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 #include <linux/of_platform.h>
43 /*************************************
44 * ARC UART Hardware Specs
45 ************************************/
46 #define ARC_UART_TX_FIFO_SIZE 1
49 * UART Register set (this is not a Standards Compliant IP)
50 * Also each reg is Word aligned, but only 8 bits wide
61 /* Bits for UART Status Reg (R/W) */
62 #define RXIENB 0x04 /* Receive Interrupt Enable */
63 #define TXIENB 0x40 /* Transmit Interrupt Enable */
65 #define RXEMPTY 0x20 /* Receive FIFO Empty: No char receivede */
66 #define TXEMPTY 0x80 /* Transmit FIFO Empty, thus char can be written into */
68 #define RXFULL 0x08 /* Receive FIFO full */
69 #define RXFULL1 0x10 /* Receive FIFO has space for 1 char (tot space=4) */
71 #define RXFERR 0x01 /* Frame Error: Stop Bit not detected */
72 #define RXOERR 0x02 /* OverFlow Err: Char recv but RXFULL still set */
74 /* Uart bit fiddling helpers: lowest level */
75 #define RBASE(port, reg) (port->membase + reg)
76 #define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
77 #define UART_REG_GET(u, r) readb(RBASE(u, r))
79 #define UART_REG_OR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) | (v))
80 #define UART_REG_CLR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) & ~(v))
82 /* Uart bit fiddling helpers: API level */
83 #define UART_SET_DATA(uart, val) UART_REG_SET(uart, R_DATA, val)
84 #define UART_GET_DATA(uart) UART_REG_GET(uart, R_DATA)
86 #define UART_SET_BAUDH(uart, val) UART_REG_SET(uart, R_BAUDH, val)
87 #define UART_SET_BAUDL(uart, val) UART_REG_SET(uart, R_BAUDL, val)
89 #define UART_CLR_STATUS(uart, val) UART_REG_CLR(uart, R_STS, val)
90 #define UART_GET_STATUS(uart) UART_REG_GET(uart, R_STS)
92 #define UART_ALL_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB|TXIENB)
93 #define UART_RX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB)
94 #define UART_TX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, TXIENB)
96 #define UART_ALL_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB|TXIENB)
97 #define UART_RX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB)
98 #define UART_TX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, TXIENB)
100 #define ARC_SERIAL_DEV_NAME "ttyARC"
102 struct arc_uart_port {
103 struct uart_port port;
105 int is_emulated; /* H/w vs. Instruction Set Simulator */
108 #define to_arc_port(uport) container_of(uport, struct arc_uart_port, port)
110 static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];
112 #ifdef CONFIG_SERIAL_ARC_CONSOLE
113 static struct console arc_console;
116 #define DRIVER_NAME "arc-uart"
118 static struct uart_driver arc_uart_driver = {
119 .owner = THIS_MODULE,
120 .driver_name = DRIVER_NAME,
121 .dev_name = ARC_SERIAL_DEV_NAME,
124 .nr = CONFIG_SERIAL_ARC_NR_PORTS,
125 #ifdef CONFIG_SERIAL_ARC_CONSOLE
126 .cons = &arc_console,
130 static void arc_serial_stop_rx(struct uart_port *port)
132 UART_RX_IRQ_DISABLE(port);
135 static void arc_serial_stop_tx(struct uart_port *port)
137 while (!(UART_GET_STATUS(port) & TXEMPTY))
140 UART_TX_IRQ_DISABLE(port);
144 * Return TIOCSER_TEMT when transmitter is not busy.
