blob: 7643f50d527199150abd464b7a793064c0684e61 [file] [log] [blame]
/* drivers/char/dcc_tty.c
*
* Copyright (C) 2007 Google, Inc.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/console.h>
#include <linux/hrtimer.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/spinlock.h>
MODULE_DESCRIPTION("DCC TTY Driver");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.0");
static spinlock_t g_dcc_tty_lock = __SPIN_LOCK_UNLOCKED(g_dcc_tty_lock);
static struct hrtimer g_dcc_timer;
static char g_dcc_buffer[16];
static int g_dcc_buffer_head;
static int g_dcc_buffer_count;
static unsigned g_dcc_write_delay_usecs = 1;
static struct tty_driver *g_dcc_tty_driver;
static struct tty_struct *g_dcc_tty;
static int g_dcc_tty_open_count;
static void dcc_poll_locked(void)
{
char ch;
int rch;
int written;
while (g_dcc_buffer_count) {
ch = g_dcc_buffer[g_dcc_buffer_head];
asm(
"mrc 14, 0, r15, c0, c1, 0\n"
"mcrcc 14, 0, %1, c0, c5, 0\n"
"movcc %0, #1\n"
"movcs %0, #0\n"
: "=r" (written)
: "r" (ch)
);
if (written) {
if (ch == '\n')
g_dcc_buffer[g_dcc_buffer_head] = '\r';
else {
g_dcc_buffer_head = (g_dcc_buffer_head + 1) % ARRAY_SIZE(g_dcc_buffer);
g_dcc_buffer_count--;
if (g_dcc_tty)
tty_wakeup(g_dcc_tty);
}
g_dcc_write_delay_usecs = 1;
} else {
if (g_dcc_write_delay_usecs > 0x100)
break;
g_dcc_write_delay_usecs <<= 1;
udelay(g_dcc_write_delay_usecs);
}
}
if (g_dcc_tty && !test_bit(TTY_THROTTLED, &g_dcc_tty->flags)) {
asm(
"mrc 14, 0, %0, c0, c1, 0\n"
"tst %0, #(1 << 30)\n"
"moveq %0, #-1\n"
"mrcne 14, 0, %0, c0, c5, 0\n"
: "=r" (rch)
);
if (rch >= 0) {
ch = rch;
tty_insert_flip_string(g_dcc_tty, &ch, 1);
tty_flip_buffer_push(g_dcc_tty);
}
}
if (g_dcc_buffer_count)
hrtimer_start(&g_dcc_timer, ktime_set(0, g_dcc_write_delay_usecs * NSEC_PER_USEC), HRTIMER_MODE_REL);
else
hrtimer_start(&g_dcc_timer, ktime_set(0, 20 * NSEC_PER_MSEC), HRTIMER_MODE_REL);
}
static int dcc_tty_open(struct tty_struct * tty, struct file * filp)
{
int ret;
unsigned long irq_flags;
spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
if (g_dcc_tty == NULL || g_dcc_tty == tty) {
g_dcc_tty = tty;
g_dcc_tty_open_count++;
ret = 0;
} else
ret = -EBUSY;
spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
printk("dcc_tty_open, tty %p, f_flags %x, returned %d\n", tty, filp->f_flags, ret);
return ret;
}
static void dcc_tty_close(struct tty_struct * tty, struct file * filp)
{
printk("dcc_tty_close, tty %p, f_flags %x\n", tty, filp->f_flags);
if (g_dcc_tty == tty) {
if (--g_dcc_tty_open_count == 0)
g_dcc_tty = NULL;
}
}
static int dcc_write(const unsigned char *buf_start, int count)
{
const unsigned char *buf = buf_start;
unsigned long irq_flags;
int copy_len;
int space_left;
int tail;
if (count < 1)
return 0;
spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
do {
tail = (g_dcc_buffer_head + g_dcc_buffer_count) % ARRAY_SIZE(g_dcc_buffer);
copy_len = ARRAY_SIZE(g_dcc_buffer) - tail;
space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
if (copy_len > space_left)
copy_len = space_left;
if (copy_len > count)
copy_len = count;
memcpy(&g_dcc_buffer[tail], buf, copy_len);
g_dcc_buffer_count += copy_len;
buf += copy_len;
count -= copy_len;
if (copy_len < count && copy_len < space_left) {
space_left -= copy_len;
copy_len = count;
if (copy_len > space_left) {
copy_len = space_left;
}
memcpy(g_dcc_buffer, buf, copy_len);
buf += copy_len;
count -= copy_len;
g_dcc_buffer_count += copy_len;
}
dcc_poll_locked();
space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
} while(count && space_left);
spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
return buf - buf_start;
}
static int dcc_tty_write(struct tty_struct * tty, const unsigned char *buf, int count)
