[ARM] armv6 dcc tty driver

Signed-off-by: Brian Swetland <swetland@google.com>
Signed-off-by: Arve Hjønnevåg <arve@android.com>

3 files changed, 331 insertions, 0 deletions

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 49502bc..b54589e 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -598,6 +598,10 @@ config DEVPORT
 	depends on ISA || PCI
 	default y
 
+config DCC_TTY
+	tristate "DCC tty driver"
+	depends on ARM
+
 source "drivers/s390/char/Kconfig"
 
 config RAMOOPS
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 7a00672..3f63254 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -58,6 +58,7 @@ obj-$(CONFIG_IPMI_HANDLER)	+= ipmi/
 obj-$(CONFIG_HANGCHECK_TIMER)	+= hangcheck-timer.o
 obj-$(CONFIG_TCG_TPM)		+= tpm/
 
+obj-$(CONFIG_DCC_TTY)		+= dcc_tty.o
 obj-$(CONFIG_PS3_FLASH)		+= ps3flash.o
 obj-$(CONFIG_RAMOOPS)		+= ramoops.o
 
diff --git a/drivers/char/dcc_tty.c b/drivers/char/dcc_tty.c
new file mode 100644
index 0000000..a787acc
--- /dev/null
+++ b/drivers/char/dcc_tty.c
@@ -0,0 +1,326 @@
+/* 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);
+
+