serial: mps2-uart: add MPS2 UART driver

This driver adds support to the UART controller found on ARM MPS2
platform.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 610 insertions, 0 deletions

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 9af489b0f388..3b0a9b3ec4e1 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1448,6 +1448,18 @@ config SERIAL_EFM32_UART
 	  This driver support the USART and UART ports on
 	  Energy Micro's efm32 SoCs.
 
+config SERIAL_MPS2_UART_CONSOLE
+	bool "MPS2 UART console support"
+	depends on SERIAL_MPS2_UART
+	select SERIAL_CORE_CONSOLE
+
+config SERIAL_MPS2_UART
+	bool "MPS2 UART port"
+	depends on ARM || COMPILE_TEST
+	select SERIAL_CORE
+	help
+	  This driver support the UART ports on ARM MPS2.
+
 config SERIAL_EFM32_UART_CONSOLE
 	bool "EFM32 UART/USART console support"
 	depends on SERIAL_EFM32_UART=y
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 8c261adac04e..81e9057a0f68 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -91,6 +91,7 @@ obj-$(CONFIG_SERIAL_MEN_Z135)	+= men_z135_uart.o
 obj-$(CONFIG_SERIAL_SPRD) += sprd_serial.o
 obj-$(CONFIG_SERIAL_STM32)	+= stm32-usart.o
 obj-$(CONFIG_SERIAL_MVEBU_UART)	+= mvebu-uart.o
+obj-$(CONFIG_SERIAL_MPS2_UART)	+= mps2-uart.o
 
 # GPIOLIB helpers for modem control lines
 obj-$(CONFIG_SERIAL_MCTRL_GPIO)	+= serial_mctrl_gpio.o
diff --git a/drivers/tty/serial/mps2-uart.c b/drivers/tty/serial/mps2-uart.c
new file mode 100644
index 000000000000..e571e4cdfab3
--- /dev/null
+++ b/drivers/tty/serial/mps2-uart.c
@@ -0,0 +1,597 @@
+/*
+ * Copyright (C) 2015 ARM Limited
+ *
+ * Author: Vladimir Murzin <vladimir.murzin@arm.com>
+ *
+ * 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.
+ *
+ * TODO: support for SysRq
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/console.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/serial_core.h>
+#include <linux/tty_flip.h>
+#include <linux/types.h>
+
+#define SERIAL_NAME	"ttyMPS"
+#define DRIVER_NAME	"mps2-uart"
+#define MAKE_NAME(x)	(DRIVER_NAME # x)
+
+#define UARTn_DATA				0x00
+
+#define UARTn_STATE				0x04
+#define UARTn_STATE_TX_FULL			BIT(0)
+#define UARTn_STATE_RX_FULL			BIT(1)
+#define UARTn_STATE_TX_OVERRUN			BIT(2)
+#define UARTn_STATE_RX_OVERRUN			BIT(3)
+
+#define UARTn_CTRL				0x08
+#define UARTn_CTRL_TX_ENABLE			BIT(0)
+#define UARTn_CTRL_RX_ENABLE			BIT(1)
+#define UARTn_CTRL_TX_INT_ENABLE		BIT(2)
+#define UARTn_CTRL_RX_INT_ENABLE		BIT(3)
+#define UARTn_CTRL_TX_OVERRUN_INT_ENABLE	BIT(4)
+#define UARTn_CTRL_RX_OVERRUN_INT_ENABLE	BIT(5)
+
+#define UARTn_INT				0x0c
+#define UARTn_INT_TX				BIT(0)
+#define UARTn_INT_RX				BIT(1)
+#define UARTn_INT_TX_OVERRUN			BIT(2)
+#define UARTn_INT_RX_OVERRUN			BIT(3)
+
+#define UARTn_BAUDDIV				0x10
+#define UARTn_BAUDDIV_MASK			GENMASK(20, 0)
+
+/*
+ * Helpers to make typical enable/disable operations more readable.
