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linux/drivers/serial/21285.c
Alan Cox 33f0f88f1c [PATCH] TTY layer buffering revamp 
The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.

This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.

When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.

For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).

Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.

The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.

I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.

Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real.  That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.

Description:

tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification].  It
does now also return the number of chars inserted

There are also

tty_buffer_request_room(tty, len)

which asks for a buffer block of the length requested and returns the space
found.  This improves efficiency with hardware that knows how much to
transfer.

and tty_insert_flip_string_flags(tty, str, flags, len)

to insert a string of characters and flags

For a smart interface the usual code is

    len = tty_request_buffer_room(tty, amount_hardware_says);
    tty_insert_flip_string(tty, buffer_from_card, len);

More description!

At the moment tty buffers are attached directly to the tty.  This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)

I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers.  This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.

So far so good.  Lots of drivers reference tty->flip.*.  Several of them also
call directly and unsafely into function pointers it provides.  This will all
break.  Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.

At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say

 int tty_buffer_request_room(tty, size)

Try and ensure at least size bytes are available, returns actual room (may be
zero).  At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative.  (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space.  The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.

 int tty_insert_flip_char(tty, ch, flag)

As before insert a character if there is room.  Now returns 1 for success, 0
for failure.

 int tty_insert_flip_string(tty, str, len)

Insert a block of non error characters.  Returns the number inserted.

 int tty_prepare_flip_string(tty, strptr, len)

Adjust the buffer to allow len characters to be added.  Returns a buffer
pointer in strptr and the length available.  This allows for hardware that
needs to use functions like insl or mencpy_fromio.

