/*
* dashtty.c - tty driver for Dash channels interface.
*
* Copyright (C) 2007,2008,2012 Imagination Technologies
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of this archive
* for more details.
*
*/
#include <linux/atomic.h>
#include <linux/completion.h>
#include <linux/console.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/moduleparam.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/serial.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/uaccess.h>
#include <asm/da.h>
/* Channel error codes */
#define CONAOK 0
#define CONERR 1
#define CONBAD 2
#define CONPRM 3
#define CONADR 4
#define CONCNT 5
#define CONCBF 6
#define CONCBE 7
#define CONBSY 8
/* Default channel for the console */
#define CONSOLE_CHANNEL 1
#define NUM_TTY_CHANNELS 6
/* Auto allocate */
#define DA_TTY_MAJOR 0
/* A speedy poll rate helps the userland debug process connection response.
* But, if you set it too high then no other userland processes get much
* of a look in.
*/
#define DA_TTY_POLL (HZ / 50)
/*
* A short put delay improves latency but has a high throughput overhead
*/
#define DA_TTY_PUT_DELAY (HZ / 100)
static atomic_t num_channels_need_poll = ATOMIC_INIT(0);
static struct timer_list poll_timer;
static struct tty_driver *channel_driver;
static struct timer_list put_timer;
static struct task_struct *dashtty_thread;
/*
* The console_poll parameter determines whether the console channel should be
* polled for input.
* By default the console channel isn't polled at all, in order to avoid the
* overhead, but that means it isn't possible to have a login on /dev/console.
*/
static bool console_poll;
module_param(console_poll, bool, S_IRUGO);
#define RX_BUF_SIZE 1024
enum {
INCHR = 1,
OUTCHR,
RDBUF,
WRBUF,
RDSTAT
};
/**
* struct dashtty_port - Wrapper struct for dashtty tty_port.
* @port: TTY port data
* @rx_lock: Lock for rx_buf.
* This protects between the poll timer and user context.
* It's also held during read SWITCH operations.
* @rx_buf: Read buffer
* @xmit_lock: Lock for xmit_*, and port.xmit_buf.
* This protects between user context and kernel thread.
* It's also held during write SWITCH operations.
* @xmit_cnt: Size of xmit buffer contents
* @xmit_head: Head of xmit buffer where data is written
* @xmit_tail: Tail of xmit buffer where data is read
* @xmit_empty: Completion for xmit buffer being empty
*/
struct dashtty_port {
struct tty_port port;
spinlock_t rx_lock;
void *rx_buf;
struct mutex xmit_lock;
unsigned int xmit_cnt;
unsigned int xmit_head;
unsigned int xmit_tail;
struct completion xmit_empty;
};
static struct dashtty_port dashtty_ports[NUM_TTY_CHANNELS];
static atomic_t dashtty_xmit_cnt = ATOMIC_INIT(0);
static wait_queue_head_t dashtty_waitqueue;
/*
* Low-level DA channel access routines
*/
static int chancall(int in_bios_function, int in_channel,
int in_arg2, void *in_arg3,
void *in_arg4)
{
register int bios_function asm("D1Ar1") = in_bios_function;
register int channel asm("D0Ar2") = in_channel;
register int arg2 asm("D1Ar3") = in_arg2;
register void *arg3 asm("D0Ar4") = in_arg3;
register void *arg4 asm("D1Ar5") = in_arg4;
register int bios_call asm("D0Ar6") = 3;
register int result asm("D0Re0");
asm volatile (
"MSETL [A0StP++], %6,%4,%2\n\t"
"ADD A0StP, A0StP, #8\n\t"
"SWITCH #0x0C30208\n\t"
"GETD %0, [A0StP+#-8]\n\t"
"SUB A0StP, A0StP, #(4*6)+8\n\t"
: "=d" (result) /* outs */
: "d" (bios_function),
"d" (channel),
"d" (arg2),
"d" (arg3),
"d" (arg4),
"d" (bios_call) /* ins */
: "memory");
return result;
}
/*
* Attempts to fetch count bytes from channel and returns actual count.
*/
static int fetch_data(unsigned int channel)
{
struct dashtty_port *dport = &dashtty_ports[channel];
int received = 0;
spin_lock_bh(&dport->rx_lock);
/* check the port isn't being shut down */
if (!dport->rx_buf)
goto unlock;
if (chancall(RDBUF, channel, RX_BUF_SIZE,
(void *)dport->rx_buf, &received) == CONAOK) {
if (received) {
int space;
unsigned char *cbuf;
space = tty_prepare_flip_string(&dport->port, &cbuf,
received);
if (space <= 0)
goto unlock;
memcpy(cbuf, dport->rx_buf, space);
tty_flip_buffer_push(&dport->port);
}
}
unlock:
spin_unlock_bh(&dport->rx_lock);
return received;
}
/**
* find_channel_to_poll() - Returns number of the next channel to poll.
