--- /dev/null
+/* 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>
+
+MODULE_DESCRIPTION("DCC TTY Driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0");
+
+static spinlock_t g_dcc_tty_lock = SPIN_LOCK_UNLOCKED;
+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);
+
+
projects / firefly-linux-kernel-4.4.55.git / commitdiff