arc_uart.c
// SPDX-License-Identifier: GPL-2.0
/*
* ARC On-Chip(fpga) UART Driver
*
* Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.com)
*
* vineetg: July 10th 2012
* -Decoupled the driver from arch/arc
* +Using platform_get_resource() for irq/membase (thx to bfin_uart.c)
* +Using early_platform_xxx() for early console (thx to mach-shmobile/xxx)
*
* Vineetg: Aug 21st 2010
* -Is uart_tx_stopped() not done in tty write path as it has already been
* taken care of, in serial core
*
* Vineetg: Aug 18th 2010
* -New Serial Core based ARC UART driver
* -Derived largely from blackfin driver albiet with some major tweaks
*
* TODO:
* -check if sysreq works
*/
#if defined(CONFIG_SERIAL_ARC_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif
#include <linux/module.h>
#include <linux/serial.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/platform_device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/io.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>
/*************************************
* ARC UART Hardware Specs
************************************/
#define ARC_UART_TX_FIFO_SIZE 1
/*
* UART Register set (this is not a Standards Compliant IP)
* Also each reg is Word aligned, but only 8 bits wide
*/
#define R_ID0 0
#define R_ID1 4
#define R_ID2 8
#define R_ID3 12
#define R_DATA 16
#define R_STS 20
#define R_BAUDL 24
#define R_BAUDH 28
/* Bits for UART Status Reg (R/W) */
#define RXIENB 0x04 /* Receive Interrupt Enable */
#define TXIENB 0x40 /* Transmit Interrupt Enable */
#define RXEMPTY 0x20 /* Receive FIFO Empty: No char receivede */
#define TXEMPTY 0x80 /* Transmit FIFO Empty, thus char can be written into */
#define RXFULL 0x08 /* Receive FIFO full */
#define RXFULL1 0x10 /* Receive FIFO has space for 1 char (tot space=4) */
#define RXFERR 0x01 /* Frame Error: Stop Bit not detected */
#define RXOERR 0x02 /* OverFlow Err: Char recv but RXFULL still set */
/* Uart bit fiddling helpers: lowest level */
#define RBASE(port, reg) (port->membase + reg)
#define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
#define UART_REG_GET(u, r) readb(RBASE(u, r))
#define UART_REG_OR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) | (v))
#define UART_REG_CLR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) & ~(v))
/* Uart bit fiddling helpers: API level */
#define UART_SET_DATA(uart, val) UART_REG_SET(uart, R_DATA, val)
#define UART_GET_DATA(uart) UART_REG_GET(uart, R_DATA)
#define UART_SET_BAUDH(uart, val) UART_REG_SET(uart, R_BAUDH, val)
#define UART_SET_BAUDL(uart, val) UART_REG_SET(uart, R_BAUDL, val)
#define UART_CLR_STATUS(uart, val) UART_REG_CLR(uart, R_STS, val)
#define UART_GET_STATUS(uart) UART_REG_GET(uart, R_STS)
#define UART_ALL_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB|TXIENB)
#define UART_RX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB)
#define UART_TX_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, TXIENB)
#define UART_ALL_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB|TXIENB)
#define UART_RX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, RXIENB)
#define UART_TX_IRQ_ENABLE(uart) UART_REG_OR(uart, R_STS, TXIENB)
#define ARC_SERIAL_DEV_NAME "ttyARC"
struct arc_uart_port {
struct uart_port port;
unsigned long baud;
};
#define to_arc_port(uport) container_of(uport, struct arc_uart_port, port)
static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];
#ifdef CONFIG_SERIAL_ARC_CONSOLE
static struct console arc_console;
#endif
#define DRIVER_NAME "arc-uart"
static struct uart_driver arc_uart_driver = {
.owner = THIS_MODULE,
.driver_name = DRIVER_NAME,
.dev_name = ARC_SERIAL_DEV_NAME,
.major = 0,
.minor = 0,
.nr = CONFIG_SERIAL_ARC_NR_PORTS,
#ifdef CONFIG_SERIAL_ARC_CONSOLE
.cons = &arc_console,
#endif
};
static void arc_serial_stop_rx(struct uart_port *port)
{
UART_RX_IRQ_DISABLE(port);
}
static void arc_serial_stop_tx(struct uart_port *port)
{
while (!(UART_GET_STATUS(port) & TXEMPTY))
cpu_relax();
UART_TX_IRQ_DISABLE(port);
}
/*
* Return TIOCSER_TEMT when transmitter is not busy.