* Returns: The number of the next channel to poll, or -1 if none need
* polling.
*/
static int find_channel_to_poll(void)
{
static int last_polled_channel;
int last = last_polled_channel;
int chan;
struct dashtty_port *dport;
for (chan = last + 1; ; ++chan) {
if (chan >= NUM_TTY_CHANNELS)
chan = 0;
dport = &dashtty_ports[chan];
if (dport->rx_buf) {
last_polled_channel = chan;
return chan;
}
if (chan == last)
break;
}
return -1;
}
/**
* put_channel_data() - Write out a block of channel data.
* @chan: DA channel number.
*
* Write a single block of data out to the debug adapter. If the circular buffer
* is wrapped then only the first block is written.
*
* Returns: 1 if the remote buffer was too full to accept data.
* 0 otherwise.
*/
static int put_channel_data(unsigned int chan)
{
struct dashtty_port *dport;
struct tty_struct *tty;
int number_written;
unsigned int count = 0;
dport = &dashtty_ports[chan];
mutex_lock(&dport->xmit_lock);
if (dport->xmit_cnt) {
count = min((unsigned int)(SERIAL_XMIT_SIZE - dport->xmit_tail),
dport->xmit_cnt);
chancall(WRBUF, chan, count,
dport->port.xmit_buf + dport->xmit_tail,
&number_written);
dport->xmit_cnt -= number_written;
if (!dport->xmit_cnt) {
/* reset pointers to avoid wraps */
dport->xmit_head = 0;
dport->xmit_tail = 0;
complete(&dport->xmit_empty);
} else {
dport->xmit_tail += number_written;
if (dport->xmit_tail >= SERIAL_XMIT_SIZE)
dport->xmit_tail -= SERIAL_XMIT_SIZE;
}
atomic_sub(number_written, &dashtty_xmit_cnt);
}
mutex_unlock(&dport->xmit_lock);
/* if we've made more data available, wake up tty */
if (count && number_written) {
tty = tty_port_tty_get(&dport->port);
if (tty) {
tty_wakeup(tty);
tty_kref_put(tty);
}
}
/* did the write fail? */
return count && !number_written;
}
/**
* put_data() - Kernel thread to write out blocks of channel data to DA.
* @arg: Unused.
*
* This kernel thread runs while @dashtty_xmit_cnt != 0, and loops over the
* channels to write out any buffered data. If any of the channels stall due to
* the remote buffer being full, a hold off happens to allow the debugger to
* drain the buffer.
*/
static int put_data(void *arg)
{
unsigned int chan, stall;
__set_current_state(TASK_RUNNING);
while (!kthread_should_stop()) {
/*
* For each channel see if there's anything to transmit in the
* port's xmit_buf.
*/
stall = 0;
for (chan = 0; chan < NUM_TTY_CHANNELS; ++chan)
stall += put_channel_data(chan);
/*
* If some of the buffers are full, hold off for a short while
* to allow them to empty.
*/
if (stall)
msleep(25);
wait_event_interruptible(dashtty_waitqueue,
atomic_read(&dashtty_xmit_cnt));
}
return 0;
}
/*
* This gets called every DA_TTY_POLL and polls the channels for data
*/
static void dashtty_timer(unsigned long ignored)
{
int channel;
/* If there are no ports open do nothing and don't poll again. */
if (!atomic_read(&num_channels_need_poll))
return;
channel = find_channel_to_poll();
/* Did we find a channel to poll? */
if (channel >= 0)
fetch_data(channel);
mod_timer(&poll_timer, jiffies + DA_TTY_POLL);
}
static void add_poll_timer(struct timer_list *poll_timer)
{
setup_pinned_timer(poll_timer, dashtty_timer, 0);
poll_timer->expires = jiffies + DA_TTY_POLL;
/*
* Always attach the timer to the boot CPU. The DA channels are per-CPU
* so all polling should be from a single CPU.
*/
add_timer_on(poll_timer, 0);
}
static int dashtty_port_activate(struct tty_port *port, struct tty_struct *tty)
{
struct dashtty_port *dport = container_of(port, struct dashtty_port,
port);
void *rx_buf;
/* Allocate the buffer we use for writing data */
if (tty_port_alloc_xmit_buf(port) < 0)
goto err;
/* Allocate the buffer we use for reading data */
rx_buf = kzalloc(RX_BUF_SIZE, GFP_KERNEL);
if (!rx_buf)
goto err_free_xmit;
spin_lock_bh(&dport->rx_lock);
dport->rx_buf = rx_buf;
spin_unlock_bh(&dport->rx_lock);
/*
* Don't add the poll timer if we're opening a console. This
* avoids the overhead of polling the Dash but means it is not
* possible to have a login on /dev/console.
