[PATCH v5] serial/arc-uart: Add new driver

[PATCH v5] serial/arc-uart: Add new driver

[Vineet.Gupta1]

From: Vineet Gupta <vgupta@synopsys.com>

Hi Greg,

Here's the updated revision with fixes per your review comments.
-Rebased off tty-next tip.
-Build tested for x86, both as builtin and as module
-Same driver (as module) verified on ARCAngel4 Board.

Please consider applying.

Thanks,
Vineet

v5:
* Driver now builds as module; default !y
* Fixed some build wreckage due to SERIAL_ARC && !SERIAL_ARC_CONSOLE
* Fixed a sparse warning due to forced cast, hence reg offsets now in bytes

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       |   23 ++
 drivers/tty/serial/Makefile      |    1 +
 drivers/tty/serial/arc_uart.c    |  754 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/serial_core.h |    2 +
 4 files changed, 780 insertions(+), 0 deletions(-)
 create mode 100644 drivers/tty/serial/arc_uart.c

-- 
1.7.4.1

[PATCH v5] 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       |   23 ++
 drivers/tty/serial/Makefile      |    1 +
 drivers/tty/serial/arc_uart.c    |  754 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/serial_core.h |    2 +
 4 files changed, 780 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..b176801 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1423,4 +1423,27 @@ config SERIAL_EFM32_UART_CONSOLE
 	depends on SERIAL_EFM32_UART=y
 	select SERIAL_CORE_CONSOLE
 
+config SERIAL_ARC
+	tristate "ARC UART driver support"
+	select SERIAL_CORE
+	help
+	  Driver for on-chip UART for ARC(Synopsys) for the legacy
+	  FPGA Boards (ML50x/ARCAngel4)
+
+config SERIAL_ARC_CONSOLE
+	bool "Console on ARC UART"
+	depends on SERIAL_ARC=y
+	select SERIAL_CORE_CONSOLE
+	help
+	  Enable system Console on ARC UART
+
+config SERIAL_ARC_NR_PORTS
+	int "Number of ARC UART ports"
+	depends on SERIAL_ARC
+	range 1 3
+	default "1"
+	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..c12efae
--- /dev/null
+++ b/drivers/tty/serial/arc_uart.c
@@ -0,0 +1,754 @@
+/*
+ * 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	4
+#define R_ID2	8
+#define R_ID3	12
+#define R_DATA	16
+#define R_STS	20
+#define R_BAUDL	24
+#define R_BAUDH	28
+
+/* Bits for UART Status Reg (R/W) */
+#define RXIENB  0x04	/* Receive Interrupt Enable */
+#define TXIENB  0x40	/* Transmit Interrupt Enable */
+
+#define RXEMPTY 0x20	/* Receive FIFO Empty: No char receivede */
+#define TXEMPTY 0x80	/* Transmit FIFO Empty, thus char can be written into */
+
+#define RXFULL  0x08	/* Receive FIFO full */
+#define RXFULL1 0x10	/* Receive FIFO has space for 1 char (tot space=4) */
+
+#define RXFERR  0x01	/* Frame Error: Stop Bit not detected */
+#define RXOERR  0x02	/* OverFlow Err: Char recv but RXFULL still set */
+
+/* Uart bit fiddling helpers: lowest level */
+#define RBASE(uart, reg)      (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;
+}
+
+#if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_ARC_CONSOLE)
+
+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);
+}
+#endif
+
+#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;
+}
+#else
+static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
+{
+	return -ENODEV;
+}
+#endif	/* CONFIG_SERIAL_ARC_CONSOLE */
+
+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 v5] serial/arc-uart: Add new driver

[Felipe Balbi]

[-- Attachment #1: Type: text/plain, Size: 25302 bytes --]