*/
static unsigned int arc_serial_tx_empty(struct uart_port *port)
{
unsigned int stat;
stat = UART_GET_STATUS(port);
if (stat & TXEMPTY)
return TIOCSER_TEMT;
return 0;
}
/*
* Driver internal routine, used by both tty(serial core) as well as tx-isr
* -Called under spinlock in either cases
* -also tty->stopped has already been checked
* = by uart_start( ) before calling us
* = tx_ist checks that too before calling
*/
static void arc_serial_tx_chars(struct uart_port *port)
{
struct circ_buf *xmit = &port->state->xmit;
int sent = 0;
unsigned char ch;
if (unlikely(port->x_char)) {
UART_SET_DATA(port, port->x_char);
port->icount.tx++;
port->x_char = 0;
sent = 1;
} else if (!uart_circ_empty(xmit)) {
ch = xmit->buf[xmit->tail];
xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
port->icount.tx++;
while (!(UART_GET_STATUS(port) & TXEMPTY))
cpu_relax();
UART_SET_DATA(port, ch);
sent = 1;
}
/*
* If num chars in xmit buffer are too few, ask tty layer for more.
* By Hard ISR to schedule processing in software interrupt part
*/
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port);
if (sent)
UART_TX_IRQ_ENABLE(port);
}
/*
* port is locked and interrupts are disabled
* uart_start( ) calls us under the port spinlock irqsave
*/
static void arc_serial_start_tx(struct uart_port *port)
{
arc_serial_tx_chars(port);
}
static void arc_serial_rx_chars(struct uart_port *port, unsigned int status)
{
unsigned int ch, flg = 0;
/*
* UART has 4 deep RX-FIFO. Driver's recongnition of this fact
* is very subtle. Here's how ...
* Upon getting a RX-Intr, such that RX-EMPTY=0, meaning data available,
* driver reads the DATA Reg and keeps doing that in a loop, until
* RX-EMPTY=1. Multiple chars being avail, with a single Interrupt,
* before RX-EMPTY=0, implies some sort of buffering going on in the
* controller, which is indeed the Rx-FIFO.
*/
do {
/*
* This could be an Rx Intr for err (no data),
* so check err and clear that Intr first
*/
if (unlikely(status & (RXOERR | RXFERR))) {
if (status & RXOERR) {
port->icount.overrun++;
flg = TTY_OVERRUN;
UART_CLR_STATUS(port, RXOERR);
}
if (status & RXFERR) {
port->icount.frame++;
flg = TTY_FRAME;
UART_CLR_STATUS(port, RXFERR);
}
} else
flg = TTY_NORMAL;
if (status & RXEMPTY)
continue;
ch = UART_GET_DATA(port);
port->icount.rx++;
if (!(uart_handle_sysrq_char(port, ch)))
uart_insert_char(port, status, RXOERR, ch, flg);
spin_unlock(&port->lock);
tty_flip_buffer_push(&port->state->port);
spin_lock(&port->lock);
} while (!((status = UART_GET_STATUS(port)) & RXEMPTY));
}
/*
* A note on the Interrupt handling state machine of this driver
*
* kernel printk writes funnel thru the console driver framework and in order
* to keep things simple as well as efficient, it writes to UART in polled
* mode, in one shot, and exits.
*
* OTOH, Userland output (via tty layer), uses interrupt based writes as there
* can be undeterministic delay between char writes.