+ */
+#define UARTn_CTRL_TX_GRP	(UARTn_CTRL_TX_ENABLE		 |\
+				 UARTn_CTRL_TX_INT_ENABLE	 |\
+				 UARTn_CTRL_TX_OVERRUN_INT_ENABLE)
+
+#define UARTn_CTRL_RX_GRP	(UARTn_CTRL_RX_ENABLE		 |\
+				 UARTn_CTRL_RX_INT_ENABLE	 |\
+				 UARTn_CTRL_RX_OVERRUN_INT_ENABLE)
+
+#define MPS2_MAX_PORTS		3
+
+struct mps2_uart_port {
+	struct uart_port port;
+	struct clk *clk;
+	unsigned int tx_irq;
+	unsigned int rx_irq;
+};
+
+static inline struct mps2_uart_port *to_mps2_port(struct uart_port *port)
+{
+	return container_of(port, struct mps2_uart_port, port);
+}
+
+static void mps2_uart_write8(struct uart_port *port, u8 val, unsigned int off)
+{
+	struct mps2_uart_port *mps_port = to_mps2_port(port);
+
+	writeb(val, mps_port->port.membase + off);
+}
+
+static u8 mps2_uart_read8(struct uart_port *port, unsigned int off)
+{
+	struct mps2_uart_port *mps_port = to_mps2_port(port);
+
+	return readb(mps_port->port.membase + off);
+}
+
+static void mps2_uart_write32(struct uart_port *port, u32 val, unsigned int off)
+{
+	struct mps2_uart_port *mps_port = to_mps2_port(port);
+
+	writel_relaxed(val, mps_port->port.membase + off);
+}
+
+static unsigned int mps2_uart_tx_empty(struct uart_port *port)
+{
+	u8 status = mps2_uart_read8(port, UARTn_STATE);
+
+	return (status & UARTn_STATE_TX_FULL) ? 0 : TIOCSER_TEMT;
+}
+
+static void mps2_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+}
+
+static unsigned int mps2_uart_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_CAR | TIOCM_CTS | TIOCM_DSR;
+}
+
+static void mps2_uart_stop_tx(struct uart_port *port)
+{
+	u8 control = mps2_uart_read8(port, UARTn_CTRL);
+
+	control &= ~UARTn_CTRL_TX_INT_ENABLE;
+
+	mps2_uart_write8(port, control, UARTn_CTRL);
+}
+
+static void mps2_uart_tx_chars(struct uart_port *port)
+{
+	struct circ_buf *xmit = &port->state->xmit;
+
+	while (!(mps2_uart_read8(port, UARTn_STATE) & UARTn_STATE_TX_FULL)) {
+		if (port->x_char) {
+			mps2_uart_write8(port, port->x_char, UARTn_DATA);
+			port->x_char = 0;
+			port->icount.tx++;
+			continue;
+		}
+
+		if (uart_circ_empty(xmit) || uart_tx_stopped(port))
+			break;
+
+		mps2_uart_write8(port, xmit->buf[xmit->tail], UARTn_DATA);
+		xmit->tail = (xmit->tail + 1) % UART_XMIT_SIZE;
+		port->icount.tx++;
+	}
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
+
+	if (uart_circ_empty(xmit))
+		mps2_uart_stop_tx(port);
+}
+
+static void mps2_uart_start_tx(struct uart_port *port)
+{
+	u8 control = mps2_uart_read8(port, UARTn_CTRL);
+
+	control |= UARTn_CTRL_TX_INT_ENABLE;
+
+	mps2_uart_write8(port, control, UARTn_CTRL);
+
+	/*
+	 * We've just unmasked the TX IRQ and now slow-starting via
+	 * polling; if there is enough data to fill up the internal
+	 * write buffer in one go, the TX IRQ should assert, at which
+	 * point we switch to fully interrupt-driven TX.