*
*/
if (console_poll || dport != &dashtty_ports[CONSOLE_CHANNEL])
if (atomic_inc_return(&num_channels_need_poll) == 1)
add_poll_timer(&poll_timer);
return 0;
err_free_xmit:
tty_port_free_xmit_buf(port);
err:
return -ENOMEM;
}
static void dashtty_port_shutdown(struct tty_port *port)
{
struct dashtty_port *dport = container_of(port, struct dashtty_port,
port);
void *rx_buf;
unsigned int count;
/* stop reading */
if (console_poll || dport != &dashtty_ports[CONSOLE_CHANNEL])
if (atomic_dec_and_test(&num_channels_need_poll))
del_timer_sync(&poll_timer);
mutex_lock(&dport->xmit_lock);
count = dport->xmit_cnt;
mutex_unlock(&dport->xmit_lock);
if (count) {
/*
* There's still data to write out, so wake and wait for the
* writer thread to drain the buffer.
*/
del_timer(&put_timer);
wake_up_interruptible(&dashtty_waitqueue);
wait_for_completion(&dport->xmit_empty);
}
/* Null the read buffer (timer could still be running!) */
spin_lock_bh(&dport->rx_lock);
rx_buf = dport->rx_buf;
dport->rx_buf = NULL;
spin_unlock_bh(&dport->rx_lock);
/* Free the read buffer */
kfree(rx_buf);
/* Free the write buffer */
tty_port_free_xmit_buf(port);
}
static const struct tty_port_operations dashtty_port_ops = {
.activate = dashtty_port_activate,
.shutdown = dashtty_port_shutdown,
};
static int dashtty_install(struct tty_driver *driver, struct tty_struct *tty)
{
return tty_port_install(&dashtty_ports[tty->index].port, driver, tty);
}
static int dashtty_open(struct tty_struct *tty, struct file *filp)
{
return tty_port_open(tty->port, tty, filp);
}
static void dashtty_close(struct tty_struct *tty, struct file *filp)
{
return tty_port_close(tty->port, tty, filp);
}
static void dashtty_hangup(struct tty_struct *tty)
{
int channel;
struct dashtty_port *dport;
channel = tty->index;
dport = &dashtty_ports[channel];
/* drop any data in the xmit buffer */
mutex_lock(&dport->xmit_lock);
if (dport->xmit_cnt) {
atomic_sub(dport->xmit_cnt, &dashtty_xmit_cnt);
dport->xmit_cnt = 0;
dport->xmit_head = 0;
dport->xmit_tail = 0;
complete(&dport->xmit_empty);
}
mutex_unlock(&dport->xmit_lock);
tty_port_hangup(tty->port);
}
/**
* dashtty_put_timer() - Delayed wake up of kernel thread.
* @ignored: unused
*
* This timer function wakes up the kernel thread if any data exists in the
* buffers. It is used to delay the expensive writeout until the writer has
* stopped writing.
*/
static void dashtty_put_timer(unsigned long ignored)
{
if (atomic_read(&dashtty_xmit_cnt))
wake_up_interruptible(&dashtty_waitqueue);
}
static int dashtty_write(struct tty_struct *tty, const unsigned char *buf,
int total)
{
int channel, count, block;
struct dashtty_port *dport;
/* Determine the channel */
channel = tty->index;
dport = &dashtty_ports[channel];
/*
* Write to output buffer.
*
* The reason that we asynchronously write the buffer is because if we
* were to write the buffer synchronously then because DA channels are
* per-CPU the buffer would be written to the channel of whatever CPU
* we're running on.
*
* What we actually want to happen is have all input and output done on
* one CPU.
*/
mutex_lock(&dport->xmit_lock);
/* work out how many bytes we can write to the xmit buffer */
total = min(total, (int)(SERIAL_XMIT_SIZE - dport->xmit_cnt));
atomic_add(total, &dashtty_xmit_cnt);
dport->xmit_cnt += total;
/* write the actual bytes (may need splitting if it wraps) */
for (count = total; count; count -= block) {
block = min(count, (int)(SERIAL_XMIT_SIZE - dport->xmit_head));
memcpy(dport->port.xmit_buf + dport->xmit_head, buf, block);
dport->xmit_head += block;
if (dport->xmit_head >= SERIAL_XMIT_SIZE)
dport->xmit_head -= SERIAL_XMIT_SIZE;
buf += block;
}
count = dport->xmit_cnt;
/* xmit buffer no longer empty? */
if (count)
reinit_completion(&dport->xmit_empty);
mutex_unlock(&dport->xmit_lock);
if (total) {
/*
* If the buffer is full, wake up the kthread, otherwise allow
* some more time for the buffer to fill up a bit before waking
* it.