*
* Thus Rx-interrupts are always enabled, while tx-interrupts are by default
* disabled.
*
* When tty has some data to send out, serial core calls driver's start_tx
* which
* -checks-if-tty-buffer-has-char-to-send
* -writes-data-to-uart
* -enable-tx-intr
*
* Once data bits are pushed out, controller raises the Tx-room-avail-Interrupt.
* The first thing Tx ISR does is disable further Tx interrupts (as this could
* be the last char to send, before settling down into the quiet polled mode).
* It then calls the exact routine used by tty layer write to send out any
* more char in tty buffer. In case of sending, it re-enables Tx-intr. In case
* of no data, it remains disabled.
* This is how the transmit state machine is dynamically switched on/off
*/
static irqreturn_t arc_serial_isr(int irq, void *dev_id)
{
struct uart_port *port = dev_id;
unsigned int status;
status = UART_GET_STATUS(port);
/*
* Single IRQ for both Rx (data available) Tx (room available) Interrupt
* notifications from the UART Controller.
* To demultiplex between the two, we check the relevant bits
*/
if (status & RXIENB) {
/* already in ISR, no need of xx_irqsave */
spin_lock(&port->lock);
arc_serial_rx_chars(port, status);
spin_unlock(&port->lock);
}
if ((status & TXIENB) && (status & TXEMPTY)) {
/* Unconditionally disable further Tx-Interrupts.
* will be enabled by tx_chars() if needed.
*/
UART_TX_IRQ_DISABLE(port);
spin_lock(&port->lock);
if (!uart_tx_stopped(port))
arc_serial_tx_chars(port);
spin_unlock(&port->lock);
}
return IRQ_HANDLED;
}
static unsigned int arc_serial_get_mctrl(struct uart_port *port)
{
/*
* Pretend we have a Modem status reg and following bits are
* always set, to satify the serial core state machine
* (DSR) Data Set Ready
* (CTS) Clear To Send
* (CAR) Carrier Detect
*/
return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
}
static void arc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
/* MCR not present */
}
static void arc_serial_break_ctl(struct uart_port *port, int break_state)
{
/* ARC UART doesn't support sending Break signal */
}
static int arc_serial_startup(struct uart_port *port)
{
/* Before we hook up the ISR, Disable all UART Interrupts */
UART_ALL_IRQ_DISABLE(port);
if (request_irq(port->irq, arc_serial_isr, 0, "arc uart rx-tx", port)) {
dev_warn(port->dev, "Unable to attach ARC UART intr\n");
return -EBUSY;
}
UART_RX_IRQ_ENABLE(port); /* Only Rx IRQ enabled to begin with */
return 0;
}
/* This is not really needed */
static void arc_serial_shutdown(struct uart_port *port)
{
free_irq(port->irq, port);
}
static void
arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
struct ktermios *old)
{
struct arc_uart_port *uart = to_arc_port(port);
unsigned int baud, uartl, uarth, hw_val;
unsigned long flags;
/*
* Use the generic handler so that any specially encoded baud rates
* such as SPD_xx flags or "%B0" can be handled
* Max Baud I suppose will not be more than current 115K * 4
* Formula for ARC UART is: hw-val = ((CLK/(BAUD*4)) -1)
* spread over two 8-bit registers
*/
baud = uart_get_baud_rate(port, new, old, 0, 460800);
hw_val = port->uartclk / (uart->baud * 4) - 1;
uartl = hw_val & 0xFF;
uarth = (hw_val >> 8) & 0xFF;
spin_lock_irqsave(&port->lock, flags);
UART_ALL_IRQ_DISABLE(port);
UART_SET_BAUDL(port, uartl);
UART_SET_BAUDH(port, uarth);
UART_RX_IRQ_ENABLE(port);
/*
* UART doesn't support Parity/Hardware Flow Control;
* Only supports 8N1 character size
*/
new->c_cflag &= ~(CMSPAR|CRTSCTS|CSIZE);
new->c_cflag |= CS8;
if (old)
tty_termios_copy_hw(new, old);
/* Don't rewrite B0 */
if (tty_termios_baud_rate(new))
tty_termios_encode_baud_rate(new, baud, baud);
uart_update_timeout(port, new->c_cflag, baud);
spin_unlock_irqrestore(&port->lock, flags);
}
static const char *arc_serial_type(struct uart_port *port)
{
return port->type == PORT_ARC ? DRIVER_NAME : NULL;
}
static void arc_serial_release_port(struct uart_port *port)
{
}
static int arc_serial_request_port(struct uart_port *port)
{
return 0;
}
/*
* Verify the new serial_struct (for TIOCSSERIAL).
