Subject: Re: [PATCH] Add support for the nwp serial device

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sun, 23 Nov 2008 09:03:11 +1100

On Thu, 2008-11-20 at 15:01 +0100, Arnd Bergmann wrote:
> From: Benjamin Krill <[email-masked]>
> 
> This patch adds support for the nwp serial device which is connected to
> a DCR bus. It uses the of_serial device driver to determine necessary
> properties from the device tree. The supported device is added as serial
> port number 84.

I don't suppose it would have been useful to at least somewhere mention
what "NWP" serial is and where it can be found ? :-)

Cheers,
Ben.

> Signed-off-by: Benjamin Krill <[email-masked]>
> Signed-off-by: Arnd Bergmann <[email-masked]>
> ---
> 
> Since the serial drivers are still orphaned, should we merge this through
> the powerpc tree?
> 
> ---
>  drivers/serial/Kconfig      |   11 +-
>  drivers/serial/Makefile     |    1 +
>  drivers/serial/nwpserial.c  |  443 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/serial/of_serial.c  |   18 ++
>  include/linux/nwpserial.h   |   18 ++
>  include/linux/serial_core.h |    3 +
>  6 files changed, 493 insertions(+), 1 deletions(-)
>  create mode 100644 drivers/serial/nwpserial.c
>  create mode 100644 include/linux/nwpserial.h
> 
> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
> index 579d63a..45dcc8d 100644
> --- a/drivers/serial/Kconfig
> +++ b/drivers/serial/Kconfig
> @@ -1297,13 +1297,22 @@ config SERIAL_NETX_CONSOLE
>  config SERIAL_OF_PLATFORM
>  	tristate "Serial port on Open Firmware platform bus"
>  	depends on PPC_OF
> -	depends on SERIAL_8250
> +	depends on SERIAL_8250 || SERIAL_OF_PLATFORM_NWPSERIAL
>  	help
>  	  If you have a PowerPC based system that has serial ports
>  	  on a platform specific bus, you should enable this option.
>  	  Currently, only 8250 compatible ports are supported, but
>  	  others can easily be added.
>  
> +config SERIAL_OF_PLATFORM_NWPSERIAL
> +	tristate "NWP serial port driver"
> +	depends on PPC_OF && PPC_DCR
> +	select SERIAL_OF_PLATFORM
> +	select SERIAL_CORE_CONSOLE
> +	select SERIAL_CORE
> +	help
> +	  This driver supports the nwp serial port.
> +
>  config SERIAL_QE
>  	tristate "Freescale QUICC Engine serial port support"
>  	depends on QUICC_ENGINE
> diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
> index 0c17c8d..05da19d 100644
> --- a/drivers/serial/Makefile
> +++ b/drivers/serial/Makefile
> @@ -70,6 +70,7 @@ obj-$(CONFIG_SERIAL_ATMEL) += atmel_serial.o
>  obj-$(CONFIG_SERIAL_UARTLITE) += uartlite.o
>  obj-$(CONFIG_SERIAL_NETX) += netx-serial.o
>  obj-$(CONFIG_SERIAL_OF_PLATFORM) += of_serial.o
> +obj-$(CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL) += nwpserial.o
>  obj-$(CONFIG_SERIAL_KS8695) += serial_ks8695.o
>  obj-$(CONFIG_KGDB_SERIAL_CONSOLE) += kgdboc.o
>  obj-$(CONFIG_SERIAL_QE) += ucc_uart.o
> diff --git a/drivers/serial/nwpserial.c b/drivers/serial/nwpserial.c
> new file mode 100644
> index 0000000..5f2ecab
> --- /dev/null
> +++ b/drivers/serial/nwpserial.c
> @@ -0,0 +1,443 @@
> +/*
> + *  Serial Port driver for a NWP uart device
> + *
> + *    Copyright (C) 2008 IBM Corp., Benjamin Krill <[email-masked]>
> + *
> + *  This program is free software; you can redistribute it and/or
> + *  modify it under the terms of the GNU General Public License
> + *  as published by the Free Software Foundation; either version
> + *  2 of the License, or (at your option) any later version.
