[PATCH] serial/arc-uart: Add new driver

[PATCH] serial/arc-uart: Add new driver

[Vineet.Gupta1]

From: Vineet Gupta <vgupta@synopsys.com>

Driver for non-standard on-chip UART, instantiated in the ARC (Synopsys)
FPGA Boards such as ARCAngel4/ML50x

This is based off of current Linus tree, build tested for x86.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 drivers/tty/serial/Kconfig    |   25 ++
 drivers/tty/serial/Makefile   |    1 +
 drivers/tty/serial/arc_uart.c |  742 +++++++++++++++++++++++++++++++++++++++++
 include/linux/serial_core.h   |    3 +
 4 files changed, 771 insertions(+), 0 deletions(-)
 create mode 100644 drivers/tty/serial/arc_uart.c

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 4720b4b..af4bd69 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1360,4 +1360,29 @@ config SERIAL_EFM32_UART_CONSOLE
 	depends on SERIAL_EFM32_UART=y
 	select SERIAL_CORE_CONSOLE
 
+config SERIAL_ARC
+	bool "ARC UART driver support"
+	select SERIAL_CORE
+	default y
+	help
+	  Driver for on-chip UART for ARC(Synopsys) for the legacy
+	  FPGA Boards (ML50x/ARCAngel4)
+
+config SERIAL_ARC_CONSOLE
+	bool
+	select SERIAL_CORE_CONSOLE
+	depends on SERIAL_ARC=y
+	default y
+	help
+	  Enable system Console on ARC UART
+
+config SERIAL_ARC_NR_PORTS
+	int 'Number of ports'
+	range 1 3
+	default 1
+	depends on SERIAL_ARC
+	help
+	  Set this to the number of serial ports you want the driver
+	  to support.
+
 endmenu
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 7257c5d..2b70b5f 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -79,3 +79,4 @@ obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
 obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
 obj-$(CONFIG_SERIAL_AR933X)   += ar933x_uart.o
 obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
+obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
new file mode 100644
index 0000000..4f2e57b
--- /dev/null
+++ b/drivers/tty/serial/arc_uart.c
@@ -0,0 +1,742 @@
+/*
+ * ARC On-Chip(fpga) UART Driver
+ *
+ * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.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.
+ *
+ * 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>
+
+/*************************************
+ * 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	1
+#define R_ID2	2
+#define R_ID3	3
+#define R_DATA	4
+#define R_STS	5
+#define R_BAUDL	6
+#define R_BAUDH	7
+
+/* 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(uart, reg)      ((unsigned int *)uart->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	"ttyS"
+
+/* ttySxx per Documentation/devices.txt */
+#define ARC_SERIAL_MAJOR	4
+#define ARC_SERIAL_MINOR	64
+
+struct arc_uart_port {
+	struct uart_port port;
+	unsigned long baud;
+};
+
+static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+static struct console arc_serial_console;
+#define ARC_SERIAL_CONSOLE	(&arc_serial_console)
+#else
+#define ARC_SERIAL_CONSOLE	NULL
+#endif
+
+int __attribute__((weak)) running_on_iss;
+
+#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		= ARC_SERIAL_MAJOR,
+	.minor		= ARC_SERIAL_MINOR,
+	.nr		= CONFIG_SERIAL_ARC_NR_PORTS,
+	.cons		= ARC_SERIAL_CONSOLE,
+};
+
+static void arc_serial_stop_rx(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	UART_RX_IRQ_DISABLE(uart);
+}
+
+static void arc_serial_stop_tx(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	while (!(UART_GET_STATUS(uart) & TXEMPTY))
+		cpu_relax();
+
+	UART_TX_IRQ_DISABLE(uart);
+}
+
+/*
+ * Return TIOCSER_TEMT when transmitter is not busy.
+ */
+static unsigned int arc_serial_tx_empty(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+	unsigned int stat;
+
+	stat = UART_GET_STATUS(uart);
+	if (stat & TXEMPTY)
+		return TIOCSER_TEMT;
+	else
+		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 / tty->hw_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 arc_uart_port *uart)
+{
+	struct circ_buf *xmit = &uart->port.state->xmit;
+	int sent = 0;
+	unsigned char ch;
+
+	if (unlikely(uart->port.x_char)) {
+		UART_SET_DATA(uart, uart->port.x_char);
+		uart->port.icount.tx++;
+		uart->port.x_char = 0;
+		sent = 1;
+	} else if (xmit->tail != xmit->head) {	/* TODO: uart_circ_empty */
+		ch = xmit->buf[xmit->tail];
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		uart->port.icount.tx++;
+		while (!(UART_GET_STATUS(uart) & TXEMPTY))
+			cpu_relax();
+		UART_SET_DATA(uart, 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(&uart->port);
+
+	/*if (uart_circ_chars_pending(xmit)) */
+	if (sent)
+		UART_TX_IRQ_ENABLE(uart);
+
+}
+
+/*
+ * 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)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	arc_serial_tx_chars(uart);
