1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * OMAP1 Special OptimiSed Screen Interface support
4 *
5 * Copyright (C) 2004-2005 Nokia Corporation
6 * Author: Juha Yrjölä <juha.yrjola@nokia.com>
7 */
8 #include <linux/module.h>
9 #include <linux/mm.h>
10 #include <linux/clk.h>
11 #include <linux/irq.h>
12 #include <linux/io.h>
13 #include <linux/interrupt.h>
14
15 #include <linux/omap-dma.h>
16
17 #include "omapfb.h"
18 #include "lcdc.h"
19
20 #define MODULE_NAME "omapfb-sossi"
21
22 #define OMAP_SOSSI_BASE 0xfffbac00
23 #define SOSSI_ID_REG 0x00
24 #define SOSSI_INIT1_REG 0x04
25 #define SOSSI_INIT2_REG 0x08
26 #define SOSSI_INIT3_REG 0x0c
27 #define SOSSI_FIFO_REG 0x10
28 #define SOSSI_REOTABLE_REG 0x14
29 #define SOSSI_TEARING_REG 0x18
30 #define SOSSI_INIT1B_REG 0x1c
31 #define SOSSI_FIFOB_REG 0x20
32
33 #define DMA_GSCR 0xfffedc04
34 #define DMA_LCD_CCR 0xfffee3c2
35 #define DMA_LCD_CTRL 0xfffee3c4
36 #define DMA_LCD_LCH_CTRL 0xfffee3ea
37
38 #define CONF_SOSSI_RESET_R (1 << 23)
39
40 #define RD_ACCESS 0
41 #define WR_ACCESS 1
42
43 #define SOSSI_MAX_XMIT_BYTES (512 * 1024)
44
45 static struct {
46 void __iomem *base;
47 struct clk *fck;
48 unsigned long fck_hz;
49 spinlock_t lock;
50 int bus_pick_count;
51 int bus_pick_width;
52 int tearsync_mode;
53 int tearsync_line;
54 void (*lcdc_callback)(void *data);
55 void *lcdc_callback_data;
56 int vsync_dma_pending;
57 /* timing for read and write access */
58 int clk_div;
59 u8 clk_tw0[2];
60 u8 clk_tw1[2];
61 /*
62 * if last_access is the same as current we don't have to change
63 * the timings
64 */
65 int last_access;
66
67 struct omapfb_device *fbdev;
68 } sossi;
69
sossi_read_reg(int reg)70 static inline u32 sossi_read_reg(int reg)
71 {
72 return readl(sossi.base + reg);
73 }
74
sossi_read_reg16(int reg)75 static inline u16 sossi_read_reg16(int reg)
76 {
77 return readw(sossi.base + reg);
78 }
79
sossi_read_reg8(int reg)80 static inline u8 sossi_read_reg8(int reg)
81 {
82 return readb(sossi.base + reg);
83 }
84
sossi_write_reg(int reg,u32 value)85 static inline void sossi_write_reg(int reg, u32 value)
86 {
87 writel(value, sossi.base + reg);
88 }
89
sossi_write_reg16(int reg,u16 value)90 static inline void sossi_write_reg16(int reg, u16 value)
91 {
92 writew(value, sossi.base + reg);
93 }
94
sossi_write_reg8(int reg,u8 value)95 static inline void sossi_write_reg8(int reg, u8 value)
96 {
97 writeb(value, sossi.base + reg);
98 }
99
sossi_set_bits(int reg,u32 bits)100 static void sossi_set_bits(int reg, u32 bits)
101 {
102 sossi_write_reg(reg, sossi_read_reg(reg) | bits);
103 }
104
sossi_clear_bits(int reg,u32 bits)105 static void sossi_clear_bits(int reg, u32 bits)
106 {
107 sossi_write_reg(reg, sossi_read_reg(reg) & ~bits);
108 }
109
110 #define HZ_TO_PS(x) (1000000000 / (x / 1000))
111
ps_to_sossi_ticks(u32 ps,int div)112 static u32 ps_to_sossi_ticks(u32 ps, int div)
113 {
114 u32 clk_period = HZ_TO_PS(sossi.fck_hz) * div;
115 return (clk_period + ps - 1) / clk_period;
116 }
117
calc_rd_timings(struct extif_timings * t)118 static int calc_rd_timings(struct extif_timings *t)
119 {
120 u32 tw0, tw1;
121 int reon, reoff, recyc, actim;
