SERIAL: AR933X: Add driver for the built-in UART of the SoC

This patch adds the driver for the built-in UART of the
Atheros AR933X SoCs.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: Kathy Giori <kgiori@qca.qualcomm.com>
Cc: "Luis R.  Rodriguez" <rodrigue@qca.qualcomm.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-serial@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/2526/
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 688 insertions, 0 deletions

diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
new file mode 100644
index 000000000000..e4f60e2b87f3
--- /dev/null
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -0,0 +1,688 @@
+/*
+ *  Atheros AR933X SoC built-in UART driver
+ *
+ *  Copyright (C) 2011 Gabor Juhos <juhosg@openwrt.org>
+ *
+ *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
+ *
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/sysrq.h>
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial_core.h>
+#include <linux/serial.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+
+#include <asm/mach-ath79/ar933x_uart.h>
+#include <asm/mach-ath79/ar933x_uart_platform.h>
+
+#define DRIVER_NAME "ar933x-uart"
+
+#define AR933X_DUMMY_STATUS_RD	0x01
+
+static struct uart_driver ar933x_uart_driver;
+
+struct ar933x_uart_port {
+	struct uart_port	port;
+	unsigned int		ier;	/* shadow Interrupt Enable Register */
+};
+
+static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
+					    int offset)
+{
+	return readl(up->port.membase + offset);
+}
+
+static inline void ar933x_uart_write(struct ar933x_uart_port *up,
+				     int offset, unsigned int value)
+{
+	writel(value, up->port.membase + offset);
+}
+
+static inline void ar933x_uart_rmw(struct ar933x_uart_port *up,
+				  unsigned int offset,
+				  unsigned int mask,
+				  unsigned int val)
+{
+	unsigned int t;
+
+	t = ar933x_uart_read(up, offset);
+	t &= ~mask;
+	t |= val;
+	ar933x_uart_write(up, offset, t);
+}
+
+static inline void ar933x_uart_rmw_set(struct ar933x_uart_port *up,
+				       unsigned int offset,
+				       unsigned int val)
+{
+	ar933x_uart_rmw(up, offset, 0, val);
+}
+
+static inline void ar933x_uart_rmw_clear(struct ar933x_uart_port *up,
+					 unsigned int offset,
+					 unsigned int val)
+{
+	ar933x_uart_rmw(up, offset, val, 0);
+}
+
+static inline void ar933x_uart_start_tx_interrupt(struct ar933x_uart_port *up)
+{
+	up->ier |= AR933X_UART_INT_TX_EMPTY;
+	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
+static inline void ar933x_uart_stop_tx_interrupt(struct ar933x_uart_port *up)
+{
+	up->ier &= ~AR933X_UART_INT_TX_EMPTY;
+	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
+static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
+{
+	unsigned int rdata;
+
+	rdata = ch & AR933X_UART_DATA_TX_RX_MASK;
+	rdata |= AR933X_UART_DATA_TX_CSR;
+	ar933x_uart_write(up, AR933X_UART_DATA_REG, rdata);
+}
+
+static unsigned int ar933x_uart_tx_empty(struct uart_port *port)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+	unsigned long flags;
+	unsigned int rdata;
+
+	spin_lock_irqsave(&up->port.lock, flags);
+	rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+	spin_unlock_irqrestore(&up->port.lock, flags);
+
+	return (rdata & AR933X_UART_DATA_TX_CSR) ? 0 : TIOCSER_TEMT;
+}
+
+static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_CAR;
+}
+
+static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+}