+}
+
+static void arc_serial_rx_chars(struct arc_uart_port *uart)
+{
+	struct tty_struct *tty = NULL;
+	unsigned int status, ch, flg = 0;
+
+	tty = uart->port.state->port.tty;
+
+	/*
+	 * 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.
+	 */
+	while (!((status = UART_GET_STATUS(uart)) & RXEMPTY)) {
+
+		ch = UART_GET_DATA(uart);
+		uart->port.icount.rx++;
+
+		if (unlikely(status & (RXOERR | RXFERR))) {
+			if (status & RXOERR) {
+				uart->port.icount.overrun++;
+				flg = TTY_OVERRUN;
+				UART_CLR_STATUS(uart, RXOERR);
+			}
+
+			if (status & RXFERR) {
+				uart->port.icount.frame++;
+				flg = TTY_FRAME;
+				UART_CLR_STATUS(uart, RXFERR);
+			}
+		} else
+			flg = TTY_NORMAL;
+
+		if (unlikely(uart_handle_sysrq_char(&uart->port, ch)))
+			goto done;
+
+		uart_insert_char(&uart->port, status, RXOERR, ch, flg);
+
+done:
+		tty_flip_buffer_push(tty);
+	}
+}
+
+/*
+ * 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 arc_uart_port *uart = dev_id;
+	unsigned int status;
+
+	status = UART_GET_STATUS(uart);
+
+	/*
+	 * 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) && !(status & RXEMPTY)) {
+
+		/* already in ISR, no need of xx_irqsave */
+		spin_lock(&uart->port.lock);
+		arc_serial_rx_chars(uart);
+		spin_unlock(&uart->port.lock);
+	}
+
+	if ((status & TXIENB) && (status & TXEMPTY)) {
+
+		/* Unconditionally disable further Tx-Interrupts.
+		 * will be enabled by tx_chars() if needed.
+		 */
+		UART_TX_IRQ_DISABLE(uart);
+
+		spin_lock(&uart->port.lock);
+
+		if (!uart_tx_stopped(&uart->port))
+			arc_serial_tx_chars(uart);
+
+		spin_unlock(&uart->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 */
+}
+
+/* Enable Modem Status Interrupts */
+
+static void arc_serial_enable_ms(struct uart_port *port)
+{
+	/* MSR not present */
+}
+
+static void arc_serial_break_ctl(struct uart_port *port, int break_state)
+{
+	/* ARC UART doesn't support sendind Break signal */
+}
+
+static int arc_serial_startup(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	/* Before we hook up the ISR, Disable all UART Interrupts */
+	UART_ALL_IRQ_DISABLE(uart);
+
+	if (request_irq(uart->port.irq, arc_serial_isr, 0, "arc uart rx-tx",
+			uart)) {
+		pr_warn("Unable to attach ARC UART interrupt\n");
+		return -EBUSY;
+	}
+
+	UART_RX_IRQ_ENABLE(uart); /* Only Rx IRQ enabled to begin with */
+
+	return 0;
+}
+
+/* This is not really needed */
+static void arc_serial_shutdown(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+	free_irq(uart->port.irq, uart);
+}
+
+static void arc_serial_set_ldisc(struct uart_port *port, int ld)
+{
+	/* this might need implementing for the touch driver */
+}
+
+static void
+arc_serial_set_termios(struct uart_port *port, struct ktermios *termios,
+		       struct ktermios *old)
+{
+	struct arc_uart_port *uart = (struct arc_uart_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, termios, old, 0, 460800);
+
+	hw_val = port->uartclk / (uart->baud * 4) - 1;
+	uartl = hw_val & 0xFF;
+	uarth = (hw_val >> 8) & 0xFF;
+
+	/*
+	 * ISS UART emulation has a subtle bug:
+	 * A existing value of Baudh = 0 is used as a indication to startup
+	 * it's internal state machine.
+	 * Thus if baudh is set to 0, 2 times, it chokes.
+	 * This happens with BAUD=115200 and the formaula above
+	 * Until that is fixed, when running on ISS, we will set baudh to !0
+	 */
+	if (running_on_iss)
+		uarth = 1;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	UART_ALL_IRQ_DISABLE(uart);
+
+	UART_SET_BAUDL(uart, uartl);
+	UART_SET_BAUDH(uart, uarth);
+
+	UART_RX_IRQ_ENABLE(uart);
+
+	/* Port speed changed, update the per-port timeout. */
+	uart_update_timeout(port, termios->c_cflag, baud);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static const char *arc_serial_type(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	return uart->port.type == PORT_ARC ? DRIVER_NAME : NULL;
+}
+
+/*
+ * Release the memory region(s) being used by 'port'.
+ */
+static void arc_serial_release_port(struct uart_port *port)
+{
+}
+
+/*
+ * Request the memory region(s) being used by '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)
+{
+	return 0;
+}
+
+/*
+ * Configure/autoconfigure the port.
+ */
+static void arc_serial_config_port(struct uart_port *port, int flags)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	if (flags & UART_CONFIG_TYPE &&
+	    arc_serial_request_port(&uart->port) == 0)
+		uart->port.type = PORT_ARC;
+}
+
+static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	while (!(UART_GET_STATUS(uart) & TXEMPTY))
+		cpu_relax();
+
