drivers/tty/bfin_jtag_comm.c

   1 /*
   2  * TTY over Blackfin JTAG Communication
   3  *
   4  * Copyright 2008-2009 Analog Devices Inc.
   5  *
   6  * Enter bugs at http://blackfin.uclinux.org/
   7  *
   8  * Licensed under the GPL-2 or later.
   9  */
  10
  11 #define DRV_NAME "bfin-jtag-comm"
  12 #define DEV_NAME "ttyBFJC"
  13 #define pr_fmt(fmt) DRV_NAME ": " fmt
  14
  15 #include <linux/circ_buf.h>
  16 #include <linux/console.h>
  17 #include <linux/delay.h>
  18 #include <linux/err.h>
  19 #include <linux/kernel.h>
  20 #include <linux/kthread.h>
  21 #include <linux/module.h>
  22 #include <linux/mutex.h>
  23 #include <linux/sched.h>
  24 #include <linux/slab.h>
  25 #include <linux/tty.h>
  26 #include <linux/tty_driver.h>
  27 #include <linux/tty_flip.h>
  28 #include <linux/atomic.h>
  29
  30 #define pr_init(fmt, args...) ({ static const __initconst char __fmt[] = fmt; printk(__fmt, ## args); })
  31
  32 /* See the Debug/Emulation chapter in the HRM */
  33 #define EMUDOF   0x00000001     /* EMUDAT_OUT full & valid */
  34 #define EMUDIF   0x00000002     /* EMUDAT_IN full & valid */
  35 #define EMUDOOVF 0x00000004     /* EMUDAT_OUT overflow */
  36 #define EMUDIOVF 0x00000008     /* EMUDAT_IN overflow */
  37
  38 static inline uint32_t bfin_write_emudat(uint32_t emudat)
  39 {
  40         __asm__ __volatile__("emudat = %0;" : : "d"(emudat));
  41         return emudat;
  42 }
  43
  44 static inline uint32_t bfin_read_emudat(void)
  45 {
  46         uint32_t emudat;
  47         __asm__ __volatile__("%0 = emudat;" : "=d"(emudat));
  48         return emudat;
  49 }
  50
  51 static inline uint32_t bfin_write_emudat_chars(char a, char b, char c, char d)
  52 {
  53         return bfin_write_emudat((a << 0) | (b << 8) | (c << 16) | (d << 24));
  54 }
  55
  56 #define CIRC_SIZE 2048  /* see comment in tty_io.c:do_tty_write() */
  57 #define CIRC_MASK (CIRC_SIZE - 1)
  58 #define circ_empty(circ)     ((circ)->head == (circ)->tail)
  59 #define circ_free(circ)      CIRC_SPACE((circ)->head, (circ)->tail, CIRC_SIZE)
  60 #define circ_cnt(circ)       CIRC_CNT((circ)->head, (circ)->tail, CIRC_SIZE)
  61 #define circ_byte(circ, idx) ((circ)->buf[(idx) & CIRC_MASK])
  62
  63 static struct tty_driver *bfin_jc_driver;
  64 static struct task_struct *bfin_jc_kthread;
  65 static struct tty_port port;
  66 static volatile struct circ_buf bfin_jc_write_buf;
  67
  68 static int
  69 bfin_jc_emudat_manager(void *arg)
  70 {
  71         uint32_t inbound_len = 0, outbound_len = 0;
  72
  73         while (!kthread_should_stop()) {
  74                 struct tty_struct *tty = tty_port_tty_get(&port);
  75                 /* no one left to give data to, so sleep */
  76                 if (tty == NULL && circ_empty(&bfin_jc_write_buf)) {
  77                         pr_debug("waiting for readers\n");
  78                         __set_current_state(TASK_UNINTERRUPTIBLE);
  79                         schedule();
  80                         continue;
  81                 }
  82
  83                 /* no data available, so just chill */
  84                 if (!(bfin_read_DBGSTAT() & EMUDIF) && circ_empty(&bfin_jc_write_buf)) {
  85                         pr_debug("waiting for data (in_len = %i) (circ: %i %i)\n",
  86                                 inbound_len, bfin_jc_write_buf.tail, bfin_jc_write_buf.head);
  87                         tty_kref_put(tty);
  88                         if (inbound_len)
  89                                 schedule();
  90                         else
  91                                 schedule_timeout_interruptible(HZ);
  92                         continue;
  93                 }
  94
  95                 /* if incoming data is ready, eat it */
  96                 if (bfin_read_DBGSTAT() & EMUDIF) {
  97                         uint32_t emudat = bfin_read_emudat();
  98                         if (inbound_len == 0) {
  99                                 pr_debug("incoming length: 0x%08x\n", emudat);
 100                                 inbound_len = emudat;
 101                         } else {
 102                                 size_t num_chars = (4 <= inbound_len ? 4 : inbound_len);
 103                                 pr_debug("  incoming data: 0x%08x (pushing %zu)\n", emudat, num_chars);
 104                                 inbound_len -= num_chars;