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 08:01:59 -08:00

521 lines
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/*
* linux/drivers/char/21285.c
*
* Driver for the serial port on the 21285 StrongArm-110 core logic chip.
*
* Based on drivers/char/serial.c
*
* $Id: 21285.c,v 1.37 2002/07/28 10:03:27 rmk Exp $
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/device.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/mach-types.h>
#include <asm/hardware/dec21285.h>
#include <asm/hardware.h>
#define BAUD_BASE (mem_fclk_21285/64)
#define SERIAL_21285_NAME "ttyFB"
#define SERIAL_21285_MAJOR 204
#define SERIAL_21285_MINOR 4
#define RXSTAT_DUMMY_READ 0x80000000
#define RXSTAT_FRAME (1 << 0)
#define RXSTAT_PARITY (1 << 1)
#define RXSTAT_OVERRUN (1 << 2)
#define RXSTAT_ANYERR (RXSTAT_FRAME|RXSTAT_PARITY|RXSTAT_OVERRUN)
#define H_UBRLCR_BREAK (1 << 0)
#define H_UBRLCR_PARENB (1 << 1)
#define H_UBRLCR_PAREVN (1 << 2)
#define H_UBRLCR_STOPB (1 << 3)
#define H_UBRLCR_FIFO (1 << 4)
static const char serial21285_name[] = "Footbridge UART";
#define tx_enabled(port) ((port)->unused[0])
#define rx_enabled(port) ((port)->unused[1])
/*
* The documented expression for selecting the divisor is:
* BAUD_BASE / baud - 1
* However, typically BAUD_BASE is not divisible by baud, so
* we want to select the divisor that gives us the minimum
* error. Therefore, we want:
* int(BAUD_BASE / baud - 0.5) ->
* int(BAUD_BASE / baud - (baud >> 1) / baud) ->
* int((BAUD_BASE - (baud >> 1)) / baud)
*/
static void serial21285_stop_tx(struct uart_port *port)
{
if (tx_enabled(port)) {
disable_irq(IRQ_CONTX);
tx_enabled(port) = 0;
}
}
static void serial21285_start_tx(struct uart_port *port)
{
if (!tx_enabled(port)) {
enable_irq(IRQ_CONTX);
tx_enabled(port) = 1;
}
}
static void serial21285_stop_rx(struct uart_port *port)
{
if (rx_enabled(port)) {
disable_irq(IRQ_CONRX);
rx_enabled(port) = 0;
}
}
static void serial21285_enable_ms(struct uart_port *port)
{
}
static irqreturn_t serial21285_rx_chars(int irq, void *dev_id, struct pt_regs *regs)
{
struct uart_port *port = dev_id;
struct tty_struct *tty = port->info->tty;
unsigned int status, ch, flag, rxs, max_count = 256;
status = *CSR_UARTFLG;
while (!(status & 0x10) && max_count--) {
ch = *CSR_UARTDR;
flag = TTY_NORMAL;
port->icount.rx++;
rxs = *CSR_RXSTAT | RXSTAT_DUMMY_READ;
if (unlikely(rxs & RXSTAT_ANYERR)) {
if (rxs & RXSTAT_PARITY)
port->icount.parity++;
else if (rxs & RXSTAT_FRAME)
port->icount.frame++;
if (rxs & RXSTAT_OVERRUN)
port->icount.overrun++;
rxs &= port->read_status_mask;
if (rxs & RXSTAT_PARITY)
flag = TTY_PARITY;
else if (rxs & RXSTAT_FRAME)
flag = TTY_FRAME;
}
uart_insert_char(port, rxs, RXSTAT_OVERRUN, ch, flag);
status = *CSR_UARTFLG;
}
tty_flip_buffer_push(tty);
return IRQ_HANDLED;
}
static irqreturn_t serial21285_tx_chars(int irq, void *dev_id, struct pt_regs *regs)
{
struct uart_port *port = dev_id;
struct circ_buf *xmit = &port->info->xmit;
int count = 256;
if (port->x_char) {
*CSR_UARTDR = port->x_char;
port->icount.tx++;
port->x_char = 0;
goto out;
}
if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
serial21285_stop_tx(port);
goto out;
}
do {
*CSR_UARTDR = 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 && !(*CSR_UARTFLG & 0x20));
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port);
if (uart_circ_empty(xmit))
serial21285_stop_tx(port);
out:
return IRQ_HANDLED;
}
static unsigned int serial21285_tx_empty(struct uart_port *port)
{
return (*CSR_UARTFLG & 8) ? 0 : TIOCSER_TEMT;
}
/* no modem control lines */
static unsigned int serial21285_get_mctrl(struct uart_port *port)
{
return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