+	UART_SET_DATA(uart, chr);
+}
+
+#ifdef CONFIG_CONSOLE_POLL
+static int arc_serial_poll_getchar(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+	unsigned char chr;
+
+	while (!(UART_GET_STATUS(uart) & RXEMPTY))
+		cpu_relax();
+
+	chr = UART_GET_DATA(uart);
+	return chr;
+}
+#endif
+
+static 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,
+	.enable_ms	= arc_serial_enable_ms,
+	.break_ctl	= arc_serial_break_ctl,
+	.startup	= arc_serial_startup,
+	.shutdown	= arc_serial_shutdown,
+	.set_termios	= arc_serial_set_termios,
+	.set_ldisc	= arc_serial_set_ldisc,
+	.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
+};
+
+static int __devinit
+arc_uart_init_one(struct platform_device *pdev, struct arc_uart_port *uart)
+{
+	struct resource *res, *res2;
+	unsigned long *plat_data;
+
+	if (pdev->id < 0 || pdev->id >= CONFIG_SERIAL_ARC_NR_PORTS) {
+		dev_err(&pdev->dev, "Wrong uart platform device id.\n");
+		return -ENOENT;
+	}
+
+	plat_data = ((unsigned long *)(pdev->dev.platform_data));
+	uart->baud = plat_data[0];
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!res2)
+		return -ENODEV;
+
+	uart->port.mapbase = res->start;
+	uart->port.membase = ioremap_nocache(res->start, resource_size(res));
+	if (!uart->port.membase)
+		/* No point of pr_err since UART itself is hosed here */
+		return -ENXIO;
+
+	uart->port.irq = res2->start;
+	uart->port.dev = &pdev->dev;
+	uart->port.iotype = UPIO_MEM;
+	uart->port.flags = UPF_BOOT_AUTOCONF;
+	uart->port.line = pdev->id;
+	uart->port.ops = &arc_serial_pops;
+
+	uart->port.uartclk = plat_data[1];
+	uart->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
+	 */
+	uart->port.ignore_status_mask = 0;
+
+
+	return 0;
+}
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+
+static int __devinit 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. ttyS1) 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)
+{
+	arc_serial_poll_putchar(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_serial_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 __init void early_serial_write(struct console *con, const char *s,
+					unsigned int n)
+{
+	struct uart_port *port = &arc_uart_ports[con->index].port;
+	unsigned int i;
+
+	for (i = 0; i < n; i++, s++) {
+		if (*s == '\n')
+			arc_serial_poll_putchar(port, '\r');
+		arc_serial_poll_putchar(port, *s);
+	}
+}
+
+static struct __initdata console arc_early_serial_console = {
+	.name = "early_ARCuart",
+	.write = early_serial_write,
+	.flags = CON_PRINTBUFFER | CON_BOOT,
+	.index = -1
+};
+
+static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
+{
+	arc_early_serial_console.index = pdev->id;
+
+	arc_uart_init_one(pdev, &arc_uart_ports[pdev->id]);
+
+	arc_serial_console_setup(&arc_early_serial_console, NULL);
+
+	register_console(&arc_early_serial_console);
+	return 0;
+}
+#endif
+
+
+static int __devinit arc_serial_probe(struct platform_device *pdev)
+{
+	struct arc_uart_port *uart;
+	int rc;
+
+	if (is_early_platform_device(pdev))
+		return arc_serial_probe_earlyprintk(pdev);
+
+	uart = &arc_uart_ports[pdev->id];
+	rc = arc_uart_init_one(pdev, uart);
+	if (rc)
+		return rc;
+
+	return uart_add_one_port(&arc_uart_driver, &uart->port);
+}
+
+static int __devexit arc_serial_remove(struct platform_device *pdev)
+{
+	/* This will never be called */
+	return 0;
+}
+
+static struct platform_driver arc_platform_driver = {
+	.probe = arc_serial_probe,
+	.remove = __devexit_p(arc_serial_remove),
+	.driver = {
+		.name = DRIVER_NAME,
+		.owner = THIS_MODULE,
+	 },
+};
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+/*
+ * Register an early platform driver of "earlyprintk" class.
+ * ARCH platform code installs the driver and probes the early devices
+ * The installation could rely on user specifying earlyprintk=xyx in cmd line
+ * or it could be done independently, for all "earlyprintk" class drivers.
+ * [see arch/arc/plat-arcfpga/platform.c]
+ */
+early_platform_init("earlyprintk", &arc_platform_driver);
+
+#endif  /* CONFIG_SERIAL_ARC_CONSOLE */
+
+static int __init arc_serial_init(void)
+{
+	int ret;
+
+	pr_info("Serial: ARC serial driver: platform register\n");
+
+	ret = uart_register_driver(&arc_uart_driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&arc_platform_driver);
+	if (ret) {
+		pr_debug("uart register failed\n");
+		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("plat-arcfpga/uart");
+MODULE_AUTHOR("Vineet Gupta");
+MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 0253c20..706a042 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -214,6 +214,9 @@
 /* Energy Micro efm32 SoC */
 #define PORT_EFMUART   100
 
