tty: bfin_jtag_comm: emulate a TTY over the Blackfin EMUDAT/JTAG interface
The Blackfin JTAG interface has a 4 byte generic data field (EMUDAT). With
a little creative thinking, we can turn this into a TTY device.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/bfin_jtag_comm.c b/drivers/char/bfin_jtag_comm.c
new file mode 100644
index 0000000..44c113d
--- /dev/null
+++ b/drivers/char/bfin_jtag_comm.c
@@ -0,0 +1,365 @@
+/*
+ * TTY over Blackfin JTAG Communication
+ *
+ * Copyright 2008-2009 Analog Devices Inc.
+ *
+ * Enter bugs at http://blackfin.uclinux.org/
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/circ_buf.h>
+#include <linux/console.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <asm/atomic.h>
+
+/* See the Debug/Emulation chapter in the HRM */
+#define EMUDOF 0x00000001 /* EMUDAT_OUT full & valid */
+#define EMUDIF 0x00000002 /* EMUDAT_IN full & valid */
+#define EMUDOOVF 0x00000004 /* EMUDAT_OUT overflow */
+#define EMUDIOVF 0x00000008 /* EMUDAT_IN overflow */
+
+#define DRV_NAME "bfin-jtag-comm"
+#define DEV_NAME "ttyBFJC"
+
+#define pr_init(fmt, args...) ({ static const __initdata char __fmt[] = fmt; printk(__fmt, ## args); })
+#define debug(fmt, args...) pr_debug(DRV_NAME ": " fmt, ## args)
+
+static inline uint32_t bfin_write_emudat(uint32_t emudat)
+{
+ __asm__ __volatile__("emudat = %0;" : : "d"(emudat));
+ return emudat;
+}
+
+static inline uint32_t bfin_read_emudat(void)
+{
+ uint32_t emudat;
+ __asm__ __volatile__("%0 = emudat;" : "=d"(emudat));
+ return emudat;
+}
+
+static inline uint32_t bfin_write_emudat_chars(char a, char b, char c, char d)
+{
+ return bfin_write_emudat((a << 0) | (b << 8) | (c << 16) | (d << 24));
+}
+
+#define CIRC_SIZE 2048 /* see comment in tty_io.c:do_tty_write() */
+#define CIRC_MASK (CIRC_SIZE - 1)
+#define circ_empty(circ) ((circ)->head == (circ)->tail)
+#define circ_free(circ) CIRC_SPACE((circ)->head, (circ)->tail, CIRC_SIZE)
+#define circ_cnt(circ) CIRC_CNT((circ)->head, (circ)->tail, CIRC_SIZE)
+#define circ_byte(circ, idx) ((circ)->buf[(idx) & CIRC_MASK])
+
+static struct tty_driver *bfin_jc_driver;
+static struct task_struct *bfin_jc_kthread;
+static struct tty_struct * volatile bfin_jc_tty;
+static unsigned long bfin_jc_count;
+static DEFINE_MUTEX(bfin_jc_tty_mutex);
+static volatile struct circ_buf bfin_jc_write_buf;
+
+static int
+bfin_jc_emudat_manager(void *arg)
+{
+ uint32_t inbound_len = 0, outbound_len = 0;
+
+ while (!kthread_should_stop()) {
+ /* no one left to give data to, so sleep */
+ if (bfin_jc_tty == NULL && circ_empty(&bfin_jc_write_buf)) {
+ debug("waiting for readers\n");
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule();
+ __set_current_state(TASK_RUNNING);
+ }
+
+ /* no data available, so just chill */
+ if (!(bfin_read_DBGSTAT() & EMUDIF) && circ_empty(&bfin_jc_write_buf)) {
+ debug("waiting for data (in_len = %i) (circ: %i %i)\n",
+ inbound_len, bfin_jc_write_buf.tail, bfin_jc_write_buf.head);
+ if (inbound_len)
+ schedule();
+ else
+ schedule_timeout_interruptible(HZ);
+ continue;
+ }
+
+ /* if incoming data is ready, eat it */
+ if (bfin_read_DBGSTAT() & EMUDIF) {
+ struct tty_struct *tty;
+ mutex_lock(&bfin_jc_tty_mutex);
+ tty = (struct tty_struct *)bfin_jc_tty;
+ if (tty != NULL) {
+ uint32_t emudat = bfin_read_emudat();
+ if (inbound_len == 0) {