On Fri, Oct 26, 2012 at 05:33:16PM +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       |   23 ++
>  drivers/tty/serial/Makefile      |    1 +
>  drivers/tty/serial/arc_uart.c    |  754 ++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/serial_core.h |    2 +
>  4 files changed, 780 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..b176801 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1423,4 +1423,27 @@ config SERIAL_EFM32_UART_CONSOLE
>  	depends on SERIAL_EFM32_UART=y
>  	select SERIAL_CORE_CONSOLE
>  
> +config SERIAL_ARC
> +	tristate "ARC UART driver support"
> +	select SERIAL_CORE
> +	help
> +	  Driver for on-chip UART for ARC(Synopsys) for the legacy
> +	  FPGA Boards (ML50x/ARCAngel4)
> +
> +config SERIAL_ARC_CONSOLE
> +	bool "Console on ARC UART"
> +	depends on SERIAL_ARC=y
> +	select SERIAL_CORE_CONSOLE
> +	help
> +	  Enable system Console on ARC UART
> +
> +config SERIAL_ARC_NR_PORTS
> +	int "Number of ARC UART ports"
> +	depends on SERIAL_ARC
> +	range 1 3
> +	default "1"
> +	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..c12efae
> --- /dev/null
> +++ b/drivers/tty/serial/arc_uart.c
> @@ -0,0 +1,754 @@
> +/*
> + * 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	4
> +#define R_ID2	8
> +#define R_ID3	12
> +#define R_DATA	16
> +#define R_STS	20
> +#define R_BAUDL	24
> +#define R_BAUDH	28
> +
> +/* Bits for UART Status Reg (R/W) */
> +#define RXIENB  0x04	/* Receive Interrupt Enable */
> +#define TXIENB  0x40	/* Transmit Interrupt Enable */
> +
> +#define RXEMPTY 0x20	/* Receive FIFO Empty: No char receivede */
> +#define TXEMPTY 0x80	/* Transmit FIFO Empty, thus char can be written into */
> +
> +#define RXFULL  0x08	/* Receive FIFO full */
> +#define RXFULL1 0x10	/* Receive FIFO has space for 1 char (tot space=4) */
> +
> +#define RXFERR  0x01	/* Frame Error: Stop Bit not detected */
> +#define RXOERR  0x02	/* OverFlow Err: Char recv but RXFULL still set */
> +
> +/* Uart bit fiddling helpers: lowest level */
> +#define RBASE(uart, reg)      (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,

else branch isn't necessary. The structure is declared static and
everything is initialized to zero unless overwritten by code.

> +#endif
> +};
> +
> +static void arc_serial_stop_rx(struct uart_port *port)
> +{
> +	struct arc_uart_port *uart = (struct arc_uart_port *)port;

I would suggest using container_of() here. It's very unlikely to happen,
but if another field is added before struct uart_port member in your
structure, this will break.

> +	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;

else is unnecessary you can convert this into:

	if (stat & TXEMPTY)
		return TIOCSER_TEMT;

	return 0;

> +}
> +
> +/*
> + * Driver internal routine, used by both tty(serial core) as well as tx-isr
> + *  -Called under spinlock in either cases
> + *  -also tty->stopped / 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;

can this really happen ? why would you receive characters while tty is
NULL ?

> +	/*
> +	 * 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;
> +}

why all these empty functions with wrong comments above them ??

> +/*
> + * 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;
> +}
> +
> +#if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_ARC_CONSOLE)
> +
> +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);
> +}
> +#endif
> +
> +#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;
> +}
> +#else
> +static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
> +{
> +	return -ENODEV;
> +}
> +#endif	/* CONFIG_SERIAL_ARC_CONSOLE */
> +
> +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");

please remove this line, it's just useless IMHO.

-- 
balbi

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [PATCH v5] serial/arc-uart: Add new driver

[Vineet Gupta]