+/* ARC (Synopsys) on-chip UART */
+#define PORT_ARC       101
+
 #ifdef __KERNEL__
 
 #include <linux/compiler.h>
-- 
1.7.4.1

Re: [PATCH] serial/arc-uart: Add new driver

[Alan Cox]

> +int __attribute__((weak)) running_on_iss;

Globals really ought to have sensible names, if they must exist at all.
Why is this needed ?

> +#define ARC_SERIAL_DEV_NAME	"ttyS"

ttyS is reserved by the 8250 driver. Use a different name

> /* ttySxx per Documentation/devices.txt */
> +#define ARC_SERIAL_MAJOR	4
> +#define ARC_SERIAL_MINOR	64

Use dynamic assignments

> +static void arc_serial_rx_chars(struct arc_uart_port *uart)
> +{
> +	struct tty_struct *tty = NULL;
> +	unsigned int status, ch, flg = 0;
> +
> +	tty = uart->port.state->port.tty;

Please get rid of the unneeded initialisers for things like tty - they
just hide bugs later.

For locking purposes you need to be doing

	tty = tty_port_tty_get(&uart->port.state->port);

	if (tty) {

		stuff

		tty_kref_put(tty);


so that the tty cannot vanish under you on a hangup. As you reference
it in several spots it might make sense to do that once if either
RXIENB/TXIENB is set and then pass it to the tx/rx handlers ?


> +static void arc_serial_break_ctl(struct uart_port *port, int
> break_state) +{
> +	/* ARC UART doesn't support sendind Break signal */

sending ..

> +static void arc_serial_set_ldisc(struct uart_port *port, int ld)
> +{
> +	/* this might need implementing for the touch driver */
> +}

Is this a left over comment or somehting else ?

> +static void
> +arc_serial_set_termios(struct uart_port *port, struct ktermios
> *termios,
> +		       struct ktermios *old)
> +{
> +	struct arc_uart_port *uart = (struct arc_uart_port *)port;
> +	unsigned int baud, uartl, uarth, hw_val;
> +	unsigned long flags;
> +

Two things here. Firstly you want to write the actual baud back to the
termios (tty_termios_encode_baud_rate) unless B0 is set.

Secondly if you don't support hardware flow control, character size
setting etc then you need to set those bits back so the caller knows.
Two ways to do that. Either initialise the default termios for the tty
type to the correct values and use tty_termios_copy_hw() or set them in
the termios handler.

Alan

Re: [PATCH] serial/arc-uart: Add new driver

[Vineet Gupta]

On Friday 28 September 2012 06:32 PM, Alan Cox wrote:

>> +static void
>> +arc_serial_set_termios(struct uart_port *port, struct ktermios
>> *termios,
>> +		       struct ktermios *old)
>> +{
>> +	struct arc_uart_port *uart = (struct arc_uart_port *)port;
>> +	unsigned int baud, uartl, uarth, hw_val;
>> +	unsigned long flags;
>> +
> Two things here. Firstly you want to write the actual baud back to the
> termios (tty_termios_encode_baud_rate) unless B0 is set.
>
> Secondly if you don't support hardware flow control, character size
> setting etc then you need to set those bits back so the caller knows.
> Two ways to do that. Either initialise the default termios for the tty
> type to the correct values and use tty_termios_copy_hw() or set them in
> the termios handler.

Just to give you an idea, is something on the lines of following OK for
both the above points above !

-       uart_update_timeout(port, termios->c_cflag, baud);
+       new->c_cflag &= ~(CMSPAR|CRTSCTS);  /* Don't care for
parity/flow ctrl */
+
+       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);
 

Respun patch to follow shortly.

Thx,
Vineet

[PATCH v4] serial/arc-uart: Add New Driver

[Vineet.Gupta1]

From: Vineet Gupta <vgupta@synopsys.com>

Hi Greg,

Rebased off of tty-next and verfied that it builds fine.
Please consider applying.

Thanks,
Vineet

v4:
* UAPI disintegration fallout for serial_core.h
* rebased off of tty-next

v3:
* Removed empty arc_serial_set_ldisc()
* More set_termios fixes - CSIZE forced to CS8 (for 8N1)
* global @running_on_iss replaced with platform data, saved in device
  specific port structure.

v2:
* ttyARC used as device name
* Dynamic assignment of major/minor numbers.
* Ref counting tty in rx routine to prevent it from disappearing in
  case of a hangup
* set_termios fixes:
  - hardware flow control/parity are marked as unsupported
  - baud written back to termios
* cosmetics such as commenting the need for @running_on_iss, empty lines
  etc

Vineet Gupta (1):
  serial/arc-uart: Add new driver

 drivers/tty/serial/Kconfig       |   25 ++
 drivers/tty/serial/Makefile      |    1 +
 drivers/tty/serial/arc_uart.c    |  747 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/serial_core.h |    2 +
 4 files changed, 775 insertions(+), 0 deletions(-)
 create mode 100644 drivers/tty/serial/arc_uart.c

-- 
1.7.4.1

[PATCH] serial/arc-uart: Add new driver

[Vineet.Gupta1]

From: Vineet Gupta <vgupta@synopsys.com>

Driver for non-standard on-chip UART, instantiated in the ARC (Synopsys)
FPGA Boards such as ARCAngel4/ML50x

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 drivers/tty/serial/Kconfig       |   25 ++
 drivers/tty/serial/Makefile      |    1 +
 drivers/tty/serial/arc_uart.c    |  747 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/serial_core.h |    2 +
 4 files changed, 775 insertions(+), 0 deletions(-)
 create mode 100644 drivers/tty/serial/arc_uart.c