146 static unsigned int arc_serial_tx_empty(struct uart_port *port)
150 stat = UART_GET_STATUS(port);
158 * Driver internal routine, used by both tty(serial core) as well as tx-isr
159 * -Called under spinlock in either cases
160 * -also tty->stopped has already been checked
161 * = by uart_start( ) before calling us
162 * = tx_ist checks that too before calling
164 static void arc_serial_tx_chars(struct uart_port *port)
166 struct circ_buf *xmit = &port->state->xmit;
170 if (unlikely(port->x_char)) {
171 UART_SET_DATA(port, port->x_char);
175 } else if (xmit->tail != xmit->head) { /* TODO: uart_circ_empty */
176 ch = xmit->buf[xmit->tail];
177 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
179 while (!(UART_GET_STATUS(port) & TXEMPTY))
181 UART_SET_DATA(port, ch);
186 * If num chars in xmit buffer are too few, ask tty layer for more.
187 * By Hard ISR to schedule processing in software interrupt part
189 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
190 uart_write_wakeup(port);
193 UART_TX_IRQ_ENABLE(port);
197 * port is locked and interrupts are disabled
198 * uart_start( ) calls us under the port spinlock irqsave
200 static void arc_serial_start_tx(struct uart_port *port)
202 arc_serial_tx_chars(port);
205 static void arc_serial_rx_chars(struct uart_port *port, unsigned int status)
207 unsigned int ch, flg = 0;
210 * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
211 * is very subtle. Here's how ...
212 * Upon getting a RX-Intr, such that RX-EMPTY=0, meaning data available,
213 * driver reads the DATA Reg and keeps doing that in a loop, until
214 * RX-EMPTY=1. Multiple chars being avail, with a single Interrupt,
215 * before RX-EMPTY=0, implies some sort of buffering going on in the
216 * controller, which is indeed the Rx-FIFO.
220 * This could be an Rx Intr for err (no data),
221 * so check err and clear that Intr first
223 if (unlikely(status & (RXOERR | RXFERR))) {
224 if (status & RXOERR) {
225 port->icount.overrun++;
227 UART_CLR_STATUS(port, RXOERR);
230 if (status & RXFERR) {
231 port->icount.frame++;
233 UART_CLR_STATUS(port, RXFERR);
238 if (status & RXEMPTY)
241 ch = UART_GET_DATA(port);
244 if (!(uart_handle_sysrq_char(port, ch)))
245 uart_insert_char(port, status, RXOERR, ch, flg);
247 spin_unlock(&port->lock);
248 tty_flip_buffer_push(&port->state->port);
249 spin_lock(&port->lock);
250 } while (!((status = UART_GET_STATUS(port)) & RXEMPTY));
254 * A note on the Interrupt handling state machine of this driver
256 * kernel printk writes funnel thru the console driver framework and in order
257 * to keep things simple as well as efficient, it writes to UART in polled
258 * mode, in one shot, and exits.
260 * OTOH, Userland output (via tty layer), uses interrupt based writes as there
261 * can be undeterministic delay between char writes.
263 * Thus Rx-interrupts are always enabled, while tx-interrupts are by default
266 * When tty has some data to send out, serial core calls driver's start_tx
268 * -checks-if-tty-buffer-has-char-to-send
269 * -writes-data-to-uart
272 * Once data bits are pushed out, controller raises the Tx-room-avail-Interrupt.
273 * The first thing Tx ISR does is disable further Tx interrupts (as this could
274 * be the last char to send, before settling down into the quiet polled mode).
275 * It then calls the exact routine used by tty layer write to send out any
276 * more char in tty buffer. In case of sending, it re-enables Tx-intr. In case
277 * of no data, it remains disabled.
278 * This is how the transmit state machine is dynamically switched on/off
281 static irqreturn_t arc_serial_isr(int irq, void *dev_id)
283 struct uart_port *port = dev_id;
286 status = UART_GET_STATUS(port);
289 * Single IRQ for both Rx (data available) Tx (room available) Interrupt
290 * notifications from the UART Controller.
291 * To demultiplex between the two, we check the relevant bits
293 if (status & RXIENB) {
295 /* already in ISR, no need of xx_irqsave */
296 spin_lock(&port->lock);
297 arc_serial_rx_chars(port, status);
298 spin_unlock(&port->lock);
301 if ((status & TXIENB) && (status & TXEMPTY)) {
303 /* Unconditionally disable further Tx-Interrupts.