On Friday 26 October 2012 05:40 PM, Felipe Balbi wrote:
> On Fri, Oct 26, 2012 at 05:33:16PM +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       |   23 ++
>>  drivers/tty/serial/Makefile      |    1 +
>>  drivers/tty/serial/arc_uart.c    |  754 ++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/serial_core.h |    2 +
>>  4 files changed, 780 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..b176801 100644
>> --- a/drivers/tty/serial/Kconfig
>> +++ b/drivers/tty/serial/Kconfig
>> @@ -1423,4 +1423,27 @@ config SERIAL_EFM32_UART_CONSOLE
>>  	depends on SERIAL_EFM32_UART=y
>>  	select SERIAL_CORE_CONSOLE
>>  
>> +config SERIAL_ARC
>> +	tristate "ARC UART driver support"
>> +	select SERIAL_CORE
>> +	help
>> +	  Driver for on-chip UART for ARC(Synopsys) for the legacy
>> +	  FPGA Boards (ML50x/ARCAngel4)
>> +
>> +config SERIAL_ARC_CONSOLE
>> +	bool "Console on ARC UART"
>> +	depends on SERIAL_ARC=y
>> +	select SERIAL_CORE_CONSOLE
>> +	help
>> +	  Enable system Console on ARC UART
>> +
>> +config SERIAL_ARC_NR_PORTS
>> +	int "Number of ARC UART ports"
>> +	depends on SERIAL_ARC
>> +	range 1 3
>> +	default "1"
>> +	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..c12efae
>> --- /dev/null
>> +++ b/drivers/tty/serial/arc_uart.c
>> @@ -0,0 +1,754 @@
>> +/*
>> + * 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	4
>> +#define R_ID2	8
>> +#define R_ID3	12
>> +#define R_DATA	16
>> +#define R_STS	20
>> +#define R_BAUDL	24
>> +#define R_BAUDH	28
>> +
>> +/* Bits for UART Status Reg (R/W) */
>> +#define RXIENB  0x04	/* Receive Interrupt Enable */
>> +#define TXIENB  0x40	/* Transmit Interrupt Enable */
>> +
>> +#define RXEMPTY 0x20	/* Receive FIFO Empty: No char receivede */
>> +#define TXEMPTY 0x80	/* Transmit FIFO Empty, thus char can be written into */
>> +
>> +#define RXFULL  0x08	/* Receive FIFO full */
>> +#define RXFULL1 0x10	/* Receive FIFO has space for 1 char (tot space=4) */
>> +
>> +#define RXFERR  0x01	/* Frame Error: Stop Bit not detected */
>> +#define RXOERR  0x02	/* OverFlow Err: Char recv but RXFULL still set */
>> +
>> +/* Uart bit fiddling helpers: lowest level */
>> +#define RBASE(uart, reg)      (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,
> else branch isn't necessary. The structure is declared static and
> everything is initialized to zero unless overwritten by code.

Correct - Fixed in next ver !

>> +#endif
>> +};
>> +
>> +static void arc_serial_stop_rx(struct uart_port *port)
>> +{
>> +	struct arc_uart_port *uart = (struct arc_uart_port *)port;
> I would suggest using container_of() here. It's very unlikely to happen,
> but if another field is added before struct uart_port member in your
> structure, this will break.

I agree  that container_of() would make it future safe - but I don't
foresee any significant changes to driver specially the arc_uart_port
structure.

>> +	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;
> else is unnecessary you can convert this into:
>
> 	if (stat & TXEMPTY)
> 		return TIOCSER_TEMT;
>
> 	return 0;

OK !

>
>> +}
>> +
>> +/*
>> + * 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;
> can this really happen ? why would you receive characters while tty is
> NULL ?

Since we are getting a ref to tty - it makes sense to check if the
pointer is not NULL. Alan had pointed to a possible hangup race which
could yield a NULL tty. But I'm not really an expert in serial core to
be sure if at all this will happen - so added the check.

>> +	/*
>> +	 * 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;
>> +}
> why all these empty functions with wrong comments above them ??

Copy/paste cruft. Empty functions deleted in next ver !
Regarding verify_port, I'm not sure whether it needs to elaborately
check for PORT_UNKNOWN -> PORT_ARC or can we simply continue to return
0. But IMHO the comment in there is right. No ?
 
>> +/*
>> + * 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;
>> +}
>> +
>> +#if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_ARC_CONSOLE)
>> +
>> +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);
>> +}
>> +#endif
>> +
>> +#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;
>> +}
>> +#else
>> +static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
>> +{
>> +	return -ENODEV;
>> +}
>> +#endif	/* CONFIG_SERIAL_ARC_CONSOLE */
>> +
>> +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");
> please remove this line, it's just useless IMHO.

It has helped me enough in past when debugging the uncoupling of driver
from ARC platform code. I'd rather keep it !

Many thanks for your review ! Once I see your reply I'll respin the next
version.

-Vineet

Re: [PATCH v5] serial/arc-uart: Add new driver

[Felipe Balbi]

[-- Attachment #1: Type: text/plain, Size: 18902 bytes --]

hi,

On Fri, Oct 26, 2012 at 06:17:26PM +0530, Vineet Gupta wrote:
> >> +#endif
> >> +};
> >> +
> >> +static void arc_serial_stop_rx(struct uart_port *port)
> >> +{
> >> +	struct arc_uart_port *uart = (struct arc_uart_port *)port;
> > I would suggest using container_of() here. It's very unlikely to happen,
> > but if another field is added before struct uart_port member in your
> > structure, this will break.
> 
> I agree  that container_of() would make it future safe - but I don't
> foresee any significant changes to driver specially the arc_uart_port
> structure.