122 int div = t->clk_div;
123
124 /*
125 * Make sure that after conversion it still holds that:
126 * reoff > reon, recyc >= reoff, actim > reon
127 */
128 reon = ps_to_sossi_ticks(t->re_on_time, div);
129 /* reon will be exactly one sossi tick */
130 if (reon > 1)
131 return -1;
132
133 reoff = ps_to_sossi_ticks(t->re_off_time, div);
134
135 if (reoff <= reon)
136 reoff = reon + 1;
137
138 tw0 = reoff - reon;
139 if (tw0 > 0x10)
140 return -1;
141
142 recyc = ps_to_sossi_ticks(t->re_cycle_time, div);
143 if (recyc <= reoff)
144 recyc = reoff + 1;
145
146 tw1 = recyc - tw0;
147 /* values less then 3 result in the SOSSI block resetting itself */
148 if (tw1 < 3)
149 tw1 = 3;
150 if (tw1 > 0x40)
151 return -1;
152
153 actim = ps_to_sossi_ticks(t->access_time, div);
154 if (actim < reoff)
155 actim++;
156 /*
157 * access time (data hold time) will be exactly one sossi
158 * tick
159 */
160 if (actim - reoff > 1)
161 return -1;
162
163 t->tim[0] = tw0 - 1;
164 t->tim[1] = tw1 - 1;
165
166 return 0;
167 }
168
calc_wr_timings(struct extif_timings * t)169 static int calc_wr_timings(struct extif_timings *t)
170 {
171 u32 tw0, tw1;
172 int weon, weoff, wecyc;
173 int div = t->clk_div;
174
175 /*
176 * Make sure that after conversion it still holds that:
177 * weoff > weon, wecyc >= weoff
178 */
179 weon = ps_to_sossi_ticks(t->we_on_time, div);
180 /* weon will be exactly one sossi tick */
181 if (weon > 1)
182 return -1;
183
184 weoff = ps_to_sossi_ticks(t->we_off_time, div);
185 if (weoff <= weon)
186 weoff = weon + 1;
187 tw0 = weoff - weon;
188 if (tw0 > 0x10)
189 return -1;
190
191 wecyc = ps_to_sossi_ticks(t->we_cycle_time, div);
192 if (wecyc <= weoff)
193 wecyc = weoff + 1;
194
195 tw1 = wecyc - tw0;
196 /* values less then 3 result in the SOSSI block resetting itself */
197 if (tw1 < 3)
198 tw1 = 3;
199 if (tw1 > 0x40)
200 return -1;
201
202 t->tim[2] = tw0 - 1;
203 t->tim[3] = tw1 - 1;
204
205 return 0;
206 }
207
_set_timing(int div,int tw0,int tw1)208 static void _set_timing(int div, int tw0, int tw1)
209 {
210 u32 l;
211
212 #ifdef VERBOSE
213 dev_dbg(sossi.fbdev->dev, "Using TW0 = %d, TW1 = %d, div = %d\n",
214 tw0 + 1, tw1 + 1, div);
215 #endif
216
217 clk_set_rate(sossi.fck, sossi.fck_hz / div);
218 clk_enable(sossi.fck);
219 l = sossi_read_reg(SOSSI_INIT1_REG);
220 l &= ~((0x0f << 20) | (0x3f << 24));
221 l |= (tw0 << 20) | (tw1 << 24);
222 sossi_write_reg(SOSSI_INIT1_REG, l);
223 clk_disable(sossi.fck);
224 }
225
_set_bits_per_cycle(int bus_pick_count,int bus_pick_width)226 static void _set_bits_per_cycle(int bus_pick_count, int bus_pick_width)
227 {
228 u32 l;
229
230 l = sossi_read_reg(SOSSI_INIT3_REG);
231 l &= ~0x3ff;
232 l |= ((bus_pick_count - 1) << 5) | ((bus_pick_width - 1) & 0x1f);
233 sossi_write_reg(SOSSI_INIT3_REG, l);
234 }
235
_set_tearsync_mode(int mode,unsigned line)236 static void _set_tearsync_mode(int mode, unsigned line)
237 {
238 u32 l;
239
240 l = sossi_read_reg(SOSSI_TEARING_REG);
241 l &= ~(((1 << 11) - 1) << 15);
242 l |= line << 15;
243 l &= ~(0x3 << 26);
244 l |= mode << 26;
245 sossi_write_reg(SOSSI_TEARING_REG, l);
246 if (mode)
