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                         __set_current_state(TASK_RUNNING);
  81                         continue;
  82                 }
  83
  84                 /* no data available, so just chill */
  85                 if (!(bfin_read_DBGSTAT() & EMUDIF) && circ_empty(&bfin_jc_write_buf)) {
  86                         pr_debug("waiting for data (in_len = %i) (circ: %i %i)\n",
  87                                 inbound_len, bfin_jc_write_buf.tail, bfin_jc_write_buf.head);
  88                         tty_kref_put(tty);
  89                         if (inbound_len)
  90                                 schedule();
  91                         else
  92                                 schedule_timeout_interruptible(HZ);
  93                         continue;
  94                 }
  95
  96                 /* if incoming data is ready, eat it */
  97                 if (bfin_read_DBGSTAT() & EMUDIF) {
  98                         if (tty != NULL) {
  99                                 uint32_t emudat = bfin_read_emudat();
 100                                 if (inbound_len == 0) {
 101                                         pr_debug("incoming length: 0x%08x\n", emudat);
 102                                         inbound_len = emudat;
 103                                 } else {
 104                                         size_t num_chars = (4 <= inbound_len ? 4 : inbound_len);
 105                                         pr_debug("  incoming data: 0x%08x (pushing %zu)\n", emudat, num_chars);
 106                                         inbound_len -= num_chars;
 107                                         tty_insert_flip_string(tty, (unsigned char *)&emudat, num_chars);
 108                                         tty_flip_buffer_push(tty);
 109                                 }
 110                         }
 111                 }
 112
 113                 /* if outgoing data is ready, post it */
 114                 if (!(bfin_read_DBGSTAT() & EMUDOF) && !circ_empty(&bfin_jc_write_buf)) {
 115                         if (outbound_len == 0) {
 116                                 outbound_len = circ_cnt(&bfin_jc_write_buf);
 117                                 bfin_write_emudat(outbound_len);
 118                                 pr_debug("outgoing length: 0x%08x\n", outbound_len);
 119                         } else {
 120                                 int tail = bfin_jc_write_buf.tail;
 121                                 size_t ate = (4 <= outbound_len ? 4 : outbound_len);
 122                                 uint32_t emudat =
 123                                 bfin_write_emudat_chars(
 124                                         circ_byte(&bfin_jc_write_buf, tail + 0),
 125                                         circ_byte(&bfin_jc_write_buf, tail + 1),
 126                                         circ_byte(&bfin_jc_write_buf, tail + 2),
 127                                         circ_byte(&bfin_jc_write_buf, tail + 3)
 128                                 );
 129                                 bfin_jc_write_buf.tail += ate;
 130                                 outbound_len -= ate;
 131                                 if (tty)
 132                                         tty_wakeup(tty);
 133                                 pr_debug("  outgoing data: 0x%08x (pushing %zu)\n", emudat, ate);
 134                         }
 135                 }
 136                 tty_kref_put(tty);
 137         }
 138
 139         __set_current_state(TASK_RUNNING);
 140         return 0;
 141 }
 142
 143 static int
 144 bfin_jc_open(struct tty_struct *tty, struct file *filp)
 145 {
 146         unsigned long flags;
 147
 148         spin_lock_irqsave(&port.lock, flags);
 149         port.count++;
 150         spin_unlock_irqrestore(&port.lock, flags);
 151         tty_port_tty_set(&port, tty);
 152         wake_up_process(bfin_jc_kthread);
 153         return 0;
 154 }
 155
 156 static void
 157 bfin_jc_close(struct tty_struct *tty, struct file *filp)
 158 {
 159         unsigned long flags;
 160         bool last;
 161
 162         spin_lock_irqsave(&port.lock, flags);
 163         last = --port.count == 0;
 164         spin_unlock_irqrestore(&port.lock, flags);
 165         if (last)
 166                 tty_port_tty_set(&port, NULL);
 167         wake_up_process(bfin_jc_kthread);
 168 }
 169
 170 /* XXX: we dont handle the put_char() case where we must handle count = 1 */
 171 static int
 172 bfin_jc_circ_write(const unsigned char *buf, int count)
 173 {
 174         int i;
 175         count = min(count, circ_free(&bfin_jc_write_buf));
 176         pr_debug("going to write chunk of %i bytes\n", count);
 177         for (i = 0; i < count; ++i)
 178                 circ_byte(&bfin_jc_write_buf, bfin_jc_write_buf.head + i) = buf[i];
 179         bfin_jc_write_buf.head += i;
 180         return i;
 181 }
 182
 183 #ifndef CONFIG_BFIN_JTAG_COMM_CONSOLE
 184 # define console_lock()
 185 # define console_unlock()
 186 #endif
 187 static int
 188 bfin_jc_write(struct tty_struct *tty, const unsigned char *buf, int count)
 189 {
 190         int i;
 191         console_lock();
 192         i = bfin_jc_circ_write(buf, count);
 193         console_unlock();
 194         wake_up_process(bfin_jc_kthread);
 195         return i;
 196 }
 197
 198 static void
 199 bfin_jc_flush_chars(struct tty_struct *tty)