+ debug("incoming length: 0x%08x\n", emudat);
+ inbound_len = emudat;
+ } else {
+ size_t num_chars = (4 <= inbound_len ? 4 : inbound_len);
+ debug(" incoming data: 0x%08x (pushing %zu)\n", emudat, num_chars);
+ inbound_len -= num_chars;
+ tty_insert_flip_string(tty, (unsigned char *)&emudat, num_chars);
+ tty_flip_buffer_push(tty);
+ }
+ }
+ mutex_unlock(&bfin_jc_tty_mutex);
+ }
+
+ /* if outgoing data is ready, post it */
+ if (!(bfin_read_DBGSTAT() & EMUDOF) && !circ_empty(&bfin_jc_write_buf)) {
+ if (outbound_len == 0) {
+ outbound_len = circ_cnt(&bfin_jc_write_buf);
+ bfin_write_emudat(outbound_len);
+ debug("outgoing length: 0x%08x\n", outbound_len);
+ } else {
+ struct tty_struct *tty;
+ int tail = bfin_jc_write_buf.tail;
+ size_t ate = (4 <= outbound_len ? 4 : outbound_len);
+ uint32_t emudat =
+ bfin_write_emudat_chars(
+ circ_byte(&bfin_jc_write_buf, tail + 0),
+ circ_byte(&bfin_jc_write_buf, tail + 1),
+ circ_byte(&bfin_jc_write_buf, tail + 2),
+ circ_byte(&bfin_jc_write_buf, tail + 3)
+ );
+ bfin_jc_write_buf.tail += ate;
+ outbound_len -= ate;
+ mutex_lock(&bfin_jc_tty_mutex);
+ tty = (struct tty_struct *)bfin_jc_tty;
+ if (tty)
+ tty_wakeup(tty);
+ mutex_unlock(&bfin_jc_tty_mutex);
+ debug(" outgoing data: 0x%08x (pushing %zu)\n", emudat, ate);
+ }
+ }
+ }
+
+ __set_current_state(TASK_RUNNING);
+ return 0;
+}
+
+static int
+bfin_jc_open(struct tty_struct *tty, struct file *filp)
+{
+ mutex_lock(&bfin_jc_tty_mutex);
+ debug("open %lu\n", bfin_jc_count);
+ ++bfin_jc_count;
+ bfin_jc_tty = tty;
+ wake_up_process(bfin_jc_kthread);
+ mutex_unlock(&bfin_jc_tty_mutex);
+ return 0;
+}
+
+static void
+bfin_jc_close(struct tty_struct *tty, struct file *filp)
+{
+ mutex_lock(&bfin_jc_tty_mutex);
+ debug("close %lu\n", bfin_jc_count);
+ if (--bfin_jc_count == 0)
+ bfin_jc_tty = NULL;
+ wake_up_process(bfin_jc_kthread);
+ mutex_unlock(&bfin_jc_tty_mutex);
+}
+
+/* XXX: we dont handle the put_char() case where we must handle count = 1 */
+static int
+bfin_jc_circ_write(const unsigned char *buf, int count)
+{
+ int i;
+ count = min(count, circ_free(&bfin_jc_write_buf));
+ debug("going to write chunk of %i bytes\n", count);
+ for (i = 0; i < count; ++i)
+ circ_byte(&bfin_jc_write_buf, bfin_jc_write_buf.head + i) = buf[i];
+ bfin_jc_write_buf.head += i;
+ return i;
+}
+
+#ifndef CONFIG_BFIN_JTAG_COMM_CONSOLE
+# define acquire_console_sem()
+# define release_console_sem()
+#endif
+static int
+bfin_jc_write(struct tty_struct *tty, const unsigned char *buf, int count)
+{
+ int i;
+ acquire_console_sem();
+ i = bfin_jc_circ_write(buf, count);
+ release_console_sem();
+ wake_up_process(bfin_jc_kthread);
+ return i;
+}
+
+static void
+bfin_jc_flush_chars(struct tty_struct *tty)
+{
+ wake_up_process(bfin_jc_kthread);
+}
+
+static int
+bfin_jc_write_room(struct tty_struct *tty)
+{
+ return circ_free(&bfin_jc_write_buf);
+}
+
+static int
+bfin_jc_chars_in_buffer(struct tty_struct *tty)
+{
+ return circ_cnt(&bfin_jc_write_buf);
+}
+
+static void
+bfin_jc_wait_until_sent(struct tty_struct *tty, int timeout)
+{
+ unsigned long expire = jiffies + timeout;
+ while (!circ_empty(&bfin_jc_write_buf)) {
+ if (signal_pending(current))
+ break;
+ if (time_after(jiffies, expire))
+ break;
+ }
+}
+
+static struct tty_operations bfin_jc_ops = {
+ .open = bfin_jc_open,
+ .close = bfin_jc_close,