{
int ret;
/* printk("dcc_tty_write %p, %d\n", buf, count); */
ret = dcc_write(buf, count);
if (ret != count)
printk("dcc_tty_write %p, %d, returned %d\n", buf, count, ret);
return ret;
}
static int dcc_tty_write_room(struct tty_struct *tty)
{
int space_left;
unsigned long irq_flags;
spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
space_left = ARRAY_SIZE(g_dcc_buffer) - g_dcc_buffer_count;
spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
return space_left;
}
static int dcc_tty_chars_in_buffer(struct tty_struct *tty)
{
int ret;
asm(
"mrc 14, 0, %0, c0, c1, 0\n"
"mov %0, %0, LSR #30\n"
"and %0, %0, #1\n"
: "=r" (ret)
);
return ret;
}
static void dcc_tty_unthrottle(struct tty_struct * tty)
{
unsigned long irq_flags;
spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
dcc_poll_locked();
spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
}
static enum hrtimer_restart dcc_tty_timer_func(struct hrtimer *timer)
{
unsigned long irq_flags;
spin_lock_irqsave(&g_dcc_tty_lock, irq_flags);
dcc_poll_locked();
spin_unlock_irqrestore(&g_dcc_tty_lock, irq_flags);
return HRTIMER_NORESTART;
}
void dcc_console_write(struct console *co, const char *b, unsigned count)
{
#if 1
dcc_write(b, count);
#else
/* blocking printk */
while (count > 0) {
int written;
written = dcc_write(b, count);
if (written) {
b += written;
count -= written;
}
}
#endif
}
static struct tty_driver *dcc_console_device(struct console *c, int *index)
{
*index = 0;
return g_dcc_tty_driver;
}
static int __init dcc_console_setup(struct console *co, char *options)
{
if (co->index != 0)
return -ENODEV;
return 0;
}
static struct console dcc_console =
{
.name = "ttyDCC",
.write = dcc_console_write,
.device = dcc_console_device,
.setup = dcc_console_setup,
.flags = CON_PRINTBUFFER,
.index = -1,
};
static struct tty_operations dcc_tty_ops = {
.open = dcc_tty_open,
.close = dcc_tty_close,
.write = dcc_tty_write,
.write_room = dcc_tty_write_room,
.chars_in_buffer = dcc_tty_chars_in_buffer,
.unthrottle = dcc_tty_unthrottle,
};
static int __init dcc_tty_init(void)
{
int ret;
hrtimer_init(&g_dcc_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
g_dcc_timer.function = dcc_tty_timer_func;
g_dcc_tty_driver = alloc_tty_driver(1);
if (!g_dcc_tty_driver) {
printk(KERN_ERR "dcc_tty_probe: alloc_tty_driver failed\n");
ret = -ENOMEM;
goto err_alloc_tty_driver_failed;
}
g_dcc_tty_driver->owner = THIS_MODULE;
g_dcc_tty_driver->driver_name = "dcc";
g_dcc_tty_driver->name = "ttyDCC";
g_dcc_tty_driver->major = 0; // auto assign
g_dcc_tty_driver->minor_start = 0;
g_dcc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
g_dcc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
g_dcc_tty_driver->init_termios = tty_std_termios;
g_dcc_tty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
tty_set_operations(g_dcc_tty_driver, &dcc_tty_ops);
ret = tty_register_driver(g_dcc_tty_driver);
if (ret) {
printk(KERN_ERR "dcc_tty_probe: tty_register_driver failed, %d\n", ret);
goto err_tty_register_driver_failed;
}
tty_register_device(g_dcc_tty_driver, 0, NULL);
register_console(&dcc_console);
hrtimer_start(&g_dcc_timer, ktime_set(0, 0), HRTIMER_MODE_REL);
return 0;
err_tty_register_driver_failed:
put_tty_driver(g_dcc_tty_driver);
g_dcc_tty_driver = NULL;
err_alloc_tty_driver_failed:
return ret;
}
static void __exit dcc_tty_exit(void)
{
int ret;
tty_unregister_device(g_dcc_tty_driver, 0);
ret = tty_unregister_driver(g_dcc_tty_driver);
if (ret < 0) {
printk(KERN_ERR "dcc_tty_remove: tty_unregister_driver failed, %d\n", ret);
} else {
put_tty_driver(g_dcc_tty_driver);
}
g_dcc_tty_driver = NULL;
}
module_init(dcc_tty_init);
module_exit(dcc_tty_exit);