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 2a53be5..efee7fe 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1423,4 +1423,29 @@ config SERIAL_EFM32_UART_CONSOLE
 	depends on SERIAL_EFM32_UART=y
 	select SERIAL_CORE_CONSOLE
 
+config SERIAL_ARC
+	bool "ARC UART driver support"
+	select SERIAL_CORE
+	default y
+	help
+	  Driver for on-chip UART for ARC(Synopsys) for the legacy
+	  FPGA Boards (ML50x/ARCAngel4)
+
+config SERIAL_ARC_CONSOLE
+	bool
+	select SERIAL_CORE_CONSOLE
+	depends on SERIAL_ARC=y
+	default y
+	help
+	  Enable system Console on ARC UART
+
+config SERIAL_ARC_NR_PORTS
+	int 'Number of ports'
+	range 1 3
+	default 1
+	depends on SERIAL_ARC
+	help
+	  Set this to the number of serial ports you want the driver
+	  to support.
+
 endmenu
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 4f694da..df1b998 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -82,3 +82,4 @@ obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
 obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
 obj-$(CONFIG_SERIAL_AR933X)   += ar933x_uart.o
 obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
+obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
new file mode 100644
index 0000000..9215bf4
--- /dev/null
+++ b/drivers/tty/serial/arc_uart.c
@@ -0,0 +1,747 @@
+/*
+ * ARC On-Chip(fpga) UART Driver
+ *
+ * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.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.
+ *
+ * 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>
+
+/*************************************
+ * 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	1
+#define R_ID2	2
+#define R_ID3	3
+#define R_DATA	4
+#define R_STS	5
+#define R_BAUDL	6
+#define R_BAUDH	7
+
+/* 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(uart, reg)      ((unsigned int *)uart->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;
+	int is_emulated;	/* H/w vs. Instruction Set Simulator */
+};
+
+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,
+#else
+	.cons		= NULL,
+#endif
+};
+
+static void arc_serial_stop_rx(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	UART_RX_IRQ_DISABLE(uart);
+}
+
+static void arc_serial_stop_tx(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	while (!(UART_GET_STATUS(uart) & TXEMPTY))
+		cpu_relax();
+
+	UART_TX_IRQ_DISABLE(uart);
+}
+
+/*
+ * Return TIOCSER_TEMT when transmitter is not busy.
+ */
+static unsigned int arc_serial_tx_empty(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+	unsigned int stat;
+
+	stat = UART_GET_STATUS(uart);
+	if (stat & TXEMPTY)
+		return TIOCSER_TEMT;
+	else
+		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 / tty->hw_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 arc_uart_port *uart)
+{
+	struct circ_buf *xmit = &uart->port.state->xmit;
+	int sent = 0;
+	unsigned char ch;
+
+	if (unlikely(uart->port.x_char)) {
+		UART_SET_DATA(uart, uart->port.x_char);
+		uart->port.icount.tx++;
+		uart->port.x_char = 0;
+		sent = 1;
+	} else if (xmit->tail != xmit->head) {	/* TODO: uart_circ_empty */
+		ch = xmit->buf[xmit->tail];
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		uart->port.icount.tx++;
+		while (!(UART_GET_STATUS(uart) & TXEMPTY))
+			cpu_relax();
+		UART_SET_DATA(uart, 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(&uart->port);
+
+	if (sent)
+		UART_TX_IRQ_ENABLE(uart);
+}
+
+/*
+ * 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)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	arc_serial_tx_chars(uart);
+}
+
+static void arc_serial_rx_chars(struct arc_uart_port *uart)
+{
+	struct tty_struct *tty = tty_port_tty_get(&uart->port.state->port);
+	unsigned int status, ch, flg = 0;
+
+	if (!tty)
+		return;
+
+	/*
+	 * 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.
+	 */
+	while (!((status = UART_GET_STATUS(uart)) & RXEMPTY)) {
+
+		ch = UART_GET_DATA(uart);
+		uart->port.icount.rx++;
+
+		if (unlikely(status & (RXOERR | RXFERR))) {
+			if (status & RXOERR) {
+				uart->port.icount.overrun++;
+				flg = TTY_OVERRUN;
+				UART_CLR_STATUS(uart, RXOERR);
+			}
+
+			if (status & RXFERR) {
+				uart->port.icount.frame++;
+				flg = TTY_FRAME;
+				UART_CLR_STATUS(uart, RXFERR);
+			}
+		} else
+			flg = TTY_NORMAL;
+
+		if (unlikely(uart_handle_sysrq_char(&uart->port, ch)))
+			goto done;
+
+		uart_insert_char(&uart->port, status, RXOERR, ch, flg);
+
+done:
+		tty_flip_buffer_push(tty);
+	}
+
+	tty_kref_put(tty);
+}
+
+/*
+ * 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 arc_uart_port *uart = dev_id;
+	unsigned int status;
+
+	status = UART_GET_STATUS(uart);
+
+	/*
+	 * 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) && !(status & RXEMPTY)) {
+
+		/* already in ISR, no need of xx_irqsave */
+		spin_lock(&uart->port.lock);
+		arc_serial_rx_chars(uart);
+		spin_unlock(&uart->port.lock);
+	}
+
+	if ((status & TXIENB) && (status & TXEMPTY)) {
+
+		/* Unconditionally disable further Tx-Interrupts.
+		 * will be enabled by tx_chars() if needed.
+		 */
+		UART_TX_IRQ_DISABLE(uart);
+
+		spin_lock(&uart->port.lock);
+
+		if (!uart_tx_stopped(&uart->port))
+			arc_serial_tx_chars(uart);
+
+		spin_unlock(&uart->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 */
+}
+
+/* Enable Modem Status Interrupts */
+
+static void arc_serial_enable_ms(struct uart_port *port)
+{
+	/* MSR 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)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	/* Before we hook up the ISR, Disable all UART Interrupts */
+	UART_ALL_IRQ_DISABLE(uart);
+
+	if (request_irq(uart->port.irq, arc_serial_isr, 0, "arc uart rx-tx",
+			uart)) {
+		pr_warn("Unable to attach ARC UART interrupt\n");
+		return -EBUSY;
+	}
+
+	UART_RX_IRQ_ENABLE(uart); /* Only Rx IRQ enabled to begin with */
+
+	return 0;
+}
+
+/* This is not really needed */
+static void arc_serial_shutdown(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+	free_irq(uart->port.irq, uart);
+}
+
+static void
+arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
+		       struct ktermios *old)
+{