247 sossi_set_bits(SOSSI_INIT2_REG, 1 << 6); /* TE logic */
248 else
249 sossi_clear_bits(SOSSI_INIT2_REG, 1 << 6);
250 }
251
set_timing(int access)252 static inline void set_timing(int access)
253 {
254 if (access != sossi.last_access) {
255 sossi.last_access = access;
256 _set_timing(sossi.clk_div,
257 sossi.clk_tw0[access], sossi.clk_tw1[access]);
258 }
259 }
260
sossi_start_transfer(void)261 static void sossi_start_transfer(void)
262 {
263 /* WE */
264 sossi_clear_bits(SOSSI_INIT2_REG, 1 << 4);
265 /* CS active low */
266 sossi_clear_bits(SOSSI_INIT1_REG, 1 << 30);
267 }
268
sossi_stop_transfer(void)269 static void sossi_stop_transfer(void)
270 {
271 /* WE */
272 sossi_set_bits(SOSSI_INIT2_REG, 1 << 4);
273 /* CS active low */
274 sossi_set_bits(SOSSI_INIT1_REG, 1 << 30);
275 }
276
wait_end_of_write(void)277 static void wait_end_of_write(void)
278 {
279 /* Before reading we must check if some writings are going on */
280 while (!(sossi_read_reg(SOSSI_INIT2_REG) & (1 << 3)));
281 }
282
send_data(const void * data,unsigned int len)283 static void send_data(const void *data, unsigned int len)
284 {
285 while (len >= 4) {
286 sossi_write_reg(SOSSI_FIFO_REG, *(const u32 *) data);
287 len -= 4;
288 data += 4;
289 }
290 while (len >= 2) {
291 sossi_write_reg16(SOSSI_FIFO_REG, *(const u16 *) data);
292 len -= 2;
293 data += 2;
294 }
295 while (len) {
296 sossi_write_reg8(SOSSI_FIFO_REG, *(const u8 *) data);
297 len--;
298 data++;
299 }
300 }
301
set_cycles(unsigned int len)302 static void set_cycles(unsigned int len)
303 {
304 unsigned long nr_cycles = len / (sossi.bus_pick_width / 8);
305
306 BUG_ON((nr_cycles - 1) & ~0x3ffff);
307
308 sossi_clear_bits(SOSSI_INIT1_REG, 0x3ffff);
309 sossi_set_bits(SOSSI_INIT1_REG, (nr_cycles - 1) & 0x3ffff);
310 }
311
sossi_convert_timings(struct extif_timings * t)312 static int sossi_convert_timings(struct extif_timings *t)
313 {
314 int r = 0;
315 int div = t->clk_div;
316
317 t->converted = 0;
318
319 if (div <= 0 || div > 8)
320 return -1;
321
322 /* no CS on SOSSI, so ignore cson, csoff, cs_pulsewidth */
323 if ((r = calc_rd_timings(t)) < 0)
324 return r;
325
326 if ((r = calc_wr_timings(t)) < 0)
327 return r;
328
329 t->tim[4] = div;
330
331 t->converted = 1;
332
333 return 0;
334 }
335
sossi_set_timings(const struct extif_timings * t)336 static void sossi_set_timings(const struct extif_timings *t)
337 {
338 BUG_ON(!t->converted);
339
340 sossi.clk_tw0[RD_ACCESS] = t->tim[0];
341 sossi.clk_tw1[RD_ACCESS] = t->tim[1];
342
343 sossi.clk_tw0[WR_ACCESS] = t->tim[2];
344 sossi.clk_tw1[WR_ACCESS] = t->tim[3];
345
346 sossi.clk_div = t->tim[4];
347 }
348
sossi_get_clk_info(u32 * clk_period,u32 * max_clk_div)349 static void sossi_get_clk_info(u32 *clk_period, u32 *max_clk_div)
350 {
351 *clk_period = HZ_TO_PS(sossi.fck_hz);
352 *max_clk_div = 8;
353 }
354
sossi_set_bits_per_cycle(int bpc)355 static void sossi_set_bits_per_cycle(int bpc)
356 {
357 int bus_pick_count, bus_pick_width;
358
359 /*
360 * We set explicitly the the bus_pick_count as well, although
361 * with remapping/reordering disabled it will be calculated by HW
362 * as (32 / bus_pick_width).