}
static void serial21285_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}
static void serial21285_break_ctl(struct uart_port *port, int break_state)
{
unsigned long flags;
unsigned int h_lcr;
spin_lock_irqsave(&port->lock, flags);
h_lcr = *CSR_H_UBRLCR;
if (break_state)
h_lcr |= H_UBRLCR_BREAK;
else
h_lcr &= ~H_UBRLCR_BREAK;
*CSR_H_UBRLCR = h_lcr;
spin_unlock_irqrestore(&port->lock, flags);
}
static int serial21285_startup(struct uart_port *port)
{
int ret;
tx_enabled(port) = 1;
rx_enabled(port) = 1;
ret = request_irq(IRQ_CONRX, serial21285_rx_chars, 0,
serial21285_name, port);
if (ret == 0) {
ret = request_irq(IRQ_CONTX, serial21285_tx_chars, 0,
serial21285_name, port);
if (ret)
free_irq(IRQ_CONRX, port);
}
return ret;
}
static void serial21285_shutdown(struct uart_port *port)
{
free_irq(IRQ_CONTX, port);
free_irq(IRQ_CONRX, port);
}
static void
serial21285_set_termios(struct uart_port *port, struct termios *termios,
struct termios *old)
{
unsigned long flags;
unsigned int baud, quot, h_lcr;
/*
* We don't support modem control lines.
*/
termios->c_cflag &= ~(HUPCL | CRTSCTS | CMSPAR);
termios->c_cflag |= CLOCAL;
/*
* We don't support BREAK character recognition.
*/
termios->c_iflag &= ~(IGNBRK | BRKINT);
/*
* Ask the core to calculate the divisor for us.
*/
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
quot = uart_get_divisor(port, baud);
switch (termios->c_cflag & CSIZE) {
case CS5:
h_lcr = 0x00;
break;
case CS6:
h_lcr = 0x20;
break;
case CS7:
h_lcr = 0x40;
break;
default: /* CS8 */
h_lcr = 0x60;
break;
}
if (termios->c_cflag & CSTOPB)
h_lcr |= H_UBRLCR_STOPB;
if (termios->c_cflag & PARENB) {
h_lcr |= H_UBRLCR_PARENB;
if (!(termios->c_cflag & PARODD))
h_lcr |= H_UBRLCR_PAREVN;
}
if (port->fifosize)
h_lcr |= H_UBRLCR_FIFO;
spin_lock_irqsave(&port->lock, flags);
/*
* Update the per-port timeout.
*/
uart_update_timeout(port, termios->c_cflag, baud);
/*
* Which character status flags are we interested in?
*/
port->read_status_mask = RXSTAT_OVERRUN;
if (termios->c_iflag & INPCK)
port->read_status_mask |= RXSTAT_FRAME | RXSTAT_PARITY;
/*
* Which character status flags should we ignore?
*/
port->ignore_status_mask = 0;
if (termios->c_iflag & IGNPAR)
port->ignore_status_mask |= RXSTAT_FRAME | RXSTAT_PARITY;
if (termios->c_iflag & IGNBRK && termios->c_iflag & IGNPAR)
port->ignore_status_mask |= RXSTAT_OVERRUN;
/*
* Ignore all characters if CREAD is not set.
*/
if ((termios->c_cflag & CREAD) == 0)
port->ignore_status_mask |= RXSTAT_DUMMY_READ;
quot -= 1;
*CSR_UARTCON = 0;
*CSR_L_UBRLCR = quot & 0xff;
*CSR_M_UBRLCR = (quot >> 8) & 0x0f;
*CSR_H_UBRLCR = h_lcr;
*CSR_UARTCON = 1;
spin_unlock_irqrestore(&port->lock, flags);
}
static const char *serial21285_type(struct uart_port *port)
{
return port->type == PORT_21285 ? "DC21285" : NULL;
}
static void serial21285_release_port(struct uart_port *port)
{
release_mem_region(port->mapbase, 32);
}
static int serial21285_request_port(struct uart_port *port)
{
return request_mem_region(port->mapbase, 32, serial21285_name)
!= NULL ? 0 : -EBUSY;
}
static void serial21285_config_port(struct uart_port *port, int flags)
{
if (flags & UART_CONFIG_TYPE && serial21285_request_port(port) == 0)
port->type = PORT_21285;
}
/*
* verify the new serial_struct (for TIOCSSERIAL).
*/
static int serial21285_verify_port(struct uart_port *port, struct serial_struct *ser)
{
int ret = 0;
if (ser->type != PORT_UNKNOWN && ser->type != PORT_21285)
ret = -EINVAL;
if (ser->irq != NO_IRQ)
ret = -EINVAL;
if (ser->baud_base != port->uartclk / 16)
ret = -EINVAL;
return ret;
}
static struct uart_ops serial21285_ops = {
.tx_empty = serial21285_tx_empty,
.get_mctrl = serial21285_get_mctrl,