+	struct arc_uart_port *uart = (struct arc_uart_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;
+
+	/*
+	 * UART ISS(Instruction Set simulator) emulation has a subtle bug:
+	 * A existing value of Baudh = 0 is used as a indication to startup
+	 * it's internal state machine.
+	 * Thus if baudh is set to 0, 2 times, it chokes.
+	 * This happens with BAUD=115200 and the formaula above
+	 * Until that is fixed, when running on ISS, we will set baudh to !0
+	 */
+	if (uart->is_emulated)
+		uarth = 1;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	UART_ALL_IRQ_DISABLE(uart);
+
+	UART_SET_BAUDL(uart, uartl);
+	UART_SET_BAUDH(uart, uarth);
+
+	UART_RX_IRQ_ENABLE(uart);
+
+	/*
+	 * 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)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	return uart->port.type == PORT_ARC ? DRIVER_NAME : NULL;
+}
+
+/*
+ * Release the memory region(s) being used by 'port'.
+ */
+static void arc_serial_release_port(struct uart_port *port)
+{
+}
+
+/*
+ * Request the memory region(s) being used by '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)
+{
+	return 0;
+}
+
+/*
+ * Configure/autoconfigure the port.
+ */
+static void arc_serial_config_port(struct uart_port *port, int flags)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	if (flags & UART_CONFIG_TYPE &&
+	    arc_serial_request_port(&uart->port) == 0)
+		uart->port.type = PORT_ARC;
+}
+
+static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+
+	while (!(UART_GET_STATUS(uart) & TXEMPTY))
+		cpu_relax();
+
+	UART_SET_DATA(uart, chr);
+}
+
+#ifdef CONFIG_CONSOLE_POLL
+static int arc_serial_poll_getchar(struct uart_port *port)
+{
+	struct arc_uart_port *uart = (struct arc_uart_port *)port;
+	unsigned char chr;
+
+	while (!(UART_GET_STATUS(uart) & RXEMPTY))
+		cpu_relax();
+
+	chr = UART_GET_DATA(uart);
+	return chr;
+}
+#endif
+
+static 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,
+	.enable_ms	= arc_serial_enable_ms,
+	.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
+};
+
+static int __devinit
+arc_uart_init_one(struct platform_device *pdev, struct arc_uart_port *uart)
+{
+	struct resource *res, *res2;
+	unsigned long *plat_data;
+
+	if (pdev->id < 0 || pdev->id >= CONFIG_SERIAL_ARC_NR_PORTS) {
+		dev_err(&pdev->dev, "Wrong uart platform device id.\n");
+		return -ENOENT;
+	}
+
+	plat_data = ((unsigned long *)(pdev->dev.platform_data));
+	uart->baud = plat_data[0];
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!res2)
+		return -ENODEV;
+
+	uart->port.mapbase = res->start;
+	uart->port.membase = ioremap_nocache(res->start, resource_size(res));
+	if (!uart->port.membase)
+		/* No point of pr_err since UART itself is hosed here */
+		return -ENXIO;
+
+	uart->port.irq = res2->start;
+	uart->port.dev = &pdev->dev;
+	uart->port.iotype = UPIO_MEM;
+	uart->port.flags = UPF_BOOT_AUTOCONF;
+	uart->port.line = pdev->id;
+	uart->port.ops = &arc_serial_pops;
+
+	uart->port.uartclk = plat_data[1];
+	uart->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
+	 */
+	uart->port.ignore_status_mask = 0;
+
+	/* Real Hardware vs. emulated to work around a bug */
+	uart->is_emulated = !!plat_data[2];
+
+	return 0;
+}
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+
+static int __devinit 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)
+{
+	arc_serial_poll_putchar(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 __init void early_serial_write(struct console *con, const char *s,
+					unsigned int n)
+{
+	struct uart_port *port = &arc_uart_ports[con->index].port;
+	unsigned int i;
+
+	for (i = 0; i < n; i++, s++) {
+		if (*s == '\n')
+			arc_serial_poll_putchar(port, '\r');
+		arc_serial_poll_putchar(port, *s);
+	}
+}
+
+static struct __initdata console arc_early_serial_console = {
+	.name = "early_ARCuart",
+	.write = early_serial_write,
+	.flags = CON_PRINTBUFFER | CON_BOOT,
+	.index = -1
+};
+
+static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
+{
+	arc_early_serial_console.index = pdev->id;
+
+	arc_uart_init_one(pdev, &arc_uart_ports[pdev->id]);
+
+	arc_serial_console_setup(&arc_early_serial_console, NULL);
+
+	register_console(&arc_early_serial_console);
+	return 0;
+}
+#endif
+
+
+static int __devinit arc_serial_probe(struct platform_device *pdev)
+{
+	struct arc_uart_port *uart;
+	int rc;
+
+	if (is_early_platform_device(pdev))
+		return arc_serial_probe_earlyprintk(pdev);
+
+	uart = &arc_uart_ports[pdev->id];
+	rc = arc_uart_init_one(pdev, uart);
+	if (rc)
+		return rc;
+
+	return uart_add_one_port(&arc_uart_driver, &uart->port);
+}
+
+static int __devexit arc_serial_remove(struct platform_device *pdev)
+{
+	/* This will never be called */
+	return 0;
+}
+
+static struct platform_driver arc_platform_driver = {
+	.probe = arc_serial_probe,
+	.remove = __devexit_p(arc_serial_remove),
+	.driver = {
+		.name = DRIVER_NAME,
+		.owner = THIS_MODULE,
+	 },
+};
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+/*
+ * Register an early platform driver of "earlyprintk" class.
+ * ARCH platform code installs the driver and probes the early devices
+ * The installation could rely on user specifying earlyprintk=xyx in cmd line
+ * or it could be done independently, for all "earlyprintk" class drivers.
+ * [see arch/arc/plat-arcfpga/platform.c]
+ */
+early_platform_init("earlyprintk", &arc_platform_driver);
+
+#endif  /* CONFIG_SERIAL_ARC_CONSOLE */
+
+static int __init arc_serial_init(void)
+{
+	int ret;
+
+	pr_info("Serial: ARC serial driver: platform register\n");
+
+	ret = uart_register_driver(&arc_uart_driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&arc_platform_driver);
+	if (ret) {
+		pr_debug("uart register failed\n");
+		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("plat-arcfpga/uart");
+MODULE_AUTHOR("Vineet Gupta");
+MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");
diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
index 7e1ab20..ebcc73f 100644
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -215,5 +215,7 @@
 /* Energy Micro efm32 SoC */
 #define PORT_EFMUART   100
 
