uart, chr);
491 #ifdef CONFIG_CONSOLE_POLL
492 static int arc_serial_poll_getchar(struct uart_port *port)
494 struct arc_uart_port *uart = to_arc_port(port);
497 while (!(UART_GET_STATUS(uart) & RXEMPTY))
500 chr = UART_GET_DATA(uart);
505 static struct uart_ops arc_serial_pops = {
506 .tx_empty = arc_serial_tx_empty,
507 .set_mctrl = arc_serial_set_mctrl,
508 .get_mctrl = arc_serial_get_mctrl,
509 .stop_tx = arc_serial_stop_tx,
510 .start_tx = arc_serial_start_tx,
511 .stop_rx = arc_serial_stop_rx,
512 .enable_ms = arc_serial_enable_ms,
513 .break_ctl = arc_serial_break_ctl,
514 .startup = arc_serial_startup,
515 .shutdown = arc_serial_shutdown,
516 .set_termios = arc_serial_set_termios,
517 .type = arc_serial_type,
518 .release_port = arc_serial_release_port,
519 .request_port = arc_serial_request_port,
520 .config_port = arc_serial_config_port,
521 .verify_port = arc_serial_verify_port,
522 #ifdef CONFIG_CONSOLE_POLL
523 .poll_put_char = arc_serial_poll_putchar,
524 .poll_get_char = arc_serial_poll_getchar,
529 arc_uart_init_one(struct platform_device *pdev, struct arc_uart_port *uart)
531 struct resource *res, *res2;
532 unsigned long *plat_data;
534 if (pdev->id < 0 || pdev->id >= CONFIG_SERIAL_ARC_NR_PORTS) {
535 dev_err(&pdev->dev, "Wrong uart platform device id.\n");
539 plat_data = ((unsigned long *)(pdev->dev.platform_data));
540 uart->baud = plat_data[0];
542 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
546 res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
550 uart->port.mapbase = res->start;
551 uart->port.membase = ioremap_nocache(res->start, resource_size(res));
552 if (!uart->port.membase)
553 /* No point of dev_err since UART itself is hosed here */
556 uart->port.irq = res2->start;
557 uart->port.dev = &pdev->dev;
558 uart->port.iotype = UPIO_MEM;
559 uart->port.flags = UPF_BOOT_AUTOCONF;
560 uart->port.line = pdev->id;
561 uart->port.ops = &arc_serial_pops;
563 uart->port.uartclk = plat_data[1];
564 uart->port.fifosize = ARC_UART_TX_FIFO_SIZE;
567 * uart_insert_char( ) uses it in decideding whether to ignore a
568 * char or not. Explicitly setting it here, removes the subtelty
570 uart->port.ignore_status_mask = 0;
572 /* Real Hardware vs. emulated to work around a bug */
573 uart->is_emulated = !!plat_data[2];
578 #ifdef CONFIG_SERIAL_ARC_CONSOLE
580 static int arc_serial_console_setup(struct console *co, char *options)
582 struct uart_port *port;
588 if (co->index < 0 || co->index >= CONFIG_SERIAL_ARC_NR_PORTS)
592 * The uart port backing the console (e.g. ttyARC1) might not have been
593 * init yet. If so, defer the console setup to after the port.
595 port = &arc_uart_ports[co->index].port;
600 uart_parse_options(options, &baud, &parity, &bits, &flow);
603 * Serial core will call port->ops->set_termios( )
604 * which will set the baud reg
606 return uart_set_options(port, co, baud, parity, bits, flow);
609 static void arc_serial_console_putchar(struct uart_port *port, int ch)
611 arc_serial_poll_putchar(port, (unsigned char)ch);
615 * Interrupts are disabled on entering
617 static void arc_serial_console_write(struct console *co, const char *s,
620 struct uart_port *port = &arc_uart_ports[co->index].port;
623 spin_lock_irqsave(&port->lock, flags);
624 uart_console_write(port, s, count, arc_serial_console_putchar);
625 spin_unlock_irqrestore(&port->lock, flags);
628 static struct console arc_console = {
629 .name = ARC_SERIAL_DEV_NAME,
630 .write = arc_serial_console_write,
631 .device = uart_console_device,
632 .setup = arc_serial_console_setup,
633 .flags = CON_PRINTBUFFER,
635 .data = &arc_uart_driver
638 static __init void early_serial_write(struct console *con, const char *s,
641 struct uart_port *port = &arc_uart_ports[con->index].port;
644 for (i = 0; i < n; i++, s++) {
646 arc_serial_poll_putchar(port, '\r');
647 arc_serial_poll_putchar(port, *s);
651 static struct __initdata console arc_early_serial_console = {
652 .name = "early_ARCuart",
653 .write = early_serial_write,
654 .flags = CON_PRINTBUFFER | CON_BOOT,
658 static int arc_serial_probe_earlyprintk(struct platform_device *pdev)
660 arc_early_serial_console.index = pdev->id;
662 arc_uart_init_one(pdev, &arc_uart_ports[pdev->id]);
664 arc_serial_console_setup(&arc_early_serial_console, NULL);
666 register_console(&arc_early_serial_console);
670 static int arc_serial_probe_earlyprintk(struct platform_device *pdev)
674 #endif /* CONFIG_SERIAL_ARC_CONSOLE */
676 static int arc_serial_probe(struct platform_device *pdev)
678 struct arc_uart_port *uart;
681 if (is_early_platform_device(pdev))
682 return arc_serial_probe_earlyprintk(pdev);
684 uart = &arc_uart_ports[pdev->id];
685 rc = arc_uart_init_one(pdev, uart);
689 return uart_add_one_port(&arc_uart_driver, &uart->port);
692 static int arc_serial_remove(struct platform_device *pdev)
694 /* This will never be called */
698 static struct platform_driver arc_platform_driver = {
699 .probe = arc_serial_probe,
700 .remove = arc_serial_remove,
703 .owner = THIS_MODULE,
707 #ifdef CONFIG_SERIAL_ARC_CONSOLE
709 * Register an early platform driver of "earlyprintk" class.
710 * ARCH platform code installs the driver and probes the early devices
711 * The installation could rely on user specifying earlyprintk=xyx in cmd line
712 * or it could be done independently, for all "earlyprintk" class drivers.
713 * [see arch/arc/plat-arcfpga/platform.c]
715 early_platform_init("earlyprintk", &arc_platform_driver);
717 #endif /* CONFIG_SERIAL_ARC_CONSOLE */
719 static int __init arc_serial_init(void)
723 ret = uart_register_driver(&arc_uart_driver);
727 ret = platform_driver_register(&arc_platform_driver);
729 uart_unregister_driver(&arc_uart_driver);
734 static void __exit arc_serial_exit(void)
736 platform_driver_unregister(&arc_platform_driver);
737 uart_unregister_driver(&arc_uart_driver);
740 module_init(arc_serial_init);
741 module_exit(arc_serial_exit);
743 MODULE_LICENSE("GPL");
744 MODULE_ALIAS("plat-arcfpga/uart");
745 MODULE_AUTHOR("Vineet Gupta");
746 MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");