 105                                 tty_insert_flip_string(&port, (unsigned char *)&emudat, num_chars);
 106                                 tty_flip_buffer_push(&port);
 107                         }
 108                 }
 109
 110                 /* if outgoing data is ready, post it */
 111                 if (!(bfin_read_DBGSTAT() & EMUDOF) && !circ_empty(&bfin_jc_write_buf)) {
 112                         if (outbound_len == 0) {
 113                                 outbound_len = circ_cnt(&bfin_jc_write_buf);
 114                                 bfin_write_emudat(outbound_len);
 115                                 pr_debug("outgoing length: 0x%08x\n", outbound_len);
 116                         } else {
 117                                 int tail = bfin_jc_write_buf.tail;
 118                                 size_t ate = (4 <= outbound_len ? 4 : outbound_len);
 119                                 uint32_t emudat =
 120                                 bfin_write_emudat_chars(
 121                                         circ_byte(&bfin_jc_write_buf, tail + 0),
 122                                         circ_byte(&bfin_jc_write_buf, tail + 1),
 123                                         circ_byte(&bfin_jc_write_buf, tail + 2),
 124                                         circ_byte(&bfin_jc_write_buf, tail + 3)
 125                                 );
 126                                 bfin_jc_write_buf.tail += ate;
 127                                 outbound_len -= ate;
 128                                 if (tty)
 129                                         tty_wakeup(tty);
 130                                 pr_debug("  outgoing data: 0x%08x (pushing %zu)\n", emudat, ate);
 131                         }
 132                 }
 133                 tty_kref_put(tty);
 134         }
 135
 136         __set_current_state(TASK_RUNNING);
 137         return 0;
 138 }
 139
 140 static int
 141 bfin_jc_open(struct tty_struct *tty, struct file *filp)
 142 {
 143         unsigned long flags;
 144
 145         spin_lock_irqsave(&port.lock, flags);
 146         port.count++;
 147         spin_unlock_irqrestore(&port.lock, flags);
 148         tty_port_tty_set(&port, tty);
 149         wake_up_process(bfin_jc_kthread);
 150         return 0;
 151 }
 152
 153 static void
 154 bfin_jc_close(struct tty_struct *tty, struct file *filp)
 155 {
 156         unsigned long flags;
 157         bool last;
 158
 159         spin_lock_irqsave(&port.lock, flags);
 160         last = --port.count == 0;
 161         spin_unlock_irqrestore(&port.lock, flags);
 162         if (last)
 163                 tty_port_tty_set(&port, NULL);
 164         wake_up_process(bfin_jc_kthread);
 165 }
 166
 167 /* XXX: we dont handle the put_char() case where we must handle count = 1 */
 168 static int
 169 bfin_jc_circ_write(const unsigned char *buf, int count)
 170 {
 171         int i;
 172         count = min(count, circ_free(&bfin_jc_write_buf));
 173         pr_debug("going to write chunk of %i bytes\n", count);
 174         for (i = 0; i < count; ++i)
 175                 circ_byte(&bfin_jc_write_buf, bfin_jc_write_buf.head + i) = buf[i];
 176         bfin_jc_write_buf.head += i;
 177         return i;
 178 }
 179
 180 #ifndef CONFIG_BFIN_JTAG_COMM_CONSOLE
 181 # define console_lock()
 182 # define console_unlock()
 183 #endif
 184 static int
 185 bfin_jc_write(struct tty_struct *tty, const unsigned char *buf, int count)
 186 {
 187         int i;
 188         console_lock();
 189         i = bfin_jc_circ_write(buf, count);
 190         console_unlock();
 191         wake_up_process(bfin_jc_kthread);
 192         return i;
 193 }
 194
 195 static void
 196 bfin_jc_flush_chars(struct tty_struct *tty)
 197 {
 198         wake_up_process(bfin_jc_kthread);
 199 }
 200
 201 static int
 202 bfin_jc_write_room(struct tty_struct *tty)
 203 {
 204         return circ_free(&bfin_jc_write_buf);
 205 }
 206
 207 static int
 208 bfin_jc_chars_in_buffer(struct tty_struct *tty)
 209 {
 210         return circ_cnt(&bfin_jc_write_buf);
 211 }
 212
 213 static const struct tty_operations bfin_jc_ops = {
 214         .open            = bfin_jc_open,
 215         .close           = bfin_jc_close,
 216         .write           = bfin_jc_write,
 217         /*.put_char        = bfin_jc_put_char,*/
 218         .flush_chars     = bfin_jc_flush_chars,
 219         .write_room      = bfin_jc_write_room,