+	 */
+
+	mps2_uart_tx_chars(port);
+}
+
+static void mps2_uart_stop_rx(struct uart_port *port)
+{
+	u8 control = mps2_uart_read8(port, UARTn_CTRL);
+
+	control &= ~UARTn_CTRL_RX_GRP;
+
+	mps2_uart_write8(port, control, UARTn_CTRL);
+}
+
+static void mps2_uart_break_ctl(struct uart_port *port, int ctl)
+{
+}
+
+static void mps2_uart_rx_chars(struct uart_port *port)
+{
+	struct tty_port *tport = &port->state->port;
+
+	while (mps2_uart_read8(port, UARTn_STATE) & UARTn_STATE_RX_FULL) {
+		u8 rxdata = mps2_uart_read8(port, UARTn_DATA);
+
+		port->icount.rx++;
+		tty_insert_flip_char(&port->state->port, rxdata, TTY_NORMAL);
+	}
+
+	tty_flip_buffer_push(tport);
+}
+
+static irqreturn_t mps2_uart_rxirq(int irq, void *data)
+{
+	struct uart_port *port = data;
+	u8 irqflag = mps2_uart_read8(port, UARTn_INT);
+
+	if (unlikely(!(irqflag & UARTn_INT_RX)))
+		return IRQ_NONE;
+
+	spin_lock(&port->lock);
+
+	mps2_uart_write8(port, UARTn_INT_RX, UARTn_INT);
+	mps2_uart_rx_chars(port);
+
+	spin_unlock(&port->lock);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t mps2_uart_txirq(int irq, void *data)
+{
+	struct uart_port *port = data;
+	u8 irqflag = mps2_uart_read8(port, UARTn_INT);
+
+	if (unlikely(!(irqflag & UARTn_INT_TX)))
+		return IRQ_NONE;
+
+	spin_lock(&port->lock);
+
+	mps2_uart_write8(port, UARTn_INT_TX, UARTn_INT);
+	mps2_uart_tx_chars(port);
+
+	spin_unlock(&port->lock);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t mps2_uart_oerrirq(int irq, void *data)
+{
+	irqreturn_t handled = IRQ_NONE;
+	struct uart_port *port = data;
+	u8 irqflag = mps2_uart_read8(port, UARTn_INT);
+
+	spin_lock(&port->lock);
+
+	if (irqflag & UARTn_INT_RX_OVERRUN) {
+		struct tty_port *tport = &port->state->port;
+
+		mps2_uart_write8(port, UARTn_INT_RX_OVERRUN, UARTn_INT);
+		port->icount.overrun++;
+		tty_insert_flip_char(tport, 0, TTY_OVERRUN);
+		tty_flip_buffer_push(tport);
+		handled = IRQ_HANDLED;
+	}
+
+	/*
+	 * It's never been seen in practice and it never *should* happen since
+	 * we check if there is enough room in TX buffer before sending data.
+	 * So we keep this check in case something suspicious has happened.
+	 */
+	if (irqflag & UARTn_INT_TX_OVERRUN) {
+		mps2_uart_write8(port, UARTn_INT_TX_OVERRUN, UARTn_INT);
+		handled = IRQ_HANDLED;
+	}
+
+	spin_unlock(&port->lock);
+
+	return handled;
+}
+
+static int mps2_uart_startup(struct uart_port *port)
+{
+	struct mps2_uart_port *mps_port = to_mps2_port(port);
+	u8 control = mps2_uart_read8(port, UARTn_CTRL);
+	int ret;
+
+	control &= ~(UARTn_CTRL_RX_GRP | UARTn_CTRL_TX_GRP);
+
+	mps2_uart_write8(port, control, UARTn_CTRL);
+
+	ret = request_irq(mps_port->rx_irq, mps2_uart_rxirq, 0,
+			  MAKE_NAME(-rx), mps_port);
+	if (ret) {
+		dev_err(port->dev, "failed to register rxirq (%d)\n", ret);
+		return ret;
+	}
+
+	ret = request_irq(mps_port->tx_irq, mps2_uart_txirq, 0,
+			  MAKE_NAME(-tx), mps_port);
+	if (ret) {
+		dev_err(port->dev, "failed to register txirq (%d)\n", ret);
+		goto err_free_rxirq;
+	}
+
+	ret = request_irq(port->irq, mps2_uart_oerrirq, IRQF_SHARED,
+			  MAKE_NAME(-overrun), mps_port);
+
+	if (ret) {
+		dev_err(port->dev, "failed to register oerrirq (%d)\n", ret);
+		goto err_free_txirq;
+	}
+
+	control |= UARTn_CTRL_RX_GRP | UARTn_CTRL_TX_GRP;
+
+	mps2_uart_write8(port, control, UARTn_CTRL);
+
+	return 0;
+
+err_free_txirq:
+	free_irq(mps_port->tx_irq, mps_port);
+err_free_rxirq:
+	free_irq(mps_port->rx_irq, mps_port);
+
+	return ret;