.set_mctrl = serial21285_set_mctrl,
.stop_tx = serial21285_stop_tx,
.start_tx = serial21285_start_tx,
.stop_rx = serial21285_stop_rx,
.enable_ms = serial21285_enable_ms,
.break_ctl = serial21285_break_ctl,
.startup = serial21285_startup,
.shutdown = serial21285_shutdown,
.set_termios = serial21285_set_termios,
.type = serial21285_type,
.release_port = serial21285_release_port,
.request_port = serial21285_request_port,
.config_port = serial21285_config_port,
.verify_port = serial21285_verify_port,
};
static struct uart_port serial21285_port = {
.mapbase = 0x42000160,
.iotype = SERIAL_IO_MEM,
.irq = NO_IRQ,
.fifosize = 16,
.ops = &serial21285_ops,
.flags = ASYNC_BOOT_AUTOCONF,
};
static void serial21285_setup_ports(void)
{
serial21285_port.uartclk = mem_fclk_21285 / 4;
}
#ifdef CONFIG_SERIAL_21285_CONSOLE
static void
serial21285_console_write(struct console *co, const char *s,
unsigned int count)
{
int i;
for (i = 0; i < count; i++) {
while (*CSR_UARTFLG & 0x20)
barrier();
*CSR_UARTDR = s[i];
if (s[i] == '\n') {
while (*CSR_UARTFLG & 0x20)
barrier();
*CSR_UARTDR = '\r';
}
}
}
static void __init
serial21285_get_options(struct uart_port *port, int *baud,
int *parity, int *bits)
{
if (*CSR_UARTCON == 1) {
unsigned int tmp;
tmp = *CSR_H_UBRLCR;
switch (tmp & 0x60) {
case 0x00:
*bits = 5;
break;
case 0x20:
*bits = 6;
break;
case 0x40:
*bits = 7;
break;
default:
case 0x60:
*bits = 8;
break;
}
if (tmp & H_UBRLCR_PARENB) {
*parity = 'o';
if (tmp & H_UBRLCR_PAREVN)
*parity = 'e';
}
tmp = *CSR_L_UBRLCR | (*CSR_M_UBRLCR << 8);
*baud = port->uartclk / (16 * (tmp + 1));
}
}
static int __init serial21285_console_setup(struct console *co, char *options)
{
struct uart_port *port = &serial21285_port;
int baud = 9600;
int bits = 8;
int parity = 'n';
int flow = 'n';
if (machine_is_personal_server())
baud = 57600;
/*
* Check whether an invalid uart number has been specified, and
* if so, search for the first available port that does have
* console support.
*/
if (options)
uart_parse_options(options, &baud, &parity, &bits, &flow);
else
serial21285_get_options(port, &baud, &parity, &bits);
return uart_set_options(port, co, baud, parity, bits, flow);
}
static struct uart_driver serial21285_reg;
static struct console serial21285_console =
{
.name = SERIAL_21285_NAME,
.write = serial21285_console_write,
.device = uart_console_device,
.setup = serial21285_console_setup,
.flags = CON_PRINTBUFFER,
.index = -1,
.data = &serial21285_reg,
};
static int __init rs285_console_init(void)
{
serial21285_setup_ports();
register_console(&serial21285_console);
return 0;
}
console_initcall(rs285_console_init);
#define SERIAL_21285_CONSOLE &serial21285_console
#else
#define SERIAL_21285_CONSOLE NULL
#endif
static struct uart_driver serial21285_reg = {
.owner = THIS_MODULE,
.driver_name = "ttyFB",
.dev_name = "ttyFB",
.devfs_name = "ttyFB",
.major = SERIAL_21285_MAJOR,
.minor = SERIAL_21285_MINOR,
.nr = 1,
.cons = SERIAL_21285_CONSOLE,
};
static int __init serial21285_init(void)
{
int ret;
printk(KERN_INFO "Serial: 21285 driver $Revision: 1.37 $\n");
serial21285_setup_ports();
ret = uart_register_driver(&serial21285_reg);
if (ret == 0)
uart_add_one_port(&serial21285_reg, &serial21285_port);
return ret;
}
static void __exit serial21285_exit(void)
{
uart_remove_one_port(&serial21285_reg, &serial21285_port);
uart_unregister_driver(&serial21285_reg);
}
module_init(serial21285_init);
module_exit(serial21285_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Intel Footbridge (21285) serial driver $Revision: 1.37 $");
MODULE_ALIAS_CHARDEV(SERIAL_21285_MAJOR, SERIAL_21285_MINOR);
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