 220         .chars_in_buffer = bfin_jc_chars_in_buffer,
 221 };
 222
 223 static int __init bfin_jc_init(void)
 224 {
 225         int ret;
 226
 227         bfin_jc_kthread = kthread_create(bfin_jc_emudat_manager, NULL, DRV_NAME);
 228         if (IS_ERR(bfin_jc_kthread))
 229                 return PTR_ERR(bfin_jc_kthread);
 230
 231         ret = -ENOMEM;
 232
 233         bfin_jc_write_buf.head = bfin_jc_write_buf.tail = 0;
 234         bfin_jc_write_buf.buf = kmalloc(CIRC_SIZE, GFP_KERNEL);
 235         if (!bfin_jc_write_buf.buf)
 236                 goto err_buf;
 237
 238         bfin_jc_driver = alloc_tty_driver(1);
 239         if (!bfin_jc_driver)
 240                 goto err_driver;
 241
 242         tty_port_init(&port);
 243
 244         bfin_jc_driver->driver_name  = DRV_NAME;
 245         bfin_jc_driver->name         = DEV_NAME;
 246         bfin_jc_driver->type         = TTY_DRIVER_TYPE_SERIAL;
 247         bfin_jc_driver->subtype      = SERIAL_TYPE_NORMAL;
 248         bfin_jc_driver->init_termios = tty_std_termios;
 249         tty_set_operations(bfin_jc_driver, &bfin_jc_ops);
 250         tty_port_link_device(&port, bfin_jc_driver, 0);
 251
 252         ret = tty_register_driver(bfin_jc_driver);
 253         if (ret)
 254                 goto err;
 255
 256         pr_init(KERN_INFO DRV_NAME ": initialized\n");
 257
 258         return 0;
 259
 260  err:
 261         tty_port_destroy(&port);
 262         put_tty_driver(bfin_jc_driver);
 263  err_driver:
 264         kfree(bfin_jc_write_buf.buf);
 265  err_buf:
 266         kthread_stop(bfin_jc_kthread);
 267         return ret;
 268 }
 269 module_init(bfin_jc_init);
 270
 271 static void __exit bfin_jc_exit(void)
 272 {
 273         kthread_stop(bfin_jc_kthread);
 274         kfree(bfin_jc_write_buf.buf);
 275         tty_unregister_driver(bfin_jc_driver);
 276         put_tty_driver(bfin_jc_driver);
 277         tty_port_destroy(&port);
 278 }
 279 module_exit(bfin_jc_exit);
 280
 281 #if defined(CONFIG_BFIN_JTAG_COMM_CONSOLE) || defined(CONFIG_EARLY_PRINTK)
 282 static void
 283 bfin_jc_straight_buffer_write(const char *buf, unsigned count)
 284 {
 285         unsigned ate = 0;
 286         while (bfin_read_DBGSTAT() & EMUDOF)
 287                 continue;
 288         bfin_write_emudat(count);
 289         while (ate < count) {
 290                 while (bfin_read_DBGSTAT() & EMUDOF)
 291                         continue;
 292                 bfin_write_emudat_chars(buf[ate], buf[ate+1], buf[ate+2], buf[ate+3]);
 293                 ate += 4;
 294         }
 295 }
 296 #endif
 297
 298 #ifdef CONFIG_BFIN_JTAG_COMM_CONSOLE
 299 static void
 300 bfin_jc_console_write(struct console *co, const char *buf, unsigned count)
 301 {
 302         if (bfin_jc_kthread == NULL)
 303                 bfin_jc_straight_buffer_write(buf, count);
 304         else
 305                 bfin_jc_circ_write(buf, count);
 306 }
 307
 308 static struct tty_driver *
 309 bfin_jc_console_device(struct console *co, int *index)
 310 {
 311         *index = co->index;
 312         return bfin_jc_driver;
 313 }
 314
 315 static struct console bfin_jc_console = {
 316         .name    = DEV_NAME,
 317         .write   = bfin_jc_console_write,
 318         .device  = bfin_jc_console_device,
 319         .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 320         .index   = -1,
 321 };
 322
 323 static int __init bfin_jc_console_init(void)
 324 {
 325         register_console(&bfin_jc_console);
 326         return 0;
 327 }
 328 console_initcall(bfin_jc_console_init);
 329 #endif
 330
 331 #ifdef CONFIG_EARLY_PRINTK
 332 static void __init
 333 bfin_jc_early_write(struct console *co, const char *buf, unsigned int count)
 334 {
 335         bfin_jc_straight_buffer_write(buf, count);
 336 }
 337
 338 static struct console bfin_jc_early_console __initdata = {
 339         .name   = "early_BFJC",
 340         .write   = bfin_jc_early_write,
 341         .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 342         .index   = -1,
 343 };
 344
 345 struct console * __init
 346 bfin_jc_early_init(unsigned int port, unsigned int cflag)
 347 {
 348         return &bfin_jc_early_console;
 349 }
 350 #endif
 351
 352 MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
 353 MODULE_DESCRIPTION("TTY over Blackfin JTAG Communication");
 354 MODULE_LICENSE("GPL");