+}
+
+static void mps2_uart_shutdown(struct uart_port *port)
+{
+	struct mps2_uart_port *mps_port = to_mps2_port(port);
+	u8 control = mps2_uart_read8(port, UARTn_CTRL);
+
+	control &= ~(UARTn_CTRL_RX_GRP | UARTn_CTRL_TX_GRP);
+
+	mps2_uart_write8(port, control, UARTn_CTRL);
+
+	free_irq(mps_port->rx_irq, mps_port);
+	free_irq(mps_port->tx_irq, mps_port);
+	free_irq(port->irq, mps_port);
+}
+
+static void
+mps2_uart_set_termios(struct uart_port *port, struct ktermios *termios,
+		      struct ktermios *old)
+{
+	unsigned long flags;
+	unsigned int baud, bauddiv;
+
+	termios->c_cflag &= ~(CRTSCTS | CMSPAR);
+	termios->c_cflag &= ~CSIZE;
+	termios->c_cflag |= CS8;
+	termios->c_cflag &= ~PARENB;
+	termios->c_cflag &= ~CSTOPB;
+
+	baud = uart_get_baud_rate(port, termios, old,
+			DIV_ROUND_CLOSEST(port->uartclk, UARTn_BAUDDIV_MASK),
+			DIV_ROUND_CLOSEST(port->uartclk, 16));
+
+	bauddiv = DIV_ROUND_CLOSEST(port->uartclk, baud);
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	uart_update_timeout(port, termios->c_cflag, baud);
+	mps2_uart_write32(port, bauddiv, UARTn_BAUDDIV);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	if (tty_termios_baud_rate(termios))
+		tty_termios_encode_baud_rate(termios, baud, baud);
+}
+
+static const char *mps2_uart_type(struct uart_port *port)
+{
+	return (port->type == PORT_MPS2UART) ? DRIVER_NAME : NULL;
+}
+
+static void mps2_uart_release_port(struct uart_port *port)
+{
+}
+
+static int mps2_uart_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+static void mps2_uart_config_port(struct uart_port *port, int type)
+{
+	if (type & UART_CONFIG_TYPE && !mps2_uart_request_port(port))
+		port->type = PORT_MPS2UART;
+}
+
+static int mps2_uart_verify_port(struct uart_port *port, struct serial_struct *serinfo)
+{
+	return -EINVAL;
+}
+
+static const struct uart_ops mps2_uart_pops = {
+	.tx_empty = mps2_uart_tx_empty,
+	.set_mctrl = mps2_uart_set_mctrl,
+	.get_mctrl = mps2_uart_get_mctrl,
+	.stop_tx = mps2_uart_stop_tx,
+	.start_tx = mps2_uart_start_tx,
+	.stop_rx = mps2_uart_stop_rx,
+	.break_ctl = mps2_uart_break_ctl,
+	.startup = mps2_uart_startup,
+	.shutdown = mps2_uart_shutdown,
+	.set_termios = mps2_uart_set_termios,
+	.type = mps2_uart_type,
+	.release_port = mps2_uart_release_port,
+	.request_port = mps2_uart_request_port,
+	.config_port = mps2_uart_config_port,
+	.verify_port = mps2_uart_verify_port,
+};
+
+static struct mps2_uart_port mps2_uart_ports[MPS2_MAX_PORTS];
+
+#ifdef CONFIG_SERIAL_MPS2_UART_CONSOLE
+static void mps2_uart_console_putchar(struct uart_port *port, int ch)
+{
+	while (mps2_uart_read8(port, UARTn_STATE) & UARTn_STATE_TX_FULL)
+		cpu_relax();
+
+	mps2_uart_write8(port, ch, UARTn_DATA);
+}
+
+static void mps2_uart_console_write(struct console *co, const char *s, unsigned int cnt)
+{
+	struct uart_port *port = &mps2_uart_ports[co->index].port;
+
+	uart_console_write(port, s, cnt, mps2_uart_console_putchar);
+}
+
+static int mps2_uart_console_setup(struct console *co, char *options)
+{
+	struct mps2_uart_port *mps_port;
+	int baud = 9600;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	if (co->index < 0 || co->index >= MPS2_MAX_PORTS)
+		return -ENODEV;
+
+	mps_port = &mps2_uart_ports[co->index];
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	return uart_set_options(&mps_port->port, co, baud, parity, bits, flow);
+}
+
+static struct uart_driver mps2_uart_driver;
+
+static struct console mps2_uart_console = {
+	.name = SERIAL_NAME,
