Root/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
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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