+
+static void ar933x_uart_start_tx(struct uart_port *port)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+	ar933x_uart_start_tx_interrupt(up);
+}
+
+static void ar933x_uart_stop_tx(struct uart_port *port)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+	ar933x_uart_stop_tx_interrupt(up);
+}
+
+static void ar933x_uart_stop_rx(struct uart_port *port)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+	up->ier &= ~AR933X_UART_INT_RX_VALID;
+	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+}
+
+static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+	unsigned long flags;
+
+	spin_lock_irqsave(&up->port.lock, flags);
+	if (break_state == -1)
+		ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
+				    AR933X_UART_CS_TX_BREAK);
+	else
+		ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
+				      AR933X_UART_CS_TX_BREAK);
+	spin_unlock_irqrestore(&up->port.lock, flags);
+}
+
+static void ar933x_uart_enable_ms(struct uart_port *port)
+{
+}
+
+static void ar933x_uart_set_termios(struct uart_port *port,
+				    struct ktermios *new,
+				    struct ktermios *old)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+	unsigned int cs;
+	unsigned long flags;
+	unsigned int baud, scale;
+
+	/* Only CS8 is supported */
+	new->c_cflag &= ~CSIZE;
+	new->c_cflag |= CS8;
+
+	/* Only one stop bit is supported */
+	new->c_cflag &= ~CSTOPB;
+
+	cs = 0;
+	if (new->c_cflag & PARENB) {
+		if (!(new->c_cflag & PARODD))
+			cs |= AR933X_UART_CS_PARITY_EVEN;
+		else
+			cs |= AR933X_UART_CS_PARITY_ODD;
+	} else {
+		cs |= AR933X_UART_CS_PARITY_NONE;
+	}
+
+	/* Mark/space parity is not supported */
+	new->c_cflag &= ~CMSPAR;
+
+	baud = uart_get_baud_rate(port, new, old, 0, port->uartclk / 16);
+	scale = (port->uartclk / (16 * baud)) - 1;
+
+	/*
+	 * Ok, we're now changing the port state. Do it with
+	 * interrupts disabled.
+	 */
+	spin_lock_irqsave(&up->port.lock, flags);
+
+	/* Update the per-port timeout. */
+	uart_update_timeout(port, new->c_cflag, baud);
+
+	up->port.ignore_status_mask = 0;
+
+	/* ignore all characters if CREAD is not set */
+	if ((new->c_cflag & CREAD) == 0)
+		up->port.ignore_status_mask |= AR933X_DUMMY_STATUS_RD;
+
+	ar933x_uart_write(up, AR933X_UART_CLOCK_REG,
+			  scale << AR933X_UART_CLOCK_SCALE_S | 8192);
+
+	/* setup configuration register */
+	ar933x_uart_rmw(up, AR933X_UART_CS_REG, AR933X_UART_CS_PARITY_M, cs);
+
+	/* enable host interrupt */
+	ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
+			    AR933X_UART_CS_HOST_INT_EN);
+
+	spin_unlock_irqrestore(&up->port.lock, flags);
+
+	if (tty_termios_baud_rate(new))
+		tty_termios_encode_baud_rate(new, baud, baud);
+}
+
+static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
+{
+	struct tty_struct *tty;
+	int max_count = 256;
+
+	tty = tty_port_tty_get(&up->port.state->port);
+	do {
+		unsigned int rdata;
+		unsigned char ch;
+
+		rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+		if ((rdata & AR933X_UART_DATA_RX_CSR) == 0)
+			break;
+
+		/* remove the character from the FIFO */
+		ar933x_uart_write(up, AR933X_UART_DATA_REG,
+				  AR933X_UART_DATA_RX_CSR);
+
+		if (!tty) {
+			/* discard the data if no tty available */
+			continue;
+		}
+
+		up->port.icount.rx++;
+		ch = rdata & AR933X_UART_DATA_TX_RX_MASK;
+
+		if (uart_handle_sysrq_char(&up->port, ch))
+			continue;
+