+	.device = uart_console_device,
+	.write = mps2_uart_console_write,
+	.setup = mps2_uart_console_setup,
+	.flags = CON_PRINTBUFFER,
+	.index = -1,
+	.data = &mps2_uart_driver,
+};
+
+#define MPS2_SERIAL_CONSOLE (&mps2_uart_console)
+
+#else
+#define MPS2_SERIAL_CONSOLE NULL
+#endif
+
+static struct uart_driver mps2_uart_driver = {
+	.driver_name = DRIVER_NAME,
+	.dev_name = SERIAL_NAME,
+	.nr = MPS2_MAX_PORTS,
+	.cons = MPS2_SERIAL_CONSOLE,
+};
+
+static struct mps2_uart_port *mps2_of_get_port(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	int id;
+
+	if (!np)
+		return NULL;
+
+	id = of_alias_get_id(np, "serial");
+	if (id < 0)
+		id = 0;
+
+	if (WARN_ON(id >= MPS2_MAX_PORTS))
+		return NULL;
+
+	mps2_uart_ports[id].port.line = id;
+	return &mps2_uart_ports[id];
+}
+
+static int mps2_init_port(struct mps2_uart_port *mps_port,
+			  struct platform_device *pdev)
+{
+	struct resource *res;
+	int ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	mps_port->port.membase = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(mps_port->port.membase))
+		return PTR_ERR(mps_port->port.membase);
+
+	mps_port->port.mapbase = res->start;
+	mps_port->port.mapsize = resource_size(res);
+
+	mps_port->rx_irq = platform_get_irq(pdev, 0);
+	mps_port->tx_irq = platform_get_irq(pdev, 1);
+	mps_port->port.irq = platform_get_irq(pdev, 2);
+
+	mps_port->port.iotype = UPIO_MEM;
+	mps_port->port.flags = UPF_BOOT_AUTOCONF;
+	mps_port->port.fifosize = 1;
+	mps_port->port.ops = &mps2_uart_pops;
+	mps_port->port.dev = &pdev->dev;
+
+	mps_port->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(mps_port->clk))
+		return PTR_ERR(mps_port->clk);
+
+	ret = clk_prepare_enable(mps_port->clk);
+	if (ret)
+		return ret;
+
+	mps_port->port.uartclk = clk_get_rate(mps_port->clk);
+
+	clk_disable_unprepare(mps_port->clk);
+
+	return ret;
+}
+
+static int mps2_serial_probe(struct platform_device *pdev)
+{
+	struct mps2_uart_port *mps_port;
+	int ret;
+
+	mps_port = mps2_of_get_port(pdev);
+	if (!mps_port)
+		return -ENODEV;
+
+	ret = mps2_init_port(mps_port, pdev);
+	if (ret)
+		return ret;
+
+	ret = uart_add_one_port(&mps2_uart_driver, &mps_port->port);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, mps_port);
+
+	return 0;
+}
+
+static int mps2_serial_remove(struct platform_device *pdev)
+{
+	struct mps2_uart_port *mps_port = platform_get_drvdata(pdev);
+
+	uart_remove_one_port(&mps2_uart_driver, &mps_port->port);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id mps2_match[] = {
+	{ .compatible = "arm,mps2-uart", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mps2_match);
+#endif
+
+static struct platform_driver mps2_serial_driver = {
+	.probe = mps2_serial_probe,
+	.remove = mps2_serial_remove,
+
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = of_match_ptr(mps2_match),
+	},
+};
+
+static int __init mps2_uart_init(void)
+{
+	int ret;
+
+	ret = uart_register_driver(&mps2_uart_driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&mps2_serial_driver);
+	if (ret)
+		uart_unregister_driver(&mps2_uart_driver);
+
+	return ret;
+}
+module_init(mps2_uart_init);
+
+static void __exit mps2_uart_exit(void)
+{
+	platform_driver_unregister(&mps2_serial_driver);
+	uart_unregister_driver(&mps2_uart_driver);
+}
+module_exit(mps2_uart_exit);
+
+MODULE_AUTHOR("Vladimir Murzin <vladimir.murzin@arm.com>");
+MODULE_DESCRIPTION("MPS2 UART driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRIVER_NAME);