drivers/char/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 <asm/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_struct * volatile bfin_jc_tty;
  66 static unsigned long bfin_jc_count;
  67 static DEFINE_MUTEX(bfin_jc_tty_mutex);
  68 static volatile struct circ_buf bfin_jc_write_buf;
  69
  70 static int
  71 bfin_jc_emudat_manager(void *arg)
  72 {
  73         uint32_t inbound_len = 0, outbound_len = 0;
  74
  75         while (!kthread_should_stop()) {
  76                 /* no one left to give data to, so sleep */
  77                 if (bfin_jc_tty == NULL && circ_empty(&bfin_jc_write_buf)) {
  78                         pr_debug("waiting for readers\n");
  79                         __set_current_state(TASK_UNINTERRUPTIBLE);
  80                         schedule();
  81                         __set_current_state(TASK_RUNNING);
  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                         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                         struct tty_struct *tty;
  98                         mutex_lock(&bfin_jc_tty_mutex);
  99                         tty = (struct tty_struct *)bfin_jc_tty;
 100                         if (tty != NULL) {
 101                                 uint32_t emudat = bfin_read_emudat();
 102                                 if (inbound_len == 0) {
 103                                         pr_debug("incoming length: 0x%08x\n", emudat);
 104                                         inbound_len = emudat;
 105                                 } else {
 106                                         size_t num_chars = (4 <= inbound_len ? 4 : inbound_len);
 107                                         pr_debug("  incoming data: 0x%08x (pushing %zu)\n", emudat, num_chars);
 108                                         inbound_len -= num_chars;
 109                                         tty_insert_flip_string(tty, (unsigned char *)&emudat, num_chars);
 110                                         tty_flip_buffer_push(tty);
 111                                 }
 112                         }
 113                         mutex_unlock(&bfin_jc_tty_mutex);
 114                 }
 115
 116                 /* if outgoing data is ready, post it */
 117                 if (!(bfin_read_DBGSTAT() & EMUDOF) && !circ_empty(&bfin_jc_write_buf)) {
 118                         if (outbound_len == 0) {
 119                                 outbound_len = circ_cnt(&bfin_jc_write_buf);
 120                                 bfin_write_emudat(outbound_len);
 121                                 pr_debug("outgoing length: 0x%08x\n", outbound_len);
 122                         } else {
 123                                 struct tty_struct *tty;
 124                                 int tail = bfin_jc_write_buf.tail;
 125                                 size_t ate = (4 <= outbound_len ? 4 : outbound_len);
 126                                 uint32_t emudat =
 127                                 bfin_write_emudat_chars(
 128                                         circ_byte(&bfin_jc_write_buf, tail + 0),
 129                                         circ_byte(&bfin_jc_write_buf, tail + 1),
 130                                         circ_byte(&bfin_jc_write_buf, tail + 2),
 131                                         circ_byte(&bfin_jc_write_buf, tail + 3)
 132                                 );
 133                                 bfin_jc_write_buf.tail += ate;
 134                                 outbound_len -= ate;
 135                                 mutex_lock(&bfin_jc_tty_mutex);
 136                                 tty = (struct tty_struct *)bfin_jc_tty;
 137                                 if (tty)
 138                                         tty_wakeup(tty);
 139                                 mutex_unlock(&bfin_jc_tty_mutex);
 140                                 pr_debug("  outgoing data: 0x%08x (pushing %zu)\n", emudat, ate);
 141                         }
 142                 }
 143         }
 144
 145         __set_current_state(TASK_RUNNING);
 146         return 0;
 147 }
 148
 149 static int
 150 bfin_jc_open(struct tty_struct *tty, struct file *filp)
 151 {
 152         mutex_lock(&bfin_jc_tty_mutex);
 153         pr_debug("open %lu\n", bfin_jc_count);
 154         ++bfin_jc_count;
 155         bfin_jc_tty = tty;
 156         wake_up_process(bfin_jc_kthread);
 157         mutex_unlock(&bfin_jc_tty_mutex);
 158         return 0;
 159 }
 160
 161 static void
 162 bfin_jc_close(struct tty_struct *tty, struct file *filp)
 163 {
 164         mutex_lock(&bfin_jc_tty_mutex);
 165         pr_debug("close %lu\n", bfin_jc_count);
 166         if (--bfin_jc_count == 0)
 167                 bfin_jc_tty = NULL;
 168         wake_up_process(bfin_jc_kthread);
 169         mutex_unlock(&bfin_jc_tty_mutex);
 170 }
 171
 172 /* XXX: we dont handle the put_char() case where we must handle count = 1 */
 173 static int
 174 bfin_jc_circ_write(const unsigned char *buf, int count)
 175 {
 176         int i;
 177         count = min(count, circ_free(&bfin_jc_write_buf));
 178         pr_debug("going to write chunk of %i bytes\n", count);
 179         for (i = 0; i < count; ++i)
 180                 circ_byte(&bfin_jc_write_buf, bfin_jc_write_buf.head + i) = buf[i];
 181         bfin_jc_write_buf.head += i;
 182         return i;
 183 }
 184
 185 #ifndef CONFIG_BFIN_JTAG_COMM_CONSOLE
 186 # define acquire_console_sem()
