kernel-ark/drivers/serial/mux.c
Ryan Bradetich a137ce8536 [PARISC] Define port->timeout to fix a long msleep in mux.c
This commit is in response to a bug reported by Vesa on the irc channel
a couple of weeks ago.

The bug was that the console would apparently hang (not return) while
using the mux console.

The root cause of this bug is that bash (with readline support) makes a
call to the tcsetattr() glibc function with the argument TCSADRAIN.  This
causes the serial core in the kernel use the uart_wait_until_sent() to be
called. This function verifies the mux transmit queue is empty or calls the
msleep_interruptable() with a calculated timeout value that is dependant
upon the port->timeout variable.

The real problem here is that the port->timeout was not defined so it
was defaulted to 0 and the timeout calculation performs the following
calculation:

char_time = (port->timeout - HZ/50) / port->fifosize;

where char_time is an unsigned long. Since the serial Mux does not use
interrupts, the msleep_interruptable() function waits until the timeout
has been reached ... and when the port->timeout < HZ/50 this timeout will
be a long time. (I have validated that the console will eventually
return ... but it takes quite a while for this to happen).

This patch simply sets the port->timeout on the Mux to HZ/50 to avoid
this long timeout period.

Signed-off-by: Ryan Bradetich <rbrad@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
2005-11-17 16:38:28 -05:00