*/
if (count == SERIAL_XMIT_SIZE) {
del_timer(&put_timer);
wake_up_interruptible(&dashtty_waitqueue);
} else {
mod_timer(&put_timer, jiffies + DA_TTY_PUT_DELAY);
}
}
return total;
}
static int dashtty_write_room(struct tty_struct *tty)
{
struct dashtty_port *dport;
int channel;
int room;
channel = tty->index;
dport = &dashtty_ports[channel];
/* report the space in the xmit buffer */
mutex_lock(&dport->xmit_lock);
room = SERIAL_XMIT_SIZE - dport->xmit_cnt;
mutex_unlock(&dport->xmit_lock);
return room;
}
static int dashtty_chars_in_buffer(struct tty_struct *tty)
{
struct dashtty_port *dport;
int channel;
int chars;
channel = tty->index;
dport = &dashtty_ports[channel];
/* report the number of bytes in the xmit buffer */
mutex_lock(&dport->xmit_lock);
chars = dport->xmit_cnt;
mutex_unlock(&dport->xmit_lock);
return chars;
}
static const struct tty_operations dashtty_ops = {
.install = dashtty_install,
.open = dashtty_open,
.close = dashtty_close,
.hangup = dashtty_hangup,
.write = dashtty_write,
.write_room = dashtty_write_room,
.chars_in_buffer = dashtty_chars_in_buffer,
};
static int __init dashtty_init(void)
{
int ret;
int nport;
struct dashtty_port *dport;
if (!metag_da_enabled())
return -ENODEV;
channel_driver = tty_alloc_driver(NUM_TTY_CHANNELS,
TTY_DRIVER_REAL_RAW);
if (IS_ERR(channel_driver))
return PTR_ERR(channel_driver);
channel_driver->driver_name = "metag_da";
channel_driver->name = "ttyDA";
channel_driver->major = DA_TTY_MAJOR;
channel_driver->minor_start = 0;
channel_driver->type = TTY_DRIVER_TYPE_SERIAL;
channel_driver->subtype = SERIAL_TYPE_NORMAL;
channel_driver->init_termios = tty_std_termios;
channel_driver->init_termios.c_cflag |= CLOCAL;
tty_set_operations(channel_driver, &dashtty_ops);
for (nport = 0; nport < NUM_TTY_CHANNELS; nport++) {
dport = &dashtty_ports[nport];
tty_port_init(&dport->port);
dport->port.ops = &dashtty_port_ops;
spin_lock_init(&dport->rx_lock);
mutex_init(&dport->xmit_lock);
/* the xmit buffer starts empty, i.e. completely written */
init_completion(&dport->xmit_empty);
complete(&dport->xmit_empty);
}
setup_timer(&put_timer, dashtty_put_timer, 0);
init_waitqueue_head(&dashtty_waitqueue);
dashtty_thread = kthread_create(put_data, NULL, "ttyDA");
if (IS_ERR(dashtty_thread)) {
pr_err("Couldn't create dashtty thread\n");
ret = PTR_ERR(dashtty_thread);
goto err_destroy_ports;
}
/*
* Bind the writer thread to the boot CPU so it can't migrate.
* DA channels are per-CPU and we want all channel I/O to be on a single
* predictable CPU.
*/
kthread_bind(dashtty_thread, 0);
wake_up_process(dashtty_thread);
ret = tty_register_driver(channel_driver);
if (ret < 0) {
pr_err("Couldn't install dashtty driver: err %d\n",
ret);
goto err_stop_kthread;
}
return 0;
err_stop_kthread:
kthread_stop(dashtty_thread);
err_destroy_ports:
for (nport = 0; nport < NUM_TTY_CHANNELS; nport++) {
dport = &dashtty_ports[nport];
tty_port_destroy(&dport->port);
}
put_tty_driver(channel_driver);
return ret;
}
device_initcall(dashtty_init);
#ifdef [31mCONFIG_DA_CONSOLE[0m
static void dash_console_write(struct console *co, const char *s,
unsigned int count)
{
int actually_written;
chancall(WRBUF, CONSOLE_CHANNEL, count, (void *)s, &actually_written);
}
static struct tty_driver *dash_console_device(struct console *c, int *index)
{
*index = c->index;
return channel_driver;
}
struct console dash_console = {
.name = "ttyDA",
.write = dash_console_write,
.device = dash_console_device,
.flags = CON_PRINTBUFFER,
.index = 1,
};
#endif