*/
static int
arc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
{
if (port->type != PORT_UNKNOWN && ser->type != PORT_ARC)
return -EINVAL;
return 0;
}
/*
* Configure/autoconfigure the port.
*/
static void arc_serial_config_port(struct uart_port *port, int flags)
{
if (flags & UART_CONFIG_TYPE)
port->type = PORT_ARC;
}
#ifdef CONFIG_CONSOLE_POLL
static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
{
while (!(UART_GET_STATUS(port) & TXEMPTY))
cpu_relax();
UART_SET_DATA(port, chr);
}
static int arc_serial_poll_getchar(struct uart_port *port)
{
unsigned char chr;
while (!(UART_GET_STATUS(port) & RXEMPTY))
cpu_relax();
chr = UART_GET_DATA(port);
return chr;
}
#endif
static const struct uart_ops arc_serial_pops = {
.tx_empty = arc_serial_tx_empty,
.set_mctrl = arc_serial_set_mctrl,
.get_mctrl = arc_serial_get_mctrl,
.stop_tx = arc_serial_stop_tx,
.start_tx = arc_serial_start_tx,
.stop_rx = arc_serial_stop_rx,
.break_ctl = arc_serial_break_ctl,
.startup = arc_serial_startup,
.shutdown = arc_serial_shutdown,
.set_termios = arc_serial_set_termios,
.type = arc_serial_type,
.release_port = arc_serial_release_port,
.request_port = arc_serial_request_port,
.config_port = arc_serial_config_port,
.verify_port = arc_serial_verify_port,
#ifdef CONFIG_CONSOLE_POLL
.poll_put_char = arc_serial_poll_putchar,
.poll_get_char = arc_serial_poll_getchar,
#endif
};
#ifdef CONFIG_SERIAL_ARC_CONSOLE
static int arc_serial_console_setup(struct console *co, char *options)
{
struct uart_port *port;
int baud = 115200;
int bits = 8;
int parity = 'n';
int flow = 'n';
if (co->index < 0 || co->index >= CONFIG_SERIAL_ARC_NR_PORTS)
return -ENODEV;
/*
* The uart port backing the console (e.g. ttyARC1) might not have been
* init yet. If so, defer the console setup to after the port.