544 lines
12 KiB
C

/*
** mux.c:
** serial driver for the Mux console found in some PA-RISC servers.
**
** (c) Copyright 2002 Ryan Bradetich
** (c) Copyright 2002 Hewlett-Packard Company
**
** 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.
**
** This Driver currently only supports the console (port 0) on the MUX.
** Additional work will be needed on this driver to enable the full
** functionality of the MUX.
**
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/serial.h>
#include <linux/console.h>
#include <linux/slab.h>
#include <linux/delay.h> /* for udelay */
#include <linux/device.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/parisc-device.h>
#ifdef CONFIG_MAGIC_SYSRQ
#include <linux/sysrq.h>
#define SUPPORT_SYSRQ
#endif
#include <linux/serial_core.h>
#define MUX_OFFSET 0x800
#define MUX_LINE_OFFSET 0x80
#define MUX_FIFO_SIZE 255
#define MUX_POLL_DELAY (30 * HZ / 1000)
#define IO_DATA_REG_OFFSET 0x3c
#define IO_DCOUNT_REG_OFFSET 0x40
#define MUX_EOFIFO(status) ((status & 0xF000) == 0xF000)
#define MUX_STATUS(status) ((status & 0xF000) == 0x8000)
#define MUX_BREAK(status) ((status & 0xF000) == 0x2000)
#define MUX_NR 256
static unsigned int port_cnt = 0;
static struct uart_port mux_ports[MUX_NR];
static struct uart_driver mux_driver = {
.owner = THIS_MODULE,
.driver_name = "ttyB",
.dev_name = "ttyB",
.major = MUX_MAJOR,
.minor = 0,
.nr = MUX_NR,
};
static struct timer_list mux_timer;
#define UART_PUT_CHAR(p, c) __raw_writel((c), (p)->membase + IO_DATA_REG_OFFSET)
#define UART_GET_FIFO_CNT(p) __raw_readl((p)->membase + IO_DCOUNT_REG_OFFSET)
#define GET_MUX_PORTS(iodc_data) ((((iodc_data)[4] & 0xf0) >> 4) * 8) + 8
/**
* mux_tx_empty - Check if the transmitter fifo is empty.
* @port: Ptr to the uart_port.
*
* This function test if the transmitter fifo for the port
* described by 'port' is empty. If it is empty, this function
* should return TIOCSER_TEMT, otherwise return 0.
*/
static unsigned int mux_tx_empty(struct uart_port *port)
{
return UART_GET_FIFO_CNT(port) ? 0 : TIOCSER_TEMT;
}
/**
* mux_set_mctrl - Set the current state of the modem control inputs.
* @ports: Ptr to the uart_port.
* @mctrl: Modem control bits.
*
* The Serial MUX does not support CTS, DCD or DSR so this function
* is ignored.
*/
static void mux_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}
/**
* mux_get_mctrl - Returns the current state of modem control inputs.
* @port: Ptr to the uart_port.
*
* The Serial MUX does not support CTS, DCD or DSR so these lines are
* treated as permanently active.
*/
static unsigned int mux_get_mctrl(struct uart_port *port)
{
return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
}
/**
* mux_stop_tx - Stop transmitting characters.
* @port: Ptr to the uart_port.
*
* The Serial MUX does not support this function.
*/
static void mux_stop_tx(struct uart_port *port)
{
}
/**
* mux_start_tx - Start transmitting characters.
* @port: Ptr to the uart_port.
*
* The Serial Mux does not support this function.
*/
static void mux_start_tx(struct uart_port *port)
{
}
/**
* mux_stop_rx - Stop receiving characters.
* @port: Ptr to the uart_port.
*
* The Serial Mux does not support this function.
*/
static void mux_stop_rx(struct uart_port *port)
{
}
/**
* mux_enable_ms - Enable modum status interrupts.
* @port: Ptr to the uart_port.
*
* The Serial Mux does not support this function.
*/
static void mux_enable_ms(struct uart_port *port)
{
}
/**
* mux_break_ctl - Control the transmitssion of a break signal.
* @port: Ptr to the uart_port.
* @break_state: Raise/Lower the break signal.
*
* The Serial Mux does not support this function.
*/
static void mux_break_ctl(struct uart_port *port, int break_state)
{
}
/**
* mux_write - Write chars to the mux fifo.
* @port: Ptr to the uart_port.
*
* This function writes all the data from the uart buffer to
* the mux fifo.
*/
static void mux_write(struct uart_port *port)
{
int count;
struct circ_buf *xmit = &port->info->xmit;
if(port->x_char) {
UART_PUT_CHAR(port, port->x_char);
port->icount.tx++;
port->x_char = 0;
return;
}
if(uart_circ_empty(xmit) || uart_tx_stopped(port)) {
mux_stop_tx(port);
return;
}
count = (port->fifosize) - UART_GET_FIFO_CNT(port);
do {
UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
port->icount.tx++;
if(uart_circ_empty(xmit))
break;
} while(--count > 0);
while(UART_GET_FIFO_CNT(port))
udelay(1);
if(uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port);
if (uart_circ_empty(xmit))
mux_stop_tx(port);
}
/**
* mux_read - Read chars from the mux fifo.
* @port: Ptr to the uart_port.
*
* This reads all available data from the mux's fifo and pushes
* the data to the tty layer.
*/
static void mux_read(struct uart_port *port)
{
int data;
struct tty_struct *tty = port->info->tty;
__u32 start_count = port->icount.rx;
while(1) {
data = __raw_readl(port->membase + IO_DATA_REG_OFFSET);
if (MUX_STATUS(data))
continue;
if (MUX_EOFIFO(data))
break;
if (tty->flip.count >= TTY_FLIPBUF_SIZE)
continue;
*tty->flip.char_buf_ptr = data & 0xffu;
*tty->flip.flag_buf_ptr = TTY_NORMAL;
port->icount.rx++;
if (MUX_BREAK(data)) {
port->icount.brk++;
if(uart_handle_break(port))
continue;
}
if (uart_handle_sysrq_char(port, data & 0xffu, NULL))
continue;
tty->flip.flag_buf_ptr++;
tty->flip.char_buf_ptr++;
tty->flip.count++;
}
if (start_count != port->icount.rx) {
tty_flip_buffer_push(tty);
}
}
/**
* mux_startup - Initialize the port.
* @port: Ptr to the uart_port.
*
* Grab any resources needed for this port and start the
* mux timer.
*/
static int mux_startup(struct uart_port *port)
{
mod_timer(&mux_timer, jiffies + MUX_POLL_DELAY);
return 0;
}
/**
* mux_shutdown - Disable the port.
* @port: Ptr to the uart_port.
*
* Release any resources needed for the port.
*/
static void mux_shutdown(struct uart_port *port)
{
}
/**
* mux_set_termios - Chane port parameters.
* @port: Ptr to the uart_port.
* @termios: new termios settings.