> + *
> + */
> +#include <linux/console.h>
> +#include <linux/serial.h>
> +#include <linux/serial_reg.h>
> +#include <linux/serial_core.h>
> +#include <linux/tty.h>
> +#include <linux/irqreturn.h>
> +#include <linux/mutex.h>
> +#include <linux/of_platform.h>
> +#include <linux/of_device.h>
> +#include <linux/nwpserial.h>
> +#include <asm/prom.h>
> +#include <asm/dcr.h>
> +
> +#define NWPSERIAL_NR               2
> +
> +#define NWPSERIAL_STATUS_RXVALID 0x1
> +#define NWPSERIAL_STATUS_TXFULL  0x2
> +
> +struct nwpserial_port {
> +	struct uart_port port;
> +	dcr_host_t dcr_host;
> +	unsigned int ier;
> +	unsigned int mcr;
> +};
> +
> +static DEFINE_MUTEX(nwpserial_mutex);
> +static struct nwpserial_port nwpserial_ports[NWPSERIAL_NR];
> +
> +static void nwpserial_console_putchar(struct uart_port *port, int c)
> +{
> +	struct nwpserial_port *up = container_of(port, struct nwpserial_port, port);
> +	/* check if tx buffer is full */
> +	while ((dcr_read(up->dcr_host, UART_LSR) & UART_LSR_THRE) == 0)
> +		cpu_relax();
> +	dcr_write(up->dcr_host, UART_TX, c);
> +	up->port.icount.tx++;
> +}
> +
> +static void
> +nwpserial_console_write(struct console *co, const char *s, unsigned int count)
> +{
> +	struct nwpserial_port *up = &nwpserial_ports[co->index];
> +	unsigned long flags;
> +	int locked = 1;
> +
> +	if (oops_in_progress)
> +		locked = spin_trylock_irqsave(&up->port.lock, flags);
> +	else
> +		spin_lock_irqsave(&up->port.lock, flags);
> +
> +	/* save and disable interrupt */
> +	up->ier = dcr_read(up->dcr_host, UART_IER);
> +	dcr_write(up->dcr_host, UART_IER, up->ier & ~UART_IER_RDI);
> +
> +	uart_console_write(&up->port, s, count, nwpserial_console_putchar);
> +
> +	/* wait for transmitter to become emtpy */
> +	while ((dcr_read(up->dcr_host, UART_LSR) & UART_LSR_THRE) == 0)
> +		cpu_relax();
> +
> +	/* restore interrupt state */
> +	dcr_write(up->dcr_host, UART_IER, up->ier);
> +
> +	if (locked)
> +		spin_unlock_irqrestore(&up->port.lock, flags);
> +}
> +
> +static struct uart_driver nwpserial_reg;
> +static struct console nwpserial_console = {
> +	.name		= "ttySQ",
> +	.write		= nwpserial_console_write,
> +	.device		= uart_console_device,
> +	.flags		= CON_PRINTBUFFER,
> +	.index		= -1,
> +	.data		= &nwpserial_reg,
> +};
> +
> +/*******************************************************************************/
> +
> +static int nwpserial_request_port(struct uart_port *port)
> +{
> +	return 0;
> +}
> +
> +static void nwpserial_release_port(struct uart_port *port)
> +{
> +	/* N/A */
> +}
> +
> +static void nwpserial_config_port(struct uart_port *port, int flags)
> +{
> +	port->type = PORT_NWPSERIAL;
> +}
> +
> +static irqreturn_t nwpserial_interrupt(int irq, void *dev_id)
> +{
> +	struct nwpserial_port *up = dev_id;//container_of(dev_id, struct nwpserial_port, port);
> +	struct tty_struct *tty = up->port.info->port.tty;
> +	irqreturn_t ret;
> +	unsigned int iir;
> +	unsigned char ch;
> +
> +	spin_lock(&up->port.lock);
> +
> +	/* check if the uart was the interrupt source. */