+		if ((up->port.ignore_status_mask & AR933X_DUMMY_STATUS_RD) == 0)
+			tty_insert_flip_char(tty, ch, TTY_NORMAL);
+	} while (max_count-- > 0);
+
+	if (tty) {
+		tty_flip_buffer_push(tty);
+		tty_kref_put(tty);
+	}
+}
+
+static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
+{
+	struct circ_buf *xmit = &up->port.state->xmit;
+	int count;
+
+	if (uart_tx_stopped(&up->port))
+		return;
+
+	count = up->port.fifosize;
+	do {
+		unsigned int rdata;
+
+		rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+		if ((rdata & AR933X_UART_DATA_TX_CSR) == 0)
+			break;
+
+		if (up->port.x_char) {
+			ar933x_uart_putc(up, up->port.x_char);
+			up->port.icount.tx++;
+			up->port.x_char = 0;
+			continue;
+		}
+
+		if (uart_circ_empty(xmit))
+			break;
+
+		ar933x_uart_putc(up, xmit->buf[xmit->tail]);
+
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		up->port.icount.tx++;
+	} while (--count > 0);
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&up->port);
+
+	if (!uart_circ_empty(xmit))
+		ar933x_uart_start_tx_interrupt(up);
+}
+
+static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
+{
+	struct ar933x_uart_port *up = dev_id;
+	unsigned int status;
+
+	status = ar933x_uart_read(up, AR933X_UART_CS_REG);
+	if ((status & AR933X_UART_CS_HOST_INT) == 0)
+		return IRQ_NONE;
+
+	spin_lock(&up->port.lock);
+
+	status = ar933x_uart_read(up, AR933X_UART_INT_REG);
+	status &= ar933x_uart_read(up, AR933X_UART_INT_EN_REG);
+
+	if (status & AR933X_UART_INT_RX_VALID) {
+		ar933x_uart_write(up, AR933X_UART_INT_REG,
+				  AR933X_UART_INT_RX_VALID);
+		ar933x_uart_rx_chars(up);
+	}
+
+	if (status & AR933X_UART_INT_TX_EMPTY) {
+		ar933x_uart_write(up, AR933X_UART_INT_REG,
+				  AR933X_UART_INT_TX_EMPTY);
+		ar933x_uart_stop_tx_interrupt(up);
+		ar933x_uart_tx_chars(up);
+	}
+
+	spin_unlock(&up->port.lock);
+
+	return IRQ_HANDLED;
+}
+
+static int ar933x_uart_startup(struct uart_port *port)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+	unsigned long flags;
+	int ret;
+
+	ret = request_irq(up->port.irq, ar933x_uart_interrupt,
+			  up->port.irqflags, dev_name(up->port.dev), up);
+	if (ret)
+		return ret;
+
+	spin_lock_irqsave(&up->port.lock, flags);
+
+	/* Enable HOST interrupts */
+	ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
+			    AR933X_UART_CS_HOST_INT_EN);
+
+	/* Enable RX interrupts */
+	up->ier = AR933X_UART_INT_RX_VALID;
+	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+
+	spin_unlock_irqrestore(&up->port.lock, flags);
+
+	return 0;
+}
+
+static void ar933x_uart_shutdown(struct uart_port *port)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+	/* Disable all interrupts */
+	up->ier = 0;
+	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
+
+	/* Disable break condition */
+	ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
+			      AR933X_UART_CS_TX_BREAK);
+
+	free_irq(up->port.irq, up);
+}
+
+static const char *ar933x_uart_type(struct uart_port *port)
+{
+	return (port->type == PORT_AR933X) ? "AR933X UART" : NULL;
+}
+
+static void ar933x_uart_release_port(struct uart_port *port)
+{
+	/* Nothing to release ... */
+}
+
+static int ar933x_uart_request_port(struct uart_port *port)
+{
+	/* UARTs always present */
+	return 0;
+}
+
+static void ar933x_uart_config_port(struct uart_port *port, int flags)
+{
+	if (flags & UART_CONFIG_TYPE)
+		port->type = PORT_AR933X;
+}
+
