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@xxxxxxxxxxxx wrote:
>> From: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>>
>> Driver for non-standard on-chip UART, instantiated in the ARC (Synopsys)
>> FPGA Boards such as ARCAngel4/ML50x
>>
>> Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>> ---
>>  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
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