I would still do it. The way code is right now, container_of() will be
optmized into the same cast you have today, so no impacts there.

> >> +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;
> > can this really happen ? why would you receive characters while tty is
> > NULL ?
> 
> Since we are getting a ref to tty - it makes sense to check if the
> pointer is not NULL. Alan had pointed to a possible hangup race which
> could yield a NULL tty. But I'm not really an expert in serial core to
> be sure if at all this will happen - so added the check.

fair enough...

> >> +	/*
> >> +	 * 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;
> >> +}
> > why all these empty functions with wrong comments above them ??
> 
> Copy/paste cruft. Empty functions deleted in next ver !
> Regarding verify_port, I'm not sure whether it needs to elaborately
> check for PORT_UNKNOWN -> PORT_ARC or can we simply continue to return
> 0. But IMHO the comment in there is right. No ?

nope, you say that you should verify the new serial_struct, but you
don't verify anything, just return.

> >> +/*
> >> + * 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;
> >> +}
> >> +
> >> +#if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_ARC_CONSOLE)
> >> +
> >> +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);
> >> +}
> >> +#endif
> >> +
> >> +#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;
> >> +}
> >> +#else
> >> +static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
> >> +{
> >> +	return -ENODEV;
> >> +}
> >> +#endif	/* CONFIG_SERIAL_ARC_CONSOLE */
> >> +
> >> +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");
> > please remove this line, it's just useless IMHO.
> 
> It has helped me enough in past when debugging the uncoupling of driver
> from ARC platform code. I'd rather keep it !

then make it a debugging print ;-)

-- 
balbi

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Re: [PATCH v5] serial/arc-uart: Add new driver

[Vineet Gupta]

On Friday 26 October 2012 05:40 PM, Felipe Balbi wrote:
> On Fri, Oct 26, 2012 at 05:33:16PM +0530, Vineet.Gupta1@synopsys.com wrote:
>> +/*
>> + * 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;
>> +}
> why all these empty functions with wrong comments above them ??

Actually serial_core.c invokes the reqest/release callbacks w/o
verifying for a NULL pointer check. Thus they need to be in there even
if empty. I've removed the offending comments though !

-Vineet

Re: [PATCH v5] serial/arc-uart: Add new driver

[Felipe Balbi]

[-- Attachment #1: Type: text/plain, Size: 1089 bytes --]

On Sat, Oct 27, 2012 at 12:24:46PM +0530, Vineet Gupta wrote:
> On Friday 26 October 2012 05:40 PM, Felipe Balbi wrote:
> > On Fri, Oct 26, 2012 at 05:33:16PM +0530, Vineet.Gupta1@synopsys.com wrote:
> >> +/*
> >> + * 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;
> >> +}
> > why all these empty functions with wrong comments above them ??
> 
> Actually serial_core.c invokes the reqest/release callbacks w/o
> verifying for a NULL pointer check. Thus they need to be in there even
> if empty. I've removed the offending comments though !

fair enough ;-)

-- 
balbi

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Re: [PATCH v5] serial/arc-uart: Add new driver

[Vineet Gupta]

I've already posted a v7 of the driver - with all your comments.
If you think it's ok - can you ACK it please !

TIA,
-Vineet

On Monday 29 October 2012 04:36 PM, Felipe Balbi wrote:
> On Sat, Oct 27, 2012 at 12:24:46PM +0530, Vineet Gupta wrote:
>> On Friday 26 October 2012 05:40 PM, Felipe Balbi wrote:
>>> On Fri, Oct 26, 2012 at 05:33:16PM +0530, Vineet.Gupta1@synopsys.com wrote:
>>>> +/*
>>>> + * 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;
>>>> +}
>>> why all these empty functions with wrong comments above them ??
>> Actually serial_core.c invokes the reqest/release callbacks w/o
>> verifying for a NULL pointer check. Thus they need to be in there even
>> if empty. I've removed the offending comments though !
> fair enough ;-)
>