linux/drivers/tty/bfin_jtag_comm.c
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   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
  38static inline uint32_t bfin_write_emudat(uint32_t emudat)
  39{
  40        __asm__ __volatile__("emudat = %0;" : : "d"(emudat));
  41        return emudat;
  42}
  43
  44static inline uint32_t bfin_read_emudat(void)
  45{
  46        uint32_t emudat;
  47        __asm__ __volatile__("%0 = emudat;" : "=d"(emudat));
  48        return emudat;
  49}
  50
  51static 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
  63static struct tty_driver *bfin_jc_driver;
  64static struct task_struct *bfin_jc_kthread;
  65static struct tty_port port;
  66static volatile struct circ_buf bfin_jc_write_buf;
  67
  68static int
  69bfin_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                        uint32_t emudat = bfin_read_emudat();
  99                        if (inbound_len == 0) {
 100                                pr_debug("incoming length: 0x%08x\n", emudat);
 101                                inbound_len = emudat;
 102                        } else {
 103                                size_t num_chars = (4 <= inbound_len ? 4 : inbound_len);
 104                                pr_debug("  incoming data: 0x%08x (pushing %zu)\n", emudat, num_chars);
 105                                inbound_len -= num_chars;
 106                                tty_insert_flip_string(&port, (unsigned char *)&emudat, num_chars);
 107                                tty_flip_buffer_push(&port);
 108                        }
 109                }
 110
 111                /* if outgoing data is ready, post it */
 112                if (!(bfin_read_DBGSTAT() & EMUDOF) && !circ_empty(&bfin_jc_write_buf)) {
 113                        if (outbound_len == 0) {
 114                                outbound_len = circ_cnt(&bfin_jc_write_buf);
 115                                bfin_write_emudat(outbound_len);
 116                                pr_debug("outgoing length: 0x%08x\n", outbound_len);
 117                        } else {
 118                                int tail = bfin_jc_write_buf.tail;
 119                                size_t ate = (4 <= outbound_len ? 4 : outbound_len);
 120                                uint32_t emudat =
 121                                bfin_write_emudat_chars(
 122                                        circ_byte(&bfin_jc_write_buf, tail + 0),
 123                                        circ_byte(&bfin_jc_write_buf, tail + 1),
 124                                        circ_byte(&bfin_jc_write_buf, tail + 2),
 125                                        circ_byte(&bfin_jc_write_buf, tail + 3)
 126                                );
 127                                bfin_jc_write_buf.tail += ate;
 128                                outbound_len -= ate;
 129                                if (tty)
 130                                        tty_wakeup(tty);
 131                                pr_debug("  outgoing data: 0x%08x (pushing %zu)\n", emudat, ate);
 132                        }
 133                }
 134                tty_kref_put(tty);
 135        }
 136
 137        __set_current_state(TASK_RUNNING);
 138        return 0;
 139}
 140
 141static int
 142bfin_jc_open(struct tty_struct *tty, struct file *filp)
 143{
 144        unsigned long flags;
 145
 146        spin_lock_irqsave(&port.lock, flags);
 147        port.count++;
 148        spin_unlock_irqrestore(&port.lock, flags);
 149        tty_port_tty_set(&port, tty);
 150        wake_up_process(bfin_jc_kthread);
 151        return 0;
 152}
 153
 154static void
 155bfin_jc_close(struct tty_struct *tty, struct file *filp)
 156{
 157        unsigned long flags;
 158        bool last;
 159
 160        spin_lock_irqsave(&port.lock, flags);
 161        last = --port.count == 0;
 162        spin_unlock_irqrestore(&port.lock, flags);
 163        if (last)
 164                tty_port_tty_set(&port, NULL);
 165        wake_up_process(bfin_jc_kthread);
 166}
 167
 168/* XXX: we dont handle the put_char() case where we must handle count = 1 */
 169static int
 170bfin_jc_circ_write(const unsigned char *buf, int count)
 171{
 172        int i;
 173        count = min(count, circ_free(&bfin_jc_write_buf));
 174        pr_debug("going to write chunk of %i bytes\n", count);
 175        for (i = 0; i < count; ++i)
 176                circ_byte(&bfin_jc_write_buf, bfin_jc_write_buf.head + i) = buf[i];
 177        bfin_jc_write_buf.head += i;
 178        return i;
 179}
 180
 181#ifndef CONFIG_BFIN_JTAG_COMM_CONSOLE
 182# define console_lock()
 183# define console_unlock()
 184#endif
 185static int
 186bfin_jc_write(struct tty_struct *tty, const unsigned char *buf, int count)
 187{
 188        int i;
 189        console_lock();
 190        i = bfin_jc_circ_write(buf, count);
 191        console_unlock();
 192        wake_up_process(bfin_jc_kthread);
 193        return i;
 194}
 195
 196static void
 197bfin_jc_flush_chars(struct tty_struct *tty)
 198{
 199        wake_up_process(bfin_jc_kthread);