+/* ARC (Synopsys) on-chip UART */
+#define PORT_ARC       101
 
 #endif /* _UAPILINUX_SERIAL_CORE_H */
-- 
1.7.4.1

Re: [PATCH] serial/arc-uart: Add new driver

[Greg KH]

On Thu, Oct 25, 2012 at 12:00:08PM +0530, Vineet.Gupta1@synopsys.com wrote:
> From: Vineet Gupta <vgupta@synopsys.com>
> 
> Driver for non-standard on-chip UART, instantiated in the ARC (Synopsys)
> FPGA Boards such as ARCAngel4/ML50x
> 
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> ---
>  drivers/tty/serial/Kconfig       |   25 ++
>  drivers/tty/serial/Makefile      |    1 +
>  drivers/tty/serial/arc_uart.c    |  747 ++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/serial_core.h |    2 +
>  4 files changed, 775 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/tty/serial/arc_uart.c
> 
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 2a53be5..efee7fe 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1423,4 +1423,29 @@ config SERIAL_EFM32_UART_CONSOLE
>  	depends on SERIAL_EFM32_UART=y
>  	select SERIAL_CORE_CONSOLE
>  
> +config SERIAL_ARC
> +	bool "ARC UART driver support"
> +	select SERIAL_CORE
> +	default y
> +	help
> +	  Driver for on-chip UART for ARC(Synopsys) for the legacy
> +	  FPGA Boards (ML50x/ARCAngel4)

Unless you will break a user's box, NEVER define a default value for a
new configuration option as y.

And why can't I select this driver as a module?

> +
> +config SERIAL_ARC_CONSOLE
> +	bool
> +	select SERIAL_CORE_CONSOLE
> +	depends on SERIAL_ARC=y
> +	default y
> +	help
> +	  Enable system Console on ARC UART
> +
> +config SERIAL_ARC_NR_PORTS
> +	int 'Number of ports'
> +	range 1 3
> +	default 1
> +	depends on SERIAL_ARC
> +	help
> +	  Set this to the number of serial ports you want the driver
> +	  to support.
> +
>  endmenu
> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
> index 4f694da..df1b998 100644
> --- a/drivers/tty/serial/Makefile
> +++ b/drivers/tty/serial/Makefile
> @@ -82,3 +82,4 @@ obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
>  obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
>  obj-$(CONFIG_SERIAL_AR933X)   += ar933x_uart.o
>  obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
> +obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
> diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
> new file mode 100644
> index 0000000..9215bf4
> --- /dev/null
> +++ b/drivers/tty/serial/arc_uart.c
> @@ -0,0 +1,747 @@
> +/*
> + * ARC On-Chip(fpga) UART Driver
> + *
> + * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.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.
> + *
> + * 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

Are you sure this works?  Don't you usually need to include some .h
files before you check these config values?