> +	iir = dcr_read(up->dcr_host, UART_IIR);
> +	if (!iir) {
> +		ret = IRQ_NONE;
> +		goto out;
> +	}
> +
> +	do {
> +		up->port.icount.rx++;
> +		ch = dcr_read(up->dcr_host, UART_RX);
> +		if (up->port.ignore_status_mask != NWPSERIAL_STATUS_RXVALID)
> +			tty_insert_flip_char(tty, ch, TTY_NORMAL);
> +	} while (dcr_read(up->dcr_host, UART_RX) & UART_LSR_DR);
> +
> +	tty_flip_buffer_push(tty);
> +	ret = IRQ_HANDLED;
> +
> +out:
> +	spin_unlock(&up->port.lock);
> +	return ret;
> +}
> +
> +static int nwpserial_startup(struct uart_port *port)
> +{
> +	struct nwpserial_port *up = container_of(port, struct nwpserial_port, port);
> +	int err;
> +
> +	/* disable flow control by default */
> +	up->mcr = dcr_read(up->dcr_host, UART_MCR) & ~UART_MCR_AFE;
> +	dcr_write(up->dcr_host, UART_MCR, up->mcr);
> +
> +	/* register interrupt handler */
> +	err = request_irq(up->port.irq, nwpserial_interrupt,
> +	                        IRQF_SHARED, "nwpserial", up);
> +	if (err) {
> +		free_irq(up->port.irq, port);
> +		return err;
> +	}
> +
> +	/* enable interrupts */
> +	up->ier = UART_IER_RDI;
> +	dcr_write(up->dcr_host, UART_IER, up->ier);
> +
> +	/* enable receiving */
> +	up->port.ignore_status_mask &= ~NWPSERIAL_STATUS_RXVALID;
> +
> +	return 0;
> +}
> +
> +static void nwpserial_shutdown(struct uart_port *port)
> +{
> +	struct nwpserial_port *up = container_of(port, struct nwpserial_port, port);
> +
> +	/* disable receiving */
> +	up->port.ignore_status_mask |= NWPSERIAL_STATUS_RXVALID;
> +
> +	/* disable interrupts from this port */
> +	up->ier = 0;
> +	dcr_write(up->dcr_host, UART_IER, up->ier);
> +
> +	/* free irq */
> +	free_irq(up->port.irq, port);
> +}
> +
> +static int nwpserial_verify_port(struct uart_port *port, struct serial_struct *ser)
> +{
> +	return -EINVAL;
> +}
> +
> +static const char *nwpserial_type(struct uart_port *port)
> +{
> +	return port->type == PORT_NWPSERIAL ? "nwpserial" : NULL;
> +}
> +
> +static void nwpserial_set_termios(struct uart_port *port, struct ktermios *termios,
> +                                struct ktermios *old)
> +{
> +	struct nwpserial_port *up = container_of(port, struct nwpserial_port, port);
> +
> +	up->port.read_status_mask = NWPSERIAL_STATUS_RXVALID | NWPSERIAL_STATUS_TXFULL;
> +
> +	up->port.ignore_status_mask = 0;
> +	/* ignore all characters if CREAD is not set */
> +	if ((termios->c_cflag & CREAD) == 0)
> +		up->port.ignore_status_mask |= NWPSERIAL_STATUS_RXVALID;
> +}
> +
> +static void nwpserial_break_ctl(struct uart_port *port, int ctl)
> +{
> +	/* N/A */
> +}
> +
> +static void nwpserial_enable_ms(struct uart_port *port)
> +{
> +	/* N/A */
> +}
> +
> +static void nwpserial_stop_rx(struct uart_port *port)
> +{
> +	struct nwpserial_port *up = container_of(port, struct nwpserial_port, port);
> +	/* don't forward any more data (like !CREAD) */
> +	up->port.ignore_status_mask = NWPSERIAL_STATUS_RXVALID;
> +}
> +
> +static void nwpserial_putchar(struct nwpserial_port *up, unsigned char c)