* @old: old termios settings.
*
* The Serial Mux does not support this function.
*/
static void
mux_set_termios(struct uart_port *port, struct termios *termios,
struct termios *old)
{
}
/**
* mux_type - Describe the port.
* @port: Ptr to the uart_port.
*
* Return a pointer to a string constant describing the
* specified port.
*/
static const char *mux_type(struct uart_port *port)
{
return "Mux";
}
/**
* mux_release_port - Release memory and IO regions.
* @port: Ptr to the uart_port.
*
* Release any memory and IO region resources currently in use by
* the port.
*/
static void mux_release_port(struct uart_port *port)
{
}
/**
* mux_request_port - Request memory and IO regions.
* @port: Ptr to the uart_port.
*
* Request any memory and IO region resources required by the port.
* If any fail, no resources should be registered when this function
* returns, and it should return -EBUSY on failure.
*/
static int mux_request_port(struct uart_port *port)
{
return 0;
}
/**
* mux_config_port - Perform port autoconfiguration.
* @port: Ptr to the uart_port.
* @type: Bitmask of required configurations.
*
* Perform any autoconfiguration steps for the port. This functino is
* called if the UPF_BOOT_AUTOCONF flag is specified for the port.
* [Note: This is required for now because of a bug in the Serial core.
* rmk has already submitted a patch to linus, should be available for
* 2.5.47.]
*/
static void mux_config_port(struct uart_port *port, int type)
{
port->type = PORT_MUX;
}
/**
* mux_verify_port - Verify the port information.
* @port: Ptr to the uart_port.
* @ser: Ptr to the serial information.
*
* Verify the new serial port information contained within serinfo is
* suitable for this port type.
*/
static int mux_verify_port(struct uart_port *port, struct serial_struct *ser)
{
if(port->membase == NULL)
return -EINVAL;
return 0;
}
/**
* mux_drv_poll - Mux poll function.
* @unused: Unused variable
*
* This function periodically polls the Serial MUX to check for new data.
*/
static void mux_poll(unsigned long unused)
{
int i;
for(i = 0; i < port_cnt; ++i) {
if(!mux_ports[i].info)
continue;
mux_read(&mux_ports[i]);
mux_write(&mux_ports[i]);
}
mod_timer(&mux_timer, jiffies + MUX_POLL_DELAY);
}
#ifdef CONFIG_SERIAL_MUX_CONSOLE
static void mux_console_write(struct console *co, const char *s, unsigned count)
{
while(count--)
pdc_iodc_putc(*s++);
}
static int mux_console_setup(struct console *co, char *options)
{
return 0;
}
struct tty_driver *mux_console_device(struct console *co, int *index)
{
*index = co->index;
return mux_driver.tty_driver;
}
static struct console mux_console = {
.name = "ttyB",
.write = mux_console_write,
.device = mux_console_device,
.setup = mux_console_setup,
.flags = CON_ENABLED | CON_PRINTBUFFER,
.index = 0,
};
#define MUX_CONSOLE &mux_console
#else
#define MUX_CONSOLE NULL
#endif
static struct uart_ops mux_pops = {
.tx_empty = mux_tx_empty,
.set_mctrl = mux_set_mctrl,
.get_mctrl = mux_get_mctrl,
.stop_tx = mux_stop_tx,
.start_tx = mux_start_tx,
.stop_rx = mux_stop_rx,
.enable_ms = mux_enable_ms,
.break_ctl = mux_break_ctl,
.startup = mux_startup,
.shutdown = mux_shutdown,
.set_termios = mux_set_termios,
.type = mux_type,
.release_port = mux_release_port,
.request_port = mux_request_port,
.config_port = mux_config_port,
.verify_port = mux_verify_port,
};
/**
* mux_probe - Determine if the Serial Mux should claim this device.
* @dev: The parisc device.
*
* Deterimine if the Serial Mux should claim this chip (return 0)
* or not (return 1).
*/
static int __init mux_probe(struct parisc_device *dev)
{
int i, status, ports;
u8 iodc_data[32];
unsigned long bytecnt;
struct uart_port *port;
status = pdc_iodc_read(&bytecnt, dev->hpa.start, 0, iodc_data, 32);
if(status != PDC_OK) {
printk(KERN_ERR "Serial mux: Unable to read IODC.\n");
return 1;
}
ports = GET_MUX_PORTS(iodc_data);
printk(KERN_INFO "Serial mux driver (%d ports) Revision: 0.3\n", ports);
if(!port_cnt) {
mux_driver.cons = MUX_CONSOLE;
status = uart_register_driver(&mux_driver);
if(status) {
printk(KERN_ERR "Serial mux: Unable to register driver.\n");
return 1;
}
init_timer(&mux_timer);
mux_timer.function = mux_poll;
}
for(i = 0; i < ports; ++i, ++port_cnt) {
port = &mux_ports[port_cnt];
port->iobase = 0;
port->mapbase = dev->hpa.start + MUX_OFFSET +
(i * MUX_LINE_OFFSET);
port->membase = ioremap(port->mapbase, MUX_LINE_OFFSET);
port->iotype = SERIAL_IO_MEM;
port->type = PORT_MUX;
port->irq = NO_IRQ;
port->uartclk = 0;
port->fifosize = MUX_FIFO_SIZE;
port->ops = &mux_pops;
port->flags = UPF_BOOT_AUTOCONF;
port->line = port_cnt;
/* The port->timeout needs to match what is present in
* uart_wait_until_sent in serial_core.c. Otherwise
* the time spent in msleep_interruptable will be very
* long, causing the appearance of a console hang.
*/
port->timeout = HZ / 50;
spin_lock_init(&port->lock);
status = uart_add_one_port(&mux_driver, port);
BUG_ON(status);
}
#ifdef CONFIG_SERIAL_MUX_CONSOLE
register_console(&mux_console);
#endif
return 0;
}
static struct parisc_device_id mux_tbl[] = {
{ HPHW_A_DIRECT, HVERSION_REV_ANY_ID, HVERSION_ANY_ID, 0x0000D },
{ 0, }
};
MODULE_DEVICE_TABLE(parisc, mux_tbl);
static struct parisc_driver serial_mux_driver = {
.name = "serial_mux",
.id_table = mux_tbl,
.probe = mux_probe,
};
/**
* mux_init - Serial MUX initalization procedure.
*
* Register the Serial MUX driver.
*/
static int __init mux_init(void)
{
return register_parisc_driver(&serial_mux_driver);
}
/**
* mux_exit - Serial MUX cleanup procedure.
*
* Unregister the Serial MUX driver from the tty layer.
*/
static void __exit mux_exit(void)
{
int i;
for (i = 0; i < port_cnt; i++) {
uart_remove_one_port(&mux_driver, &mux_ports[i]);
}
uart_unregister_driver(&mux_driver);
}
module_init(mux_init);
module_exit(mux_exit);
MODULE_AUTHOR("Ryan Bradetich");
MODULE_DESCRIPTION("Serial MUX driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_CHARDEV_MAJOR(MUX_MAJOR);