> +
> +#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>
> +
> +/*************************************
> + * 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	1
> +#define R_ID2	2
> +#define R_ID3	3
> +#define R_DATA	4
> +#define R_STS	5
> +#define R_BAUDL	6
> +#define R_BAUDH	7
> +
> +/* 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(uart, reg)      ((unsigned int *)uart->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))

What happens when you run sparse on this driver?

thanks,

greg k-h

Re: [PATCH] serial/arc-uart: Add new driver

[Vineet Gupta]

On Friday 26 October 2012 12:06 AM, Greg KH wrote:
> On Thu, Oct 25, 2012 at 12:00:08PM +0530, Vineet.Gupta1@synopsys.com wrote:
>> From: Vineet Gupta <vgupta@synopsys.com>
>>
>> Driver for non-standard on-chip UART, instantiated in the ARC (Synopsys)
>> FPGA Boards such as ARCAngel4/ML50x
>>
>> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
>> ---
>>  drivers/tty/serial/Kconfig       |   25 ++
>>  drivers/tty/serial/Makefile      |    1 +
>>  drivers/tty/serial/arc_uart.c    |  747 ++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/serial_core.h |    2 +
>>  4 files changed, 775 insertions(+), 0 deletions(-)
>>  create mode 100644 drivers/tty/serial/arc_uart.c
>>
>> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
>> index 2a53be5..efee7fe 100644
>> --- a/drivers/tty/serial/Kconfig
>> +++ b/drivers/tty/serial/Kconfig
>> @@ -1423,4 +1423,29 @@ config SERIAL_EFM32_UART_CONSOLE
>>  	depends on SERIAL_EFM32_UART=y
>>  	select SERIAL_CORE_CONSOLE
>>  
>> +config SERIAL_ARC
>> +	bool "ARC UART driver support"
>> +	select SERIAL_CORE
>> +	default y
>> +	help
>> +	  Driver for on-chip UART for ARC(Synopsys) for the legacy
>> +	  FPGA Boards (ML50x/ARCAngel4)
> Unless you will break a user's box, NEVER define a default value for a
> new configuration option as y.

OK !

> And why can't I select this driver as a module?

Because it's missing the equivalent of following (plus some more changes)
-       bool "ARC UART driver support"
+      tristate "ARC UART driver support"

ARC platform (where this driver originates from) always had system
console on UART - thus we never had the need for making it a loadable
module. But I guess as a matter of principle it nevertheless needs to
work - fixed in the next revision !

>> +
>> +config SERIAL_ARC_CONSOLE
>> +	bool
>> +	select SERIAL_CORE_CONSOLE
>> +	depends on SERIAL_ARC=y
>> +	default y
>> +	help
>> +	  Enable system Console on ARC UART
>> +
>> +config SERIAL_ARC_NR_PORTS
>> +	int 'Number of ports'
>> +	range 1 3
>> +	default 1
>> +	depends on SERIAL_ARC
>> +	help
>> +	  Set this to the number of serial ports you want the driver
>> +	  to support.
>> +
>>  endmenu
>> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
>> index 4f694da..df1b998 100644
>> --- a/drivers/tty/serial/Makefile
>> +++ b/drivers/tty/serial/Makefile
>> @@ -82,3 +82,4 @@ obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
>>  obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
>>  obj-$(CONFIG_SERIAL_AR933X)   += ar933x_uart.o
>>  obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
>> +obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
>> diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
>> new file mode 100644
>> index 0000000..9215bf4
>> --- /dev/null
>> +++ b/drivers/tty/serial/arc_uart.c
>> @@ -0,0 +1,747 @@
>> +/*
>> + * ARC On-Chip(fpga) UART Driver
>> + *
>> + * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.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.
>> + *
>> + * 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
> Are you sure this works?  Don't you usually need to include some .h
> files before you check these config values?

We've been using the exact same driver for years - literally.

AFAIK, all the CONFIG_xxx items come in from generated autoconf.h which
is included implicitly by build system via cmd line based -include
kconfig.h, thus any explicit header is not needed for them. Also
SUPPORT_SYSRQ needs to be defined BEFORE including any header because
that is the way serial_core.h build can be influenced in a non-ambiguous
way.

>> +
>> +#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>
>> +
>> +/*************************************
>> + * 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	1
>> +#define R_ID2	2
>> +#define R_ID3	3
>> +#define R_DATA	4
>> +#define R_STS	5
>> +#define R_BAUDL	6
>> +#define R_BAUDH	7
>> +
>> +/* 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(uart, reg)      ((unsigned int *)uart->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))
> What happens when you run sparse on this driver?

(1) The cast was indeed causing warning - that's now fixed, with an
equivalent of following:

-#define R_ID1  1
-#define R_ID2  2
-#define R_ID3  3
-#define R_DATA 4
-#define R_STS  5
-#define R_BAUDL        6
-#define R_BAUDH        7
+#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

-#define RBASE(uart, reg)      ((unsigned int *)uart->port.membase + reg)
+#define RBASE(uart, reg)     (uart->port.membase + reg)

(2) Other two seem to be false warnings for imbalance of
spin_lock_irqsave/restore, which otherwise seem OK to me!


>
> thanks,
>
> greg k-h