363 */
364 switch (bpc) {
365 case 8:
366 bus_pick_count = 4;
367 bus_pick_width = 8;
368 break;
369 case 16:
370 bus_pick_count = 2;
371 bus_pick_width = 16;
372 break;
373 default:
374 BUG();
375 return;
376 }
377 sossi.bus_pick_width = bus_pick_width;
378 sossi.bus_pick_count = bus_pick_count;
379 }
380
sossi_setup_tearsync(unsigned pin_cnt,unsigned hs_pulse_time,unsigned vs_pulse_time,int hs_pol_inv,int vs_pol_inv,int div)381 static int sossi_setup_tearsync(unsigned pin_cnt,
382 unsigned hs_pulse_time, unsigned vs_pulse_time,
383 int hs_pol_inv, int vs_pol_inv, int div)
384 {
385 int hs, vs;
386 u32 l;
387
388 if (pin_cnt != 1 || div < 1 || div > 8)
389 return -EINVAL;
390
391 hs = ps_to_sossi_ticks(hs_pulse_time, div);
392 vs = ps_to_sossi_ticks(vs_pulse_time, div);
393 if (vs < 8 || vs <= hs || vs >= (1 << 12))
394 return -EDOM;
395 vs /= 8;
396 vs--;
397 if (hs > 8)
398 hs = 8;
399 if (hs)
400 hs--;
401
402 dev_dbg(sossi.fbdev->dev,
403 "setup_tearsync: hs %d vs %d hs_inv %d vs_inv %d\n",
404 hs, vs, hs_pol_inv, vs_pol_inv);
405
406 clk_enable(sossi.fck);
407 l = sossi_read_reg(SOSSI_TEARING_REG);
408 l &= ~((1 << 15) - 1);
409 l |= vs << 3;
410 l |= hs;
411 if (hs_pol_inv)
412 l |= 1 << 29;
413 else
414 l &= ~(1 << 29);
415 if (vs_pol_inv)
416 l |= 1 << 28;
417 else
418 l &= ~(1 << 28);
419 sossi_write_reg(SOSSI_TEARING_REG, l);
420 clk_disable(sossi.fck);
421
422 return 0;
423 }
424
sossi_enable_tearsync(int enable,unsigned line)425 static int sossi_enable_tearsync(int enable, unsigned line)
426 {
427 int mode;
428
429 dev_dbg(sossi.fbdev->dev, "tearsync %d line %d\n", enable, line);
430 if (line >= 1 << 11)
431 return -EINVAL;
432 if (enable) {
433 if (line)
434 mode = 2; /* HS or VS */
435 else
436 mode = 3; /* VS only */
437 } else
438 mode = 0;
439 sossi.tearsync_line = line;
440 sossi.tearsync_mode = mode;
441
442 return 0;
443 }
444
sossi_write_command(const void * data,unsigned int len)445 static void sossi_write_command(const void *data, unsigned int len)
446 {
447 clk_enable(sossi.fck);
448 set_timing(WR_ACCESS);
449 _set_bits_per_cycle(sossi.bus_pick_count, sossi.bus_pick_width);
450 /* CMD#/DATA */
451 sossi_clear_bits(SOSSI_INIT1_REG, 1 << 18);
452 set_cycles(len);
453 sossi_start_transfer();
454 send_data(data, len);
455 sossi_stop_transfer();
456 wait_end_of_write();
457 clk_disable(sossi.fck);
458 }
459
sossi_write_data(const void * data,unsigned int len)460 static void sossi_write_data(const void *data, unsigned int len)
461 {
462 clk_enable(sossi.fck);
463 set_timing(WR_ACCESS);
464 _set_bits_per_cycle(sossi.bus_pick_count, sossi.bus_pick_width);
465 /* CMD#/DATA */
466 sossi_set_bits(SOSSI_INIT1_REG, 1 << 18);
467 set_cycles(len);
468 sossi_start_transfer();
469 send_data(data, len);
470 sossi_stop_transfer();
471 wait_end_of_write();
472 clk_disable(sossi.fck);
473 }
474
sossi_transfer_area(int width,int height,void (callback)(void * data),void * data)475 static void sossi_transfer_area(int width, int height,
476 void (callback)(void *data), void *data)
477 {
478 BUG_ON(callback == NULL);
479
480 sossi.lcdc_callback = callback;
481 sossi.lcdc_callback_data = data;
482
483 clk_enable(sossi.fck);
484 set_timing(WR_ACCESS);
485 _set_bits_per_cycle(sossi.bus_pick_count, sossi.bus_pick_width);
486 _set_tearsync_mode(sossi.tearsync_mode, sossi.tearsync_line);
487 /* CMD#/DATA */
488 sossi_set_bits(SOSSI_INIT1_REG, 1 << 18);
489 set_cycles(width * height * sossi.bus_pick_width / 8);
490
491 sossi_start_transfer();
492 if (sossi.tearsync_mode) {
493 /*
494 * Wait for the sync signal and start the transfer only
495 * then. We can't seem to be able to use HW sync DMA for
496 * this since LCD DMA shows huge latencies, as if it
497 * would ignore some of the DMA requests from SoSSI.