304 * will be enabled by tx_chars() if needed.
306 UART_TX_IRQ_DISABLE(port);
308 spin_lock(&port->lock);
310 if (!uart_tx_stopped(port))
311 arc_serial_tx_chars(port);
313 spin_unlock(&port->lock);
319 static unsigned int arc_serial_get_mctrl(struct uart_port *port)
322 * Pretend we have a Modem status reg and following bits are
323 * always set, to satify the serial core state machine
324 * (DSR) Data Set Ready
325 * (CTS) Clear To Send
326 * (CAR) Carrier Detect
328 return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
331 static void arc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
333 /* MCR not present */
336 static void arc_serial_break_ctl(struct uart_port *port, int break_state)
338 /* ARC UART doesn't support sending Break signal */
341 static int arc_serial_startup(struct uart_port *port)
343 /* Before we hook up the ISR, Disable all UART Interrupts */
344 UART_ALL_IRQ_DISABLE(port);
346 if (request_irq(port->irq, arc_serial_isr, 0, "arc uart rx-tx", port)) {
347 dev_warn(port->dev, "Unable to attach ARC UART intr\n");
351 UART_RX_IRQ_ENABLE(port); /* Only Rx IRQ enabled to begin with */
356 /* This is not really needed */
357 static void arc_serial_shutdown(struct uart_port *port)
359 free_irq(port->irq, port);
363 arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
364 struct ktermios *old)
366 struct arc_uart_port *uart = to_arc_port(port);
367 unsigned int baud, uartl, uarth, hw_val;
371 * Use the generic handler so that any specially encoded baud rates
372 * such as SPD_xx flags or "%B0" can be handled
373 * Max Baud I suppose will not be more than current 115K * 4
374 * Formula for ARC UART is: hw-val = ((CLK/(BAUD*4)) -1)
375 * spread over two 8-bit registers
377 baud = uart_get_baud_rate(port, new, old, 0, 460800);
379 hw_val = port->uartclk / (uart->baud * 4) - 1;
380 uartl = hw_val & 0xFF;
381 uarth = (hw_val >> 8) & 0xFF;
384 * UART ISS(Instruction Set simulator) emulation has a subtle bug:
385 * A existing value of Baudh = 0 is used as a indication to startup
386 * it's internal state machine.
387 * Thus if baudh is set to 0, 2 times, it chokes.
388 * This happens with BAUD=115200 and the formaula above
389 * Until that is fixed, when running on ISS, we will set baudh to !0
391 if (uart->is_emulated)
394 spin_lock_irqsave(&port->lock, flags);
396 UART_ALL_IRQ_DISABLE(port);
398 UART_SET_BAUDL(port, uartl);
399 UART_SET_BAUDH(port, uarth);
401 UART_RX_IRQ_ENABLE(port);
404 * UART doesn't support Parity/Hardware Flow Control;
405 * Only supports 8N1 character size
407 new->c_cflag &= ~(CMSPAR|CRTSCTS|CSIZE);
411 tty_termios_copy_hw(new, old);
413 /* Don't rewrite B0 */
414 if (tty_termios_baud_rate(new))
415 tty_termios_encode_baud_rate(new, baud, baud);
417 uart_update_timeout(port, new->c_cflag, baud);
419 spin_unlock_irqrestore(&port->lock, flags);
422 static const char *arc_serial_type(struct uart_port *port)
424 return port->type == PORT_ARC ? DRIVER_NAME : NULL;
427 static void arc_serial_release_port(struct uart_port *port)
431 static int arc_serial_request_port(struct uart_port *port)
437 * Verify the new serial_struct (for TIOCSSERIAL).
440 arc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
442 if (port->type != PORT_UNKNOWN && ser->type != PORT_ARC)
449 * Configure/autoconfigure the port.