+static int ar933x_uart_verify_port(struct uart_port *port,
+				   struct serial_struct *ser)
+{
+	if (ser->type != PORT_UNKNOWN &&
+	    ser->type != PORT_AR933X)
+		return -EINVAL;
+
+	if (ser->irq < 0 || ser->irq >= NR_IRQS)
+		return -EINVAL;
+
+	if (ser->baud_base < 28800)
+		return -EINVAL;
+
+	return 0;
+}
+
+static struct uart_ops ar933x_uart_ops = {
+	.tx_empty	= ar933x_uart_tx_empty,
+	.set_mctrl	= ar933x_uart_set_mctrl,
+	.get_mctrl	= ar933x_uart_get_mctrl,
+	.stop_tx	= ar933x_uart_stop_tx,
+	.start_tx	= ar933x_uart_start_tx,
+	.stop_rx	= ar933x_uart_stop_rx,
+	.enable_ms	= ar933x_uart_enable_ms,
+	.break_ctl	= ar933x_uart_break_ctl,
+	.startup	= ar933x_uart_startup,
+	.shutdown	= ar933x_uart_shutdown,
+	.set_termios	= ar933x_uart_set_termios,
+	.type		= ar933x_uart_type,
+	.release_port	= ar933x_uart_release_port,
+	.request_port	= ar933x_uart_request_port,
+	.config_port	= ar933x_uart_config_port,
+	.verify_port	= ar933x_uart_verify_port,
+};
+
+#ifdef CONFIG_SERIAL_AR933X_CONSOLE
+
+static struct ar933x_uart_port *
+ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
+
+static void ar933x_uart_wait_xmitr(struct ar933x_uart_port *up)
+{
+	unsigned int status;
+	unsigned int timeout = 60000;
+
+	/* Wait up to 60ms for the character(s) to be sent. */
+	do {
+		status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
+		if (--timeout == 0)
+			break;
+		udelay(1);
+	} while ((status & AR933X_UART_DATA_TX_CSR) == 0);
+}
+
+static void ar933x_uart_console_putchar(struct uart_port *port, int ch)
+{
+	struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+
+	ar933x_uart_wait_xmitr(up);
+	ar933x_uart_putc(up, ch);
+}
+
+static void ar933x_uart_console_write(struct console *co, const char *s,
+				      unsigned int count)
+{
+	struct ar933x_uart_port *up = ar933x_console_ports[co->index];
+	unsigned long flags;
+	unsigned int int_en;
+	int locked = 1;
+
+	local_irq_save(flags);
+
+	if (up->port.sysrq)
+		locked = 0;
+	else if (oops_in_progress)
+		locked = spin_trylock(&up->port.lock);
+	else
+		spin_lock(&up->port.lock);
+
+	/*
+	 * First save the IER then disable the interrupts
+	 */
+	int_en = ar933x_uart_read(up, AR933X_UART_INT_EN_REG);
+	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, 0);
+
+	uart_console_write(&up->port, s, count, ar933x_uart_console_putchar);
+
+	/*
+	 * Finally, wait for transmitter to become empty
+	 * and restore the IER
+	 */
+	ar933x_uart_wait_xmitr(up);
+	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, int_en);
+
+	ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_ALLINTS);
+
+	if (locked)
+		spin_unlock(&up->port.lock);
+
+	local_irq_restore(flags);
+}
+
+static int ar933x_uart_console_setup(struct console *co, char *options)
+{
+	struct ar933x_uart_port *up;
+	int baud = 115200;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	if (co->index < 0 || co->index >= CONFIG_SERIAL_AR933X_NR_UARTS)
+		return -EINVAL;
+
+	up = ar933x_console_ports[co->index];
+	if (!up)
+		return -ENODEV;
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	return uart_set_options(&up->port, co, baud, parity, bits, flow);
+}
+
+static struct console ar933x_uart_console = {
+	.name		= "ttyATH",
+	.write		= ar933x_uart_console_write,
+	.device		= uart_console_device,
+	.setup		= ar933x_uart_console_setup,
+	.flags		= CON_PRINTBUFFER,
+	.index		= -1,
+	.data		= &ar933x_uart_driver,
+};
+