498 */
499 unsigned long flags;
500
501 spin_lock_irqsave(&sossi.lock, flags);
502 sossi.vsync_dma_pending++;
503 spin_unlock_irqrestore(&sossi.lock, flags);
504 } else
505 /* Just start the transfer right away. */
506 omap_enable_lcd_dma();
507 }
508
sossi_dma_callback(void * data)509 static void sossi_dma_callback(void *data)
510 {
511 omap_stop_lcd_dma();
512 sossi_stop_transfer();
513 clk_disable(sossi.fck);
514 sossi.lcdc_callback(sossi.lcdc_callback_data);
515 }
516
sossi_read_data(void * data,unsigned int len)517 static void sossi_read_data(void *data, unsigned int len)
518 {
519 clk_enable(sossi.fck);
520 set_timing(RD_ACCESS);
521 _set_bits_per_cycle(sossi.bus_pick_count, sossi.bus_pick_width);
522 /* CMD#/DATA */
523 sossi_set_bits(SOSSI_INIT1_REG, 1 << 18);
524 set_cycles(len);
525 sossi_start_transfer();
526 while (len >= 4) {
527 *(u32 *) data = sossi_read_reg(SOSSI_FIFO_REG);
528 len -= 4;
529 data += 4;
530 }
531 while (len >= 2) {
532 *(u16 *) data = sossi_read_reg16(SOSSI_FIFO_REG);
533 len -= 2;
534 data += 2;
535 }
536 while (len) {
537 *(u8 *) data = sossi_read_reg8(SOSSI_FIFO_REG);
538 len--;
539 data++;
540 }
541 sossi_stop_transfer();
542 clk_disable(sossi.fck);
543 }
544
sossi_match_irq(int irq,void * data)545 static irqreturn_t sossi_match_irq(int irq, void *data)
546 {
547 unsigned long flags;
548
549 spin_lock_irqsave(&sossi.lock, flags);
550 if (sossi.vsync_dma_pending) {
551 sossi.vsync_dma_pending--;
552 omap_enable_lcd_dma();
553 }
554 spin_unlock_irqrestore(&sossi.lock, flags);
555 return IRQ_HANDLED;
556 }
557
sossi_init(struct omapfb_device * fbdev)558 static int sossi_init(struct omapfb_device *fbdev)
559 {
560 u32 l, k;
561 struct clk *fck;
562 struct clk *dpll1out_ck;
563 int r;
564
565 sossi.base = ioremap(OMAP_SOSSI_BASE, SZ_1K);
566 if (!sossi.base) {
567 dev_err(fbdev->dev, "can't ioremap SoSSI\n");
568 return -ENOMEM;
569 }
570
571 sossi.fbdev = fbdev;
572 spin_lock_init(&sossi.lock);
573
574 dpll1out_ck = clk_get(fbdev->dev, "ck_dpll1out");
575 if (IS_ERR(dpll1out_ck)) {
576 dev_err(fbdev->dev, "can't get DPLL1OUT clock\n");
577 return PTR_ERR(dpll1out_ck);
578 }
579 /*
580 * We need the parent clock rate, which we might divide further
581 * depending on the timing requirements of the controller. See
582 * _set_timings.