> +{
> +	/* check if tx buffer is full */
> +	while ((dcr_read(up->dcr_host, UART_LSR) & UART_LSR_THRE) == 0)
> +		cpu_relax();
> +	dcr_write(up->dcr_host, UART_TX, c);
> +	up->port.icount.tx++;
> +}
> +
> +static void nwpserial_start_tx(struct uart_port *port)
> +{
> +	struct nwpserial_port *up = container_of(port, struct nwpserial_port, port);
> +	struct circ_buf *xmit  = &up->port.info->xmit;
> +
> +	if (port->x_char) {
> +		nwpserial_putchar(up, up->port.x_char);
> +		port->x_char = 0;
> +	}
> +
> +	while (!(uart_circ_empty(xmit) || uart_tx_stopped(&up->port))) {
> +		nwpserial_putchar(up, xmit->buf[xmit->tail]);
> +		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE-1);
> +	}
> +}
> +
> +static unsigned int nwpserial_get_mctrl(struct uart_port *port)
> +{
> +	return 0;
> +}
> +
> +static void nwpserial_set_mctrl(struct uart_port *port, unsigned int mctrl)
> +{
> +	/* N/A */
> +}
> +
> +static void nwpserial_stop_tx(struct uart_port *port)
> +{
> +	/* N/A */
> +}
> +
> +static unsigned int nwpserial_tx_empty(struct uart_port *port)
> +{
> +	struct nwpserial_port *up = container_of(port, struct nwpserial_port, port);
> +	unsigned long flags;
> +	int ret;
> +
> +	spin_lock_irqsave(&up->port.lock, flags);
> +	ret = dcr_read(up->dcr_host, UART_LSR);
> +	spin_unlock_irqrestore(&up->port.lock, flags);
> +
> +	return ret & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
> +}
> +
> +static struct uart_ops nwpserial_pops = {
> +	.tx_empty     = nwpserial_tx_empty,
> +	.set_mctrl    = nwpserial_set_mctrl,
> +	.get_mctrl    = nwpserial_get_mctrl,
> +	.stop_tx      = nwpserial_stop_tx,
> +	.start_tx     = nwpserial_start_tx,
> +	.stop_rx      = nwpserial_stop_rx,
> +	.enable_ms    = nwpserial_enable_ms,
> +	.break_ctl    = nwpserial_break_ctl,
> +	.startup      = nwpserial_startup,
> +	.shutdown     = nwpserial_shutdown,
> +	.set_termios  = nwpserial_set_termios,
> +	.type         = nwpserial_type,
> +	.release_port = nwpserial_release_port,
> +	.request_port = nwpserial_request_port,
> +	.config_port  = nwpserial_config_port,
> +	.verify_port  = nwpserial_verify_port,
> +};
> +
> +static struct uart_driver nwpserial_reg = {
> +	.owner       = THIS_MODULE,
> +	.driver_name = "nwpserial",
> +	.dev_name    = "ttySQ",
> +	.major       = TTY_MAJOR,
> +	.minor       = 68,
> +	.nr          = NWPSERIAL_NR,
> +	.cons        = &nwpserial_console,
> +};
> +
> +int
> +nwpserial_register_port(struct uart_port *port)
> +{
> +	struct nwpserial_port *up = NULL;
> +	int ret = -1;
> +	int i;
> +	static int first = 1;
> +	int dcr_len;
> +	int dcr_base;
> +	struct device_node *dn;
> +
> +	mutex_lock(&nwpserial_mutex);
> +
> +	dn = to_of_device(port->dev)->node;
> +	if (dn == NULL)
> +		goto out;
> +
> +	/* get dcr base. */
> +	dcr_base = dcr_resource_start(dn, 0);
> +
> +	/* find matching entry */
> +	for (i = 0; i < NWPSERIAL_NR; i++)
> +		if (nwpserial_ports[i].port.iobase == dcr_base) {
> +			up = &nwpserial_ports[i];
> +			break;
> +		}
> +
