1 /*
2  * Copyright (c) 2012 Intel Corporation. All rights reserved.
3  * Copyright (c) 2006 - 2012 QLogic Corporation. All rights reserved.
4  * Copyright (c) 2003, 2004, 2005, 2006 PathScale, Inc. All rights reserved.
5  *
6  * This software is available to you under a choice of one of two
7  * licenses.  You may choose to be licensed under the terms of the GNU
8  * General Public License (GPL) Version 2, available from the file
9  * COPYING in the main directory of this source tree, or the
10  * OpenIB.org BSD license below:
11  *
12  *     Redistribution and use in source and binary forms, with or
13  *     without modification, are permitted provided that the following
14  *     conditions are met:
15  *
16  *      - Redistributions of source code must retain the above
17  *        copyright notice, this list of conditions and the following
18  *        disclaimer.
19  *
20  *      - Redistributions in binary form must reproduce the above
21  *        copyright notice, this list of conditions and the following
22  *        disclaimer in the documentation and/or other materials
23  *        provided with the distribution.
24  *
25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
26  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
27  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
28  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
29  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
30  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
31  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
32  * SOFTWARE.
33  */
34 
35 #include <linux/delay.h>
36 #include <linux/pci.h>
37 #include <linux/vmalloc.h>
38 
39 #include "qib.h"
40 
41 /*
42  * QLogic_IB "Two Wire Serial Interface" driver.
43  * Originally written for a not-quite-i2c serial eeprom, which is
44  * still used on some supported boards. Later boards have added a
45  * variety of other uses, most board-specific, so the bit-boffing
46  * part has been split off to this file, while the other parts
47  * have been moved to chip-specific files.
48  *
49  * We have also dropped all pretense of fully generic (e.g. pretend
50  * we don't know whether '1' is the higher voltage) interface, as
51  * the restrictions of the generic i2c interface (e.g. no access from
52  * driver itself) make it unsuitable for this use.
53  */
54 
55 #define READ_CMD 1
56 #define WRITE_CMD 0
57 
58 /**
59  * i2c_wait_for_writes - wait for a write
60  * @dd: the qlogic_ib device
61  *
62  * We use this instead of udelay directly, so we can make sure
63  * that previous register writes have been flushed all the way
64  * to the chip.  Since we are delaying anyway, the cost doesn't
65  * hurt, and makes the bit twiddling more regular
66  */
67 static void i2c_wait_for_writes(struct qib_devdata *dd)
68 {
69 	/*
70 	 * implicit read of EXTStatus is as good as explicit
71 	 * read of scratch, if all we want to do is flush
72 	 * writes.
73 	 */
74 	dd->f_gpio_mod(dd, 0, 0, 0);
75 	rmb(); /* inlined, so prevent compiler reordering */
76 }
77 
78 /*
79  * QSFP modules are allowed to hold SCL low for 500uSec. Allow twice that
80  * for "almost compliant" modules
81  */
82 #define SCL_WAIT_USEC 1000
83 
84 /* BUF_WAIT is time bus must be free between STOP or ACK and to next START.
85  * Should be 20, but some chips need more.
86  */
87 #define TWSI_BUF_WAIT_USEC 60
88 
89 static void scl_out(struct qib_devdata *dd, u8 bit)
90 {
91 	u32 mask;
92 
93 	udelay(1);
94 
95 	mask = 1UL << dd->gpio_scl_num;
96 
97 	/* SCL is meant to be bare-drain, so never set "OUT", just DIR */
98 	dd->f_gpio_mod(dd, 0, bit ? 0 : mask, mask);
99 
100 	/*
101 	 * Allow for slow slaves by simple
102 	 * delay for falling edge, sampling on rise.