451 static void arc_serial_config_port(struct uart_port *port, int flags)
453 if (flags & UART_CONFIG_TYPE)
454 port->type = PORT_ARC;
457 #if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_ARC_CONSOLE)
459 static void arc_serial_poll_putchar(struct uart_port *port, int chr)
461 while (!(UART_GET_STATUS(port) & TXEMPTY))
464 UART_SET_DATA(port, (unsigned char)chr);
468 #ifdef CONFIG_CONSOLE_POLL
469 static int arc_serial_poll_getchar(struct uart_port *port)
473 while (!(UART_GET_STATUS(port) & RXEMPTY))
476 chr = UART_GET_DATA(port);
481 static struct uart_ops arc_serial_pops = {
482 .tx_empty = arc_serial_tx_empty,
483 .set_mctrl = arc_serial_set_mctrl,
484 .get_mctrl = arc_serial_get_mctrl,
485 .stop_tx = arc_serial_stop_tx,
486 .start_tx = arc_serial_start_tx,
487 .stop_rx = arc_serial_stop_rx,
488 .break_ctl = arc_serial_break_ctl,
489 .startup = arc_serial_startup,
490 .shutdown = arc_serial_shutdown,
491 .set_termios = arc_serial_set_termios,
492 .type = arc_serial_type,
493 .release_port = arc_serial_release_port,
494 .request_port = arc_serial_request_port,
495 .config_port = arc_serial_config_port,
496 .verify_port = arc_serial_verify_port,
497 #ifdef CONFIG_CONSOLE_POLL
498 .poll_put_char = arc_serial_poll_putchar,
499 .poll_get_char = arc_serial_poll_getchar,
504 arc_uart_init_one(struct platform_device *pdev, int dev_id)
506 struct resource *res, *res2;
507 unsigned long *plat_data;
508 struct arc_uart_port *uart = &arc_uart_ports[dev_id];
509 struct uart_port *port = &uart->port;
511 plat_data = dev_get_platdata(&pdev->dev);
515 uart->is_emulated = !!plat_data[0]; /* workaround ISS bug */
517 if (is_early_platform_device(pdev)) {
518 port->uartclk = plat_data[1];
519 uart->baud = plat_data[2];
521 struct device_node *np = pdev->dev.of_node;
524 if (of_property_read_u32(np, "clock-frequency", &val)) {
525 dev_err(&pdev->dev, "clock-frequency property NOTset\n");
530 if (of_property_read_u32(np, "current-speed", &val)) {
531 dev_err(&pdev->dev, "current-speed property NOT set\n");
537 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
541 res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
545 port->mapbase = res->start;
546 port->membase = ioremap_nocache(res->start, resource_size(res));
548 /* No point of dev_err since UART itself is hosed here */
551 port->irq = res2->start;
552 port->dev = &pdev->dev;
553 port->iotype = UPIO_MEM;
554 port->flags = UPF_BOOT_AUTOCONF;
556 port->ops = &arc_serial_pops;
558 port->fifosize = ARC_UART_TX_FIFO_SIZE;
561 * uart_insert_char( ) uses it in decideding whether to ignore a
562 * char or not. Explicitly setting it here, removes the subtelty
564 port->ignore_status_mask = 0;
569 #ifdef CONFIG_SERIAL_ARC_CONSOLE
571 static int arc_serial_console_setup(struct console *co, char *options)
573 struct uart_port *port;
579 if (co->index < 0 || co->index >= CONFIG_SERIAL_ARC_NR_PORTS)
583 * The uart port backing the console (e.g. ttyARC1) might not have been
584 * init yet. If so, defer the console setup to after the port.