583 */
584 sossi.fck_hz = clk_get_rate(dpll1out_ck);
585 clk_put(dpll1out_ck);
586
587 fck = clk_get(fbdev->dev, "ck_sossi");
588 if (IS_ERR(fck)) {
589 dev_err(fbdev->dev, "can't get SoSSI functional clock\n");
590 return PTR_ERR(fck);
591 }
592 sossi.fck = fck;
593
594 /* Reset and enable the SoSSI module */
595 l = omap_readl(MOD_CONF_CTRL_1);
596 l |= CONF_SOSSI_RESET_R;
597 omap_writel(l, MOD_CONF_CTRL_1);
598 l &= ~CONF_SOSSI_RESET_R;
599 omap_writel(l, MOD_CONF_CTRL_1);
600
601 clk_enable(sossi.fck);
602 l = omap_readl(ARM_IDLECT2);
603 l &= ~(1 << 8); /* DMACK_REQ */
604 omap_writel(l, ARM_IDLECT2);
605
606 l = sossi_read_reg(SOSSI_INIT2_REG);
607 /* Enable and reset the SoSSI block */
608 l |= (1 << 0) | (1 << 1);
609 sossi_write_reg(SOSSI_INIT2_REG, l);
610 /* Take SoSSI out of reset */
611 l &= ~(1 << 1);
612 sossi_write_reg(SOSSI_INIT2_REG, l);
613
614 sossi_write_reg(SOSSI_ID_REG, 0);
615 l = sossi_read_reg(SOSSI_ID_REG);
616 k = sossi_read_reg(SOSSI_ID_REG);
617
618 if (l != 0x55555555 || k != 0xaaaaaaaa) {
619 dev_err(fbdev->dev,
620 "invalid SoSSI sync pattern: %08x, %08x\n", l, k);
621 r = -ENODEV;
622 goto err;
623 }
624
625 if ((r = omap_lcdc_set_dma_callback(sossi_dma_callback, NULL)) < 0) {
626 dev_err(fbdev->dev, "can't get LCDC IRQ\n");
627 r = -ENODEV;
628 goto err;
629 }
630
631 l = sossi_read_reg(SOSSI_ID_REG); /* Component code */
632 l = sossi_read_reg(SOSSI_ID_REG);
633 dev_info(fbdev->dev, "SoSSI version %d.%d initialized\n",
634 l >> 16, l & 0xffff);
635
636 l = sossi_read_reg(SOSSI_INIT1_REG);
637 l |= (1 << 19); /* DMA_MODE */
638 l &= ~(1 << 31); /* REORDERING */
639 sossi_write_reg(SOSSI_INIT1_REG, l);
640
641 if ((r = request_irq(INT_1610_SoSSI_MATCH, sossi_match_irq,
642 IRQ_TYPE_EDGE_FALLING,
643 "sossi_match", sossi.fbdev->dev)) < 0) {
644 dev_err(sossi.fbdev->dev, "can't get SoSSI match IRQ\n");
645 goto err;
646 }
647
648 clk_disable(sossi.fck);
649 return 0;
650
651 err:
652 clk_disable(sossi.fck);
653 clk_put(sossi.fck);
654 return r;
655 }
656
sossi_cleanup(void)657 static void sossi_cleanup(void)
658 {
659 omap_lcdc_free_dma_callback();
660 clk_put(sossi.fck);
661 iounmap(sossi.base);
662 }
663
664 struct lcd_ctrl_extif omap1_ext_if = {
665 .init = sossi_init,
666 .cleanup = sossi_cleanup,
667 .get_clk_info = sossi_get_clk_info,
668 .convert_timings = sossi_convert_timings,
669 .set_timings = sossi_set_timings,
670 .set_bits_per_cycle = sossi_set_bits_per_cycle,
671 .setup_tearsync = sossi_setup_tearsync,
672 .enable_tearsync = sossi_enable_tearsync,
673 .write_command = sossi_write_command,
674 .read_data = sossi_read_data,
675 .write_data = sossi_write_data,
676 .transfer_area = sossi_transfer_area,
677
678 .max_transmit_size = SOSSI_MAX_XMIT_BYTES,
679 };
680
681