> +	/* we didn't find a mtching entry, search for a free port */
> +	if (up == NULL)
> +		for (i = 0; i < NWPSERIAL_NR; i++)
> +			if (nwpserial_ports[i].port.type == PORT_UNKNOWN &&
> +				nwpserial_ports[i].port.iobase == 0) {
> +				up = &nwpserial_ports[i];
> +				break;
> +			}
> +
> +	if (up == NULL) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	if (first)
> +		uart_register_driver(&nwpserial_reg);
> +	first = 0;
> +
> +	up->port.membase      = port->membase;
> +	up->port.irq          = port->irq;
> +	up->port.uartclk      = port->uartclk;
> +	up->port.fifosize     = port->fifosize;
> +	up->port.regshift     = port->regshift;
> +	up->port.iotype       = port->iotype;
> +	up->port.flags        = port->flags;
> +	up->port.mapbase      = port->mapbase;
> +	up->port.private_data = port->private_data;
> +
> +	if (port->dev)
> +		up->port.dev = port->dev;
> +
> +	if (up->port.iobase != dcr_base) {
> +		up->port.ops          = &nwpserial_pops;
> +		up->port.fifosize     = 16;
> +
> +		spin_lock_init(&up->port.lock);
> +
> +		up->port.iobase = dcr_base;
> +		dcr_len = dcr_resource_len(dn, 0);
> +
> +		up->dcr_host = dcr_map(dn, dcr_base, dcr_len);
> +		if (!DCR_MAP_OK(up->dcr_host)) {
> +			printk("Cannot map DCR resources for NWPSERIAL");
> +			goto out;
> +		}
> +	}
> +
> +	ret = uart_add_one_port(&nwpserial_reg, &up->port);
> +	if (ret == 0)
> +		ret = up->port.line;
> +
> +out:
> +	mutex_unlock(&nwpserial_mutex);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(nwpserial_register_port);
> +
> +void nwpserial_unregister_port(int line)
> +{
> +	struct nwpserial_port *up = &nwpserial_ports[line];
> +	mutex_lock(&nwpserial_mutex);
> +	uart_remove_one_port(&nwpserial_reg, &up->port);
> +
> +	up->port.type = PORT_UNKNOWN;
> +
> +	mutex_unlock(&nwpserial_mutex);
> +}
> +EXPORT_SYMBOL(nwpserial_unregister_port);
> +
> +static int __init nwpserial_console_init(void)
> +{
> +	struct nwpserial_port *up = NULL;
> +	struct device_node *dn;
> +	const char *name;
> +	int dcr_base;
> +	int dcr_len;
> +	int i;
> +
> +	/* search for a free port */
> +	for (i = 0; i < NWPSERIAL_NR; i++)
> +		if (nwpserial_ports[i].port.type == PORT_UNKNOWN) {
> +			up = &nwpserial_ports[i];
> +			break;
> +		}
> +
> +	if (up == NULL)
> +		return -1;
> +
> +	name = of_get_property(of_chosen, "linux,stdout-path", NULL);
> +	if (name == NULL)
> +		return -1;
> +
> +	dn = of_find_node_by_path(name);
> +	if (!dn)
> +		return -1;
> +
> +	spin_lock_init(&up->port.lock);
> +	up->port.ops = &nwpserial_pops;
> +	up->port.type = PORT_NWPSERIAL;
> +	up->port.fifosize = 16;
> +
> +	dcr_base = dcr_resource_start(dn, 0);
> +	dcr_len = dcr_resource_len(dn, 0);
> +	up->port.iobase = dcr_base;
> +
> +	up->dcr_host = dcr_map(dn, dcr_base, dcr_len);
> +	if (!DCR_MAP_OK(up->dcr_host)) {
> +		printk("Cannot map DCR resources for SERIAL");
> +		return -1;
> +	}
> +	register_console(&nwpserial_console);
> +	return 0;
> +}
> +console_initcall(nwpserial_console_init);
> diff --git a/drivers/serial/of_serial.c b/drivers/serial/of_serial.c