586 port = &arc_uart_ports[co->index].port;
591 uart_parse_options(options, &baud, &parity, &bits, &flow);
594 * Serial core will call port->ops->set_termios( )
595 * which will set the baud reg
597 return uart_set_options(port, co, baud, parity, bits, flow);
601 * Interrupts are disabled on entering
603 static void arc_serial_console_write(struct console *co, const char *s,
606 struct uart_port *port = &arc_uart_ports[co->index].port;
609 spin_lock_irqsave(&port->lock, flags);
610 uart_console_write(port, s, count, arc_serial_poll_putchar);
611 spin_unlock_irqrestore(&port->lock, flags);
614 static struct console arc_console = {
615 .name = ARC_SERIAL_DEV_NAME,
616 .write = arc_serial_console_write,
617 .device = uart_console_device,
618 .setup = arc_serial_console_setup,
619 .flags = CON_PRINTBUFFER,
621 .data = &arc_uart_driver
624 static __init void early_serial_write(struct console *con, const char *s,
627 struct uart_port *port = &arc_uart_ports[con->index].port;
629 uart_console_write(port, s, n, arc_serial_poll_putchar);
632 static struct console arc_early_serial_console __initdata = {
633 .name = "early_ARCuart",
634 .write = early_serial_write,
635 .flags = CON_PRINTBUFFER | CON_BOOT,
639 static int __init arc_serial_probe_earlyprintk(struct platform_device *pdev)
641 int dev_id = pdev->id < 0 ? 0 : pdev->id;
644 arc_early_serial_console.index = dev_id;
646 rc = arc_uart_init_one(pdev, dev_id);
648 panic("early console init failed\n");
650 arc_serial_console_setup(&arc_early_serial_console, NULL);
652 register_console(&arc_early_serial_console);
655 #endif /* CONFIG_SERIAL_ARC_CONSOLE */
657 static int arc_serial_probe(struct platform_device *pdev)
660 struct device_node *np = pdev->dev.of_node;
662 /* no device tree device */
666 dev_id = of_alias_get_id(np, "serial");
670 rc = arc_uart_init_one(pdev, dev_id);
674 rc = uart_add_one_port(&arc_uart_driver, &arc_uart_ports[dev_id].port);
678 static int arc_serial_remove(struct platform_device *pdev)
680 /* This will never be called */
684 static const struct of_device_id arc_uart_dt_ids[] = {
685 { .compatible = "snps,arc-uart" },
688 MODULE_DEVICE_TABLE(of, arc_uart_dt_ids);
690 static struct platform_driver arc_platform_driver = {
691 .probe = arc_serial_probe,
692 .remove = arc_serial_remove,
695 .owner = THIS_MODULE,
696 .of_match_table = arc_uart_dt_ids,
700 #ifdef CONFIG_SERIAL_ARC_CONSOLE
702 static struct platform_driver early_arc_platform_driver __initdata = {
703 .probe = arc_serial_probe_earlyprintk,
704 .remove = arc_serial_remove,
707 .owner = THIS_MODULE,
711 * Register an early platform driver of "earlyprintk" class.
712 * ARCH platform code installs the driver and probes the early devices
713 * The installation could rely on user specifying earlyprintk=xyx in cmd line
714 * or it could be done independently, for all "earlyprintk" class drivers.
715 * [see arch/arc/plat-arcfpga/platform.c]
717 early_platform_init("earlyprintk", &early_arc_platform_driver);
719 #endif /* CONFIG_SERIAL_ARC_CONSOLE */
721 static int __init arc_serial_init(void)
725 ret = uart_register_driver(&arc_uart_driver);
729 ret = platform_driver_register(&arc_platform_driver);
731 uart_unregister_driver(&arc_uart_driver);
736 static void __exit arc_serial_exit(void)
738 platform_driver_unregister(&arc_platform_driver);
739 uart_unregister_driver(&arc_uart_driver);
742 module_init(arc_serial_init);
743 module_exit(arc_serial_exit);
745 MODULE_LICENSE("GPL");
746 MODULE_ALIAS("platform:" DRIVER_NAME);
747 MODULE_AUTHOR("Vineet Gupta");
748 MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");