 200}
 201
 202static int
 203bfin_jc_write_room(struct tty_struct *tty)
 204{
 205        return circ_free(&bfin_jc_write_buf);
 206}
 207
 208static int
 209bfin_jc_chars_in_buffer(struct tty_struct *tty)
 210{
 211        return circ_cnt(&bfin_jc_write_buf);
 212}
 213
 214static void
 215bfin_jc_wait_until_sent(struct tty_struct *tty, int timeout)
 216{
 217        unsigned long expire = jiffies + timeout;
 218        while (!circ_empty(&bfin_jc_write_buf)) {
 219                if (signal_pending(current))
 220                        break;
 221                if (time_after(jiffies, expire))
 222                        break;
 223        }
 224}
 225
 226static const struct tty_operations bfin_jc_ops = {
 227        .open            = bfin_jc_open,
 228        .close           = bfin_jc_close,
 229        .write           = bfin_jc_write,
 230        /*.put_char        = bfin_jc_put_char,*/
 231        .flush_chars     = bfin_jc_flush_chars,
 232        .write_room      = bfin_jc_write_room,
 233        .chars_in_buffer = bfin_jc_chars_in_buffer,
 234        .wait_until_sent = bfin_jc_wait_until_sent,
 235};
 236
 237static int __init bfin_jc_init(void)
 238{
 239        int ret;
 240
 241        bfin_jc_kthread = kthread_create(bfin_jc_emudat_manager, NULL, DRV_NAME);
 242        if (IS_ERR(bfin_jc_kthread))
 243                return PTR_ERR(bfin_jc_kthread);
 244
 245        ret = -ENOMEM;
 246
 247        bfin_jc_write_buf.head = bfin_jc_write_buf.tail = 0;
 248        bfin_jc_write_buf.buf = kmalloc(CIRC_SIZE, GFP_KERNEL);
 249        if (!bfin_jc_write_buf.buf)
 250                goto err_buf;
 251
 252        bfin_jc_driver = alloc_tty_driver(1);
 253        if (!bfin_jc_driver)
 254                goto err_driver;
 255
 256        tty_port_init(&port);
 257
 258        bfin_jc_driver->driver_name  = DRV_NAME;
 259        bfin_jc_driver->name         = DEV_NAME;
 260        bfin_jc_driver->type         = TTY_DRIVER_TYPE_SERIAL;
 261        bfin_jc_driver->subtype      = SERIAL_TYPE_NORMAL;
 262        bfin_jc_driver->init_termios = tty_std_termios;
 263        tty_set_operations(bfin_jc_driver, &bfin_jc_ops);
 264        tty_port_link_device(&port, bfin_jc_driver, 0);
 265
 266        ret = tty_register_driver(bfin_jc_driver);
 267        if (ret)
 268                goto err;
 269
 270        pr_init(KERN_INFO DRV_NAME ": initialized\n");
 271
 272        return 0;
 273
 274 err:
 275        tty_port_destroy(&port);
 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}
 283module_init(bfin_jc_init);
 284
 285static 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        tty_port_destroy(&port);
 292}
 293module_exit(bfin_jc_exit);
 294
 295#if defined(CONFIG_BFIN_JTAG_COMM_CONSOLE) || defined(CONFIG_EARLY_PRINTK)
 296static void
 297bfin_jc_straight_buffer_write(const char *buf, unsigned count)
 298{
 299        unsigned ate = 0;
 300        while (bfin_read_DBGSTAT() & EMUDOF)
 301                continue;
 302        bfin_write_emudat(count);
 303        while (ate < count) {
 304                while (bfin_read_DBGSTAT() & EMUDOF)
 305                        continue;
 306                bfin_write_emudat_chars(buf[ate], buf[ate+1], buf[ate+2], buf[ate+3]);
 307                ate += 4;
 308        }
 309}
 310#endif
 311
 312#ifdef CONFIG_BFIN_JTAG_COMM_CONSOLE
 313static void
 314bfin_jc_console_write(struct console *co, const char *buf, unsigned count)
 315{
 316        if (bfin_jc_kthread == NULL)
 317                bfin_jc_straight_buffer_write(buf, count);
 318        else
 319                bfin_jc_circ_write(buf, count);
 320}
 321
 322static struct tty_driver *
 323bfin_jc_console_device(struct console *co, int *index)
 324{
 325        *index = co->index;
 326        return bfin_jc_driver;
 327}
 328
 329static struct console bfin_jc_console = {
 330        .name    = DEV_NAME,
 331        .write   = bfin_jc_console_write,
 332        .device  = bfin_jc_console_device,
 333        .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 334        .index   = -1,
 335};
 336
 337static int __init bfin_jc_console_init(void)
 338{
 339        register_console(&bfin_jc_console);
 340        return 0;
 341}
 342console_initcall(bfin_jc_console_init);
 343#endif
 344
 345#ifdef CONFIG_EARLY_PRINTK
 346static void __init
 347bfin_jc_early_write(struct console *co, const char *buf, unsigned int count)
 348{
 349        bfin_jc_straight_buffer_write(buf, count);
 350}
 351
 352static struct __initdata console bfin_jc_early_console = {
 353        .name   = "early_BFJC",
 354        .write   = bfin_jc_early_write,
 355        .flags   = CON_ANYTIME | CON_PRINTBUFFER,
 356        .index   = -1,
 357};
 358
 359struct console * __init
 360bfin_jc_early_init(unsigned int port, unsigned int cflag)
 361{
 362        return &bfin_jc_early_console;
 363}
 364#endif
 365
 366MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
 367MODULE_DESCRIPTION("TTY over Blackfin JTAG Communication");
 368MODULE_LICENSE("GPL");
 369
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