+ .write = bfin_jc_write,
+ /*.put_char = bfin_jc_put_char,*/
+ .flush_chars = bfin_jc_flush_chars,
+ .write_room = bfin_jc_write_room,
+ .chars_in_buffer = bfin_jc_chars_in_buffer,
+ .wait_until_sent = bfin_jc_wait_until_sent,
+};
+
+static int __init bfin_jc_init(void)
+{
+ int ret;
+
+ bfin_jc_kthread = kthread_create(bfin_jc_emudat_manager, NULL, DRV_NAME);
+ if (IS_ERR(bfin_jc_kthread))
+ return PTR_ERR(bfin_jc_kthread);
+
+ ret = -ENOMEM;
+
+ bfin_jc_write_buf.head = bfin_jc_write_buf.tail = 0;
+ bfin_jc_write_buf.buf = kmalloc(CIRC_SIZE, GFP_KERNEL);
+ if (!bfin_jc_write_buf.buf)
+ goto err;
+
+ bfin_jc_driver = alloc_tty_driver(1);
+ if (!bfin_jc_driver)
+ goto err;
+
+ bfin_jc_driver->owner = THIS_MODULE;
+ bfin_jc_driver->driver_name = DRV_NAME;
+ bfin_jc_driver->name = DEV_NAME;
+ bfin_jc_driver->type = TTY_DRIVER_TYPE_SERIAL;
+ bfin_jc_driver->subtype = SERIAL_TYPE_NORMAL;
+ bfin_jc_driver->init_termios = tty_std_termios;
+ tty_set_operations(bfin_jc_driver, &bfin_jc_ops);
+
+ ret = tty_register_driver(bfin_jc_driver);
+ if (ret)
+ goto err;
+
+ pr_init(KERN_INFO DRV_NAME ": initialized\n");
+
+ return 0;
+
+ err:
+ put_tty_driver(bfin_jc_driver);
+ kfree(bfin_jc_write_buf.buf);
+ kthread_stop(bfin_jc_kthread);
+ return ret;
+}
+module_init(bfin_jc_init);
+
+static void __exit bfin_jc_exit(void)
+{
+ kthread_stop(bfin_jc_kthread);
+ kfree(bfin_jc_write_buf.buf);
+ tty_unregister_driver(bfin_jc_driver);
+ put_tty_driver(bfin_jc_driver);
+}
+module_exit(bfin_jc_exit);
+
+#if defined(CONFIG_BFIN_JTAG_COMM_CONSOLE) || defined(CONFIG_EARLY_PRINTK)
+static void
+bfin_jc_straight_buffer_write(const char *buf, unsigned count)
+{
+ unsigned ate = 0;
+ while (bfin_read_DBGSTAT() & EMUDOF)
+ continue;
+ bfin_write_emudat(count);
+ while (ate < count) {
+ while (bfin_read_DBGSTAT() & EMUDOF)
+ continue;
+ bfin_write_emudat_chars(buf[ate], buf[ate+1], buf[ate+2], buf[ate+3]);
+ ate += 4;
+ }
+}
+#endif
+
+#ifdef CONFIG_BFIN_JTAG_COMM_CONSOLE
+static void
+bfin_jc_console_write(struct console *co, const char *buf, unsigned count)
+{
+ if (bfin_jc_kthread == NULL)
+ bfin_jc_straight_buffer_write(buf, count);
+ else
+ bfin_jc_circ_write(buf, count);
+}
+
+static struct tty_driver *
+bfin_jc_console_device(struct console *co, int *index)
+{
+ *index = co->index;
+ return bfin_jc_driver;
+}
+
+static struct console bfin_jc_console = {
+ .name = DEV_NAME,
+ .write = bfin_jc_console_write,
+ .device = bfin_jc_console_device,
+ .flags = CON_ANYTIME | CON_PRINTBUFFER,
+ .index = -1,
+};
+
+static int __init bfin_jc_console_init(void)
+{
+ register_console(&bfin_jc_console);
+ return 0;
+}
+console_initcall(bfin_jc_console_init);
+#endif
+
+#ifdef CONFIG_EARLY_PRINTK
+static void __init
+bfin_jc_early_write(struct console *co, const char *buf, unsigned int count)
+{
+ bfin_jc_straight_buffer_write(buf, count);
+}
+
+static struct __initdata console bfin_jc_early_console = {
+ .name = "early_BFJC",
+ .write = bfin_jc_early_write,
+ .flags = CON_ANYTIME | CON_PRINTBUFFER,
+ .index = -1,
+};
+
+struct console * __init
+bfin_jc_early_init(unsigned int port, unsigned int cflag)
+{
+ return &bfin_jc_early_console;
+}
+#endif
+
+MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
+MODULE_DESCRIPTION("TTY over Blackfin JTAG Communication");
+MODULE_LICENSE("GPL");