*/
port = &arc_uart_ports[co->index].port;
if (!port->membase)
return -ENODEV;
if (options)
uart_parse_options(options, &baud, &parity, &bits, &flow);
/*
* Serial core will call port->ops->set_termios( )
* which will set the baud reg
*/
return uart_set_options(port, co, baud, parity, bits, flow);
}
static void arc_serial_console_putchar(struct uart_port *port, int ch)
{
while (!(UART_GET_STATUS(port) & TXEMPTY))
cpu_relax();
UART_SET_DATA(port, (unsigned char)ch);
}
/*
* Interrupts are disabled on entering
*/
static void arc_serial_console_write(struct console *co, const char *s,
unsigned int count)
{
struct uart_port *port = &arc_uart_ports[co->index].port;
unsigned long flags;
spin_lock_irqsave(&port->lock, flags);
uart_console_write(port, s, count, arc_serial_console_putchar);
spin_unlock_irqrestore(&port->lock, flags);
}
static struct console arc_console = {
.name = ARC_SERIAL_DEV_NAME,
.write = arc_serial_console_write,
.device = uart_console_device,
.setup = arc_serial_console_setup,
.flags = CON_PRINTBUFFER,
.index = -1,
.data = &arc_uart_driver
};
static void arc_early_serial_write(struct console *con, const char *s,
unsigned int n)
{
struct earlycon_device *dev = con->data;
uart_console_write(&dev->port, s, n, arc_serial_console_putchar);
}
static int __init arc_early_console_setup(struct earlycon_device *dev,
const char *opt)
{
struct uart_port *port = &dev->port;
unsigned int l, h, hw_val;
if (!dev->port.membase)
return -ENODEV;
hw_val = port->uartclk / (dev->baud * 4) - 1;
l = hw_val & 0xFF;
h = (hw_val >> 8) & 0xFF;
UART_SET_BAUDL(port, l);
UART_SET_BAUDH(port, h);
dev->con->write = arc_early_serial_write;
return 0;
}
OF_EARLYCON_DECLARE(arc_uart, "snps,arc-uart", arc_early_console_setup);
#endif /* CONFIG_SERIAL_ARC_CONSOLE */
static int arc_serial_probe(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node;
struct arc_uart_port *uart;
struct uart_port *port;
int dev_id;
u32 val;
/* no device tree device */
if (!np)
return -ENODEV;
dev_id = of_alias_get_id(np, "serial");
if (dev_id < 0)
dev_id = 0;
if (dev_id >= ARRAY_SIZE(arc_uart_ports)) {
dev_err(&pdev->dev, "serial%d out of range\n", dev_id);
return -EINVAL;
}
uart = &arc_uart_ports[dev_id];
port = &uart->port;
if (of_property_read_u32(np, "clock-frequency", &val)) {
dev_err(&pdev->dev, "clock-frequency property NOTset\n");
return -EINVAL;
}
port->uartclk = val;
if (of_property_read_u32(np, "current-speed", &val)) {
dev_err(&pdev->dev, "current-speed property NOT set\n");
return -EINVAL;
}
uart->baud = val;
port->membase = of_iomap(np, 0);
if (!port->membase)
/* No point of dev_err since UART itself is hosed here */
return -ENXIO;
port->irq = irq_of_parse_and_map(np, 0);
port->dev = &pdev->dev;
port->iotype = UPIO_MEM;
port->flags = UPF_BOOT_AUTOCONF;
port->line = dev_id;
port->ops = &arc_serial_pops;
port->fifosize = ARC_UART_TX_FIFO_SIZE;
/*
* uart_insert_char( ) uses it in decideding whether to ignore a
* char or not. Explicitly setting it here, removes the subtelty
*/
port->ignore_status_mask = 0;
return uart_add_one_port(&arc_uart_driver, &arc_uart_ports[dev_id].port);
}
static int arc_serial_remove(struct platform_device *pdev)
{
/* This will never be called */
return 0;
}
static const struct of_device_id arc_uart_dt_ids[] = {
{ .compatible = "snps,arc-uart" },
{ /* Sentinel */ }
};
MODULE_DEVICE_TABLE(of, arc_uart_dt_ids);
static struct platform_driver arc_platform_driver = {
.probe = arc_serial_probe,
.remove = arc_serial_remove,
.driver = {
.name = DRIVER_NAME,
.of_match_table = arc_uart_dt_ids,
},
};
static int __init arc_serial_init(void)
{
int ret;
ret = uart_register_driver(&arc_uart_driver);
if (ret)
return ret;
ret = platform_driver_register(&arc_platform_driver);
if (ret)
uart_unregister_driver(&arc_uart_driver);
return ret;
}
static void __exit arc_serial_exit(void)
{
platform_driver_unregister(&arc_platform_driver);
uart_unregister_driver(&arc_uart_driver);
}
module_init(arc_serial_init);
module_exit(arc_serial_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRIVER_NAME);
MODULE_AUTHOR("Vineet Gupta");
MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");