 200 {
 201         wake_up_process(bfin_jc_kthread);
 202 }
 203
 204 static int
 205 bfin_jc_write_room(struct tty_struct *tty)
 206 {
 207         return circ_free(&bfin_jc_write_buf);
 208 }
 209
 210 static int
 211 bfin_jc_chars_in_buffer(struct tty_struct *tty)
 212 {
 213         return circ_cnt(&bfin_jc_write_buf);
 214 }
 215
 216 static void
 217 bfin_jc_wait_until_sent(struct tty_struct *tty, int timeout)
 218 {
 219         unsigned long expire = jiffies + timeout;
 220         while (!circ_empty(&bfin_jc_write_buf)) {
 221                 if (signal_pending(current))
 222                         break;
 223                 if (time_after(jiffies, expire))
 224                         break;
 225         }
 226 }
 227
 228 static const struct tty_operations bfin_jc_ops = {
 229         .open            = bfin_jc_open,
 230         .close           = bfin_jc_close,
 231         .write           = bfin_jc_write,
 232         /*.put_char        = bfin_jc_put_char,*/
 233         .flush_chars     = bfin_jc_flush_chars,
 234         .write_room      = bfin_jc_write_room,
 235         .chars_in_buffer = bfin_jc_chars_in_buffer,
 236         .wait_until_sent = bfin_jc_wait_until_sent,
 237 };
 238
 239 static int __init bfin_jc_init(void)
 240 {
 241         int ret;
 242
 243         tty_port_init(&port);
 244
 245         bfin_jc_kthread = kthread_create(bfin_jc_emudat_manager, NULL, DRV_NAME);
 246         if (IS_ERR(bfin_jc_kthread))
 247                 return PTR_ERR(bfin_jc_kthread);
 248
 249         ret = -ENOMEM;
 250
 251         bfin_jc_write_buf.head = bfin_jc_write_buf.tail = 0;
 252         bfin_jc_write_buf.buf = kmalloc(CIRC_SIZE, GFP_KERNEL);
 253         if (!bfin_jc_write_buf.buf)
 254                 goto err_buf;
 255
 256         bfin_jc_driver = alloc_tty_driver(1);
 257         if (!bfin_jc_driver)
 258                 goto err_driver;
 259
 260         bfin_jc_driver->driver_name  = DRV_NAME;
 261         bfin_jc_driver->name         = DEV_NAME;
 262         bfin_jc_driver->type         = TTY_DRIVER_TYPE_SERIAL;
 263         bfin_jc_driver->subtype      = SERIAL_TYPE_NORMAL;
 264         bfin_jc_driver->init_termios = tty_std_termios;
 265         tty_set_operations(bfin_jc_driver, &bfin_jc_ops);
 266
 267         ret = tty_register_driver(bfin_jc_driver);
 268         if (ret)
 269                 goto err;
 270
 271         pr_init(KERN_INFO DRV_NAME ": initialized\n");
 272
 273         return 0;
 274
 275  err:
 276         put_tty_driver(bfin_jc_driver);
 277  err_driver:
 278         kfree(bfin_jc_write_buf.buf);
 279  err_buf:
 280         kthread_stop(bfin_jc_kthread);
 281         return ret;
 282 }
 283 module_init(bfin_jc_init);
 284
 285 static void __exit bfin_jc_exit(void)
 286 {
 287         kthread_stop(bfin_jc_kthread);
 288         kfree(bfin_jc_write_buf.buf);
 289         tty_unregister_driver(bfin_jc_driver);
 290         put_tty_driver(bfin_jc_driver);
 291 }
 292 module_exit(bfin_jc_exit);
 293
 294 #if defined(CONFIG_BFIN_JTAG_COMM_CONSOLE) || defined(CONFIG_EARLY_PRINTK)
 295 static void
 296 bfin_jc_straight_buffer_write(const char *buf, unsigned count)
 297 {
 298         unsigned ate = 0;
 299         while (bfin_read_DBGSTAT() & EMUDOF)
 300                 continue;
 301         bfin_write_emudat(count);
 302         while (ate < count) {
 303                 while (bfin_read_DBGSTAT() & EMUDOF)
 304                         continue;
 305                 bfin_write_emudat_chars(buf[ate], buf[ate+1], buf[ate+2], buf[ate+3]);
 306                 ate += 4;
 307         }
 308 }
 309 #endif
 310
 311 #ifdef CONFIG_BFIN_JTAG_COMM_CONSOLE
 312 static void
 313 bfin_jc_console_write(struct console *co, const char *buf, unsigned count)
 314 {
 315         if (bfin_jc_kthread == NULL)
 316                 bfin_jc_straight_buffer_write(buf, count);
 317         else
 318                 bfin_jc_circ_write(buf, count);
 319 }
 320
 321 static struct tty_driver *
 322 bfin_jc_console_device(struct console *co, int *index)
 323 {
 324         *index = co->index;
 325         return bfin_jc_driver;
 326 }
 327
 328 static struct console bfin_jc_console = {
 329         .name    = DEV_NAME,
 330         .write   = bfin_jc_console_write,
 331         .device  = bfin_jc_console_device,
 332         .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 333         .index   = -1,
 334 };
 335
 336 static int __init bfin_jc_console_init(void)
 337 {
 338         register_console(&bfin_jc_console);
 339         return 0;
 340 }
 341 console_initcall(bfin_jc_console_init);
 342 #endif
 343
 344 #ifdef CONFIG_EARLY_PRINTK
 345 static void __init
 346 bfin_jc_early_write(struct console *co, const char *buf, unsigned int count)
 347 {
 348         bfin_jc_straight_buffer_write(buf, count);
 349 }
 350
 351 static struct __initdata console bfin_jc_early_console = {
 352         .name   = "early_BFJC",
 353         .write   = bfin_jc_early_write,
 354         .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 355         .index   = -1,
 356 };
 357
 358 struct console * __init
 359 bfin_jc_early_init(unsigned int port, unsigned int cflag)
 360 {
 361         return &bfin_jc_early_console;
 362 }
 363 #endif
 364
 365 MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
 366 MODULE_DESCRIPTION("TTY over Blackfin JTAG Communication");
 367 MODULE_LICENSE("GPL");