> index 8fa0ff5..bb56231 100644
> --- a/drivers/serial/of_serial.c
> +++ b/drivers/serial/of_serial.c
> @@ -14,6 +14,7 @@
>  #include <linux/serial_core.h>
>  #include <linux/serial_8250.h>
>  #include <linux/of_platform.h>
> +#include <linux/nwpserial.h>
>  
>  #include <asm/prom.h>
>  
> @@ -99,9 +100,16 @@ static int __devinit of_platform_serial_probe(struct of_device *ofdev,
>  		goto out;
>  
>  	switch (port_type) {
> +#ifdef CONFIG_SERIAL_8250
>  	case PORT_8250 ... PORT_MAX_8250:
>  		ret = serial8250_register_port(&port);
>  		break;
> +#endif
> +#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL
> +	case PORT_NWPSERIAL:
> +		ret = nwpserial_register_port(&port);
> +		break;
> +#endif
>  	default:
>  		/* need to add code for these */
>  	case PORT_UNKNOWN:
> @@ -129,9 +137,16 @@ static int of_platform_serial_remove(struct of_device *ofdev)
>  {
>  	struct of_serial_info *info = ofdev->dev.driver_data;
>  	switch (info->type) {
> +#ifdef CONFIG_SERIAL_8250
>  	case PORT_8250 ... PORT_MAX_8250:
>  		serial8250_unregister_port(info->line);
>  		break;
> +#endif
> +#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL
> +	case PORT_NWPSERIAL:
> +		nwpserial_unregister_port(info->line);
> +		break;
> +#endif
>  	default:
>  		/* need to add code for these */
>  		break;
> @@ -148,6 +163,9 @@ static struct of_device_id __devinitdata of_platform_serial_table[] = {
>  	{ .type = "serial", .compatible = "ns16450",  .data = (void *)PORT_16450, },
>  	{ .type = "serial", .compatible = "ns16550",  .data = (void *)PORT_16550, },
>  	{ .type = "serial", .compatible = "ns16750",  .data = (void *)PORT_16750, },
> +#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL
> +	{ .type = "serial", .compatible = "ibm,qpace-nwpserial",  .data = (void *)PORT_NWPSERIAL, },
> +#endif
>  	{ .type = "serial",			      .data = (void *)PORT_UNKNOWN, },
>  	{ /* end of list */ },
>  };
> diff --git a/include/linux/nwpserial.h b/include/linux/nwpserial.h
> new file mode 100644
> index 0000000..9acb215
> --- /dev/null
> +++ b/include/linux/nwpserial.h
> @@ -0,0 +1,18 @@
> +/*
> + *  Serial Port driver for a NWP uart device
> + *
> + *    Copyright (C) 2008 IBM Corp., Benjamin Krill <[email-masked]>
> + *
> + *  This program is free software; you can redistribute it and/or
> + *  modify it under the terms of the GNU General Public License
> + *  as published by the Free Software Foundation; either version
> + *  2 of the License, or (at your option) any later version.
> + *
> + */
> +#ifndef _NWPSERIAL_H
> +#define _NWPSERIAL_H
> +
> +int nwpserial_register_port(struct uart_port *port);
> +void nwpserial_unregister_port(int line);
> +
> +#endif /* _NWPSERIAL_H */
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 4e4f127..4621faf 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -158,6 +158,9 @@
>  /* SH-SCI */
>  #define PORT_SCIFA	83
>  
> +/* NWPSERIAL */
> +#define PORT_NWPSERIAL	84
> +
>  #ifdef __KERNEL__
>  
>  #include <linux/compiler.h>