+static void ar933x_uart_add_console_port(struct ar933x_uart_port *up)
+{
+	ar933x_console_ports[up->port.line] = up;
+}
+
+#define AR933X_SERIAL_CONSOLE	(&ar933x_uart_console)
+
+#else
+
+static inline void ar933x_uart_add_console_port(struct ar933x_uart_port *up) {}
+
+#define AR933X_SERIAL_CONSOLE	NULL
+
+#endif /* CONFIG_SERIAL_AR933X_CONSOLE */
+
+static struct uart_driver ar933x_uart_driver = {
+	.owner		= THIS_MODULE,
+	.driver_name	= DRIVER_NAME,
+	.dev_name	= "ttyATH",
+	.nr		= CONFIG_SERIAL_AR933X_NR_UARTS,
+	.cons		= AR933X_SERIAL_CONSOLE,
+};
+
+static int __devinit ar933x_uart_probe(struct platform_device *pdev)
+{
+	struct ar933x_uart_platform_data *pdata;
+	struct ar933x_uart_port *up;
+	struct uart_port *port;
+	struct resource *mem_res;
+	struct resource *irq_res;
+	int id;
+	int ret;
+
+	pdata = pdev->dev.platform_data;
+	if (!pdata)
+		return -EINVAL;
+
+	id = pdev->id;
+	if (id == -1)
+		id = 0;
+
+	if (id > CONFIG_SERIAL_AR933X_NR_UARTS)
+		return -EINVAL;
+
+	mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!mem_res) {
+		dev_err(&pdev->dev, "no MEM resource\n");
+		return -EINVAL;
+	}
+
+	irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!irq_res) {
+		dev_err(&pdev->dev, "no IRQ resource\n");
+		return -EINVAL;
+	}
+
+	up = kzalloc(sizeof(struct ar933x_uart_port), GFP_KERNEL);
+	if (!up)
+		return -ENOMEM;
+
+	port = &up->port;
+	port->mapbase = mem_res->start;
+
+	port->membase = ioremap(mem_res->start, AR933X_UART_REGS_SIZE);
+	if (!port->membase) {
+		ret = -ENOMEM;
+		goto err_free_up;
+	}
+
+	port->line = id;
+	port->irq = irq_res->start;
+	port->dev = &pdev->dev;
+	port->type = PORT_AR933X;
+	port->iotype = UPIO_MEM32;
+	port->uartclk = pdata->uartclk;
+
+	port->regshift = 2;
+	port->fifosize = AR933X_UART_FIFO_SIZE;
+	port->ops = &ar933x_uart_ops;
+
+	ar933x_uart_add_console_port(up);
+
+	ret = uart_add_one_port(&ar933x_uart_driver, &up->port);
+	if (ret)
+		goto err_unmap;
+
+	platform_set_drvdata(pdev, up);
+	return 0;
+
+err_unmap:
+	iounmap(up->port.membase);
+err_free_up:
+	kfree(up);
+	return ret;
+}
+
+static int __devexit ar933x_uart_remove(struct platform_device *pdev)
+{
+	struct ar933x_uart_port *up;
+
+	up = platform_get_drvdata(pdev);
+	platform_set_drvdata(pdev, NULL);
+
+	if (up) {
+		uart_remove_one_port(&ar933x_uart_driver, &up->port);
+		iounmap(up->port.membase);
+		kfree(up);
+	}
+
+	return 0;
+}
+
+static struct platform_driver ar933x_uart_platform_driver = {
+	.probe		= ar933x_uart_probe,
+	.remove		= __devexit_p(ar933x_uart_remove),
+	.driver		= {
+		.name		= DRIVER_NAME,
+		.owner		= THIS_MODULE,
+	},
+};
+
+static int __init ar933x_uart_init(void)
+{
+	int ret;
+
+	ar933x_uart_driver.nr = CONFIG_SERIAL_AR933X_NR_UARTS;
+	ret = uart_register_driver(&ar933x_uart_driver);
+	if (ret)
+		goto err_out;
+
+	ret = platform_driver_register(&ar933x_uart_platform_driver);
+	if (ret)
+		goto err_unregister_uart_driver;
+
+	return 0;
+
+err_unregister_uart_driver:
+	uart_unregister_driver(&ar933x_uart_driver);
+err_out:
+	return ret;
+}
+
+static void __exit ar933x_uart_exit(void)
+{
+	platform_driver_unregister(&ar933x_uart_platform_driver);
+	uart_unregister_driver(&ar933x_uart_driver);
+}
+
+module_init(ar933x_uart_init);
+module_exit(ar933x_uart_exit);
+
+MODULE_DESCRIPTION("Atheros AR933X UART driver");
+MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRIVER_NAME);