 187 # define release_console_sem()
 188 #endif
 189 static int
 190 bfin_jc_write(struct tty_struct *tty, const unsigned char *buf, int count)
 191 {
 192         int i;
 193         acquire_console_sem();
 194         i = bfin_jc_circ_write(buf, count);
 195         release_console_sem();
 196         wake_up_process(bfin_jc_kthread);
 197         return i;
 198 }
 199
 200 static void
 201 bfin_jc_flush_chars(struct tty_struct *tty)
 202 {
 203         wake_up_process(bfin_jc_kthread);
 204 }
 205
 206 static int
 207 bfin_jc_write_room(struct tty_struct *tty)
 208 {
 209         return circ_free(&bfin_jc_write_buf);
 210 }
 211
 212 static int
 213 bfin_jc_chars_in_buffer(struct tty_struct *tty)
 214 {
 215         return circ_cnt(&bfin_jc_write_buf);
 216 }
 217
 218 static void
 219 bfin_jc_wait_until_sent(struct tty_struct *tty, int timeout)
 220 {
 221         unsigned long expire = jiffies + timeout;
 222         while (!circ_empty(&bfin_jc_write_buf)) {
 223                 if (signal_pending(current))
 224                         break;
 225                 if (time_after(jiffies, expire))
 226                         break;
 227         }
 228 }
 229
 230 static const struct tty_operations bfin_jc_ops = {
 231         .open            = bfin_jc_open,
 232         .close           = bfin_jc_close,
 233         .write           = bfin_jc_write,
 234         /*.put_char        = bfin_jc_put_char,*/
 235         .flush_chars     = bfin_jc_flush_chars,
 236         .write_room      = bfin_jc_write_room,
 237         .chars_in_buffer = bfin_jc_chars_in_buffer,
 238         .wait_until_sent = bfin_jc_wait_until_sent,
 239 };
 240
 241 static int __init bfin_jc_init(void)
 242 {
 243         int ret;
 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;
 255
 256         bfin_jc_driver = alloc_tty_driver(1);
 257         if (!bfin_jc_driver)
 258                 goto err;
 259
 260         bfin_jc_driver->owner        = THIS_MODULE;
 261         bfin_jc_driver->driver_name  = DRV_NAME;
 262         bfin_jc_driver->name         = DEV_NAME;
 263         bfin_jc_driver->type         = TTY_DRIVER_TYPE_SERIAL;
 264         bfin_jc_driver->subtype      = SERIAL_TYPE_NORMAL;
 265         bfin_jc_driver->init_termios = tty_std_termios;
 266         tty_set_operations(bfin_jc_driver, &bfin_jc_ops);
 267
 268         ret = tty_register_driver(bfin_jc_driver);
 269         if (ret)
 270                 goto err;
 271
 272         pr_init(KERN_INFO DRV_NAME ": initialized\n");
 273
 274         return 0;
 275
 276  err:
 277         put_tty_driver(bfin_jc_driver);
 278         kfree(bfin_jc_write_buf.buf);
 279         kthread_stop(bfin_jc_kthread);
 280         return ret;
 281 }
 282 module_init(bfin_jc_init);
 283
 284 static void __exit bfin_jc_exit(void)
 285 {
 286         kthread_stop(bfin_jc_kthread);
 287         kfree(bfin_jc_write_buf.buf);
 288         tty_unregister_driver(bfin_jc_driver);
 289         put_tty_driver(bfin_jc_driver);
 290 }
 291 module_exit(bfin_jc_exit);
 292
 293 #if defined(CONFIG_BFIN_JTAG_COMM_CONSOLE) || defined(CONFIG_EARLY_PRINTK)
 294 static void
 295 bfin_jc_straight_buffer_write(const char *buf, unsigned count)
 296 {
 297         unsigned ate = 0;
 298         while (bfin_read_DBGSTAT() & EMUDOF)
 299                 continue;
 300         bfin_write_emudat(count);
 301         while (ate < count) {
 302                 while (bfin_read_DBGSTAT() & EMUDOF)
 303                         continue;
 304                 bfin_write_emudat_chars(buf[ate], buf[ate+1], buf[ate+2], buf[ate+3]);
 305                 ate += 4;
 306         }
 307 }
 308 #endif
 309
 310 #ifdef CONFIG_BFIN_JTAG_COMM_CONSOLE
 311 static void
 312 bfin_jc_console_write(struct console *co, const char *buf, unsigned count)
 313 {
 314         if (bfin_jc_kthread == NULL)
 315                 bfin_jc_straight_buffer_write(buf, count);
 316         else
 317                 bfin_jc_circ_write(buf, count);
 318 }
 319
 320 static struct tty_driver *
 321 bfin_jc_console_device(struct console *co, int *index)
 322 {
 323         *index = co->index;
 324         return bfin_jc_driver;
 325 }
 326
 327 static struct console bfin_jc_console = {
 328         .name    = DEV_NAME,
 329         .write   = bfin_jc_console_write,
 330         .device  = bfin_jc_console_device,
 331         .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 332         .index   = -1,
 333 };
 334
 335 static int __init bfin_jc_console_init(void)
 336 {
 337         register_console(&bfin_jc_console);
 338         return 0;
 339 }
 340 console_initcall(bfin_jc_console_init);
 341 #endif
 342
 343 #ifdef CONFIG_EARLY_PRINTK
 344 static void __init
 345 bfin_jc_early_write(struct console *co, const char *buf, unsigned int count)
 346 {
 347         bfin_jc_straight_buffer_write(buf, count);
 348 }
 349
 350 static struct __initdata console bfin_jc_early_console = {
 351         .name   = "early_BFJC",
 352         .write   = bfin_jc_early_write,
 353         .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 354         .index   = -1,
 355 };
 356
 357 struct console * __init
 358 bfin_jc_early_init(unsigned int port, unsigned int cflag)
 359 {
 360         return &bfin_jc_early_console;
 361 }
 362 #endif
 363
 364 MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
 365 MODULE_DESCRIPTION("TTY over Blackfin JTAG Communication");
 366 MODULE_LICENSE("GPL");