103 	 */
104 	if (!bit)
105 		udelay(2);
106 	else {
107 		int rise_usec;
108 
109 		for (rise_usec = SCL_WAIT_USEC; rise_usec > 0; rise_usec -= 2) {
110 			if (mask & dd->f_gpio_mod(dd, 0, 0, 0))
111 				break;
112 			udelay(2);
113 		}
114 		if (rise_usec <= 0)
115 			qib_dev_err(dd, "SCL interface stuck low > %d uSec\n",
116 				    SCL_WAIT_USEC);
117 	}
118 	i2c_wait_for_writes(dd);
119 }
120 
121 static void sda_out(struct qib_devdata *dd, u8 bit)
122 {
123 	u32 mask;
124 
125 	mask = 1UL << dd->gpio_sda_num;
126 
127 	/* SDA is meant to be bare-drain, so never set "OUT", just DIR */
128 	dd->f_gpio_mod(dd, 0, bit ? 0 : mask, mask);
129 
130 	i2c_wait_for_writes(dd);
131 	udelay(2);
132 }
133 
134 static u8 sda_in(struct qib_devdata *dd, int wait)
135 {
136 	int bnum;
137 	u32 read_val, mask;
138 
139 	bnum = dd->gpio_sda_num;
140 	mask = (1UL << bnum);
141 	/* SDA is meant to be bare-drain, so never set "OUT", just DIR */
142 	dd->f_gpio_mod(dd, 0, 0, mask);
143 	read_val = dd->f_gpio_mod(dd, 0, 0, 0);
144 	if (wait)
145 		i2c_wait_for_writes(dd);
146 	return (read_val & mask) >> bnum;
147 }
148 
149 /**
150  * i2c_ackrcv - see if ack following write is true
151  * @dd: the qlogic_ib device
152  */
153 static int i2c_ackrcv(struct qib_devdata *dd)
154 {
155 	u8 ack_received;
156 
157 	/* AT ENTRY SCL = LOW */
158 	/* change direction, ignore data */
159 	ack_received = sda_in(dd, 1);
160 	scl_out(dd, 1);
161 	ack_received = sda_in(dd, 1) == 0;
162 	scl_out(dd, 0);
163 	return ack_received;
164 }
165 
166 static void stop_cmd(struct qib_devdata *dd);
167 
168 /**
169  * rd_byte - read a byte, sending STOP on last, else ACK
170  * @dd: the qlogic_ib device
171  * @last: identifies the last read
172  *
173  * Returns byte shifted out of device
174  */
175 static int rd_byte(struct qib_devdata *dd, int last)
176 {
177 	int bit_cntr, data;
178 
179 	data = 0;
180 
181 	for (bit_cntr = 7; bit_cntr >= 0; --bit_cntr) {
182 		data <<= 1;
183 		scl_out(dd, 1);
184 		data |= sda_in(dd, 0);
185 		scl_out(dd, 0);
186 	}
187 	if (last) {
188 		scl_out(dd, 1);
189 		stop_cmd(dd);
190 	} else {
191 		sda_out(dd, 0);
192 		scl_out(dd, 1);
193 		scl_out(dd, 0);
194 		sda_out(dd, 1);
195 	}
196 	return data;
197 }
198 
199 /**
200  * wr_byte - write a byte, one bit at a time
201  * @dd: the qlogic_ib device
202  * @data: the byte to write
203  *
204  * Returns 0 if we got the following ack, otherwise 1
205  */
206 static int wr_byte(struct qib_devdata *dd, u8 data)
207 {
208 	int bit_cntr;
209 	u8 bit;
210 
211 	for (bit_cntr = 7; bit_cntr >= 0; bit_cntr--) {
212 		bit = (data >> bit_cntr) & 1;
213 		sda_out(dd, bit);
214 		scl_out(dd, 1);
215 		scl_out(dd, 0);
216 	}
217 	return (!i2c_ackrcv(dd)) ? 1 : 0;
218 }
219 
220 /*
221  * issue TWSI start sequence:
222  * (both clock/data high, clock high, data low while clock is high)
223  */
224 static void start_seq(struct qib_devdata *dd)
225 {
226 	sda_out(dd, 1);
227 	scl_out(dd, 1);
228 	sda_out(dd, 0);
229 	udelay(1);
230 	scl_out(dd, 0);
231 }
232 
233 /**
234  * stop_seq - transmit the stop sequence
235  * @dd: the qlogic_ib device
236  *
237  * (both clock/data low, clock high, data high while clock is high)
238  */
239 static void stop_seq(struct qib_devdata *dd)
240 {
241 	scl_out(dd, 0);
242 	sda_out(dd, 0);
243 	scl_out(dd, 1);
244 	sda_out(dd, 1);
245 }
246 
247 /**
248  * stop_cmd - transmit the stop condition
249  * @dd: the qlogic_ib device
250  *
251  * (both clock/data low, clock high, data high while clock is high)
252  */
253 static void stop_cmd(struct qib_devdata *dd)
254 {
255 	stop_seq(dd);
256 	udelay(TWSI_BUF_WAIT_USEC);
257 }
258 
259 /**
260  * qib_twsi_reset - reset I2C communication
261  * @dd: the qlogic_ib device
262  */
263 
264 int qib_twsi_reset(struct qib_devdata *dd)
265 {
266 	int clock_cycles_left = 9;
267 	int was_high = 0;
268 	u32 pins, mask;
269 
270 	/* Both SCL and SDA should be high. If not, there
271 	 * is something wrong.
272 	 */
273 	mask = (1UL << dd->gpio_scl_num) | (1UL << dd->gpio_sda_num);
274 
275 	/*
276 	 * Force pins to desired innocuous state.
277 	 * This is the default power-on state with out=0 and dir=0,
278 	 * So tri-stated and should be floating high (barring HW problems)
279 	 */
280 	dd->f_gpio_mod(dd, 0, 0, mask);
281 
282 	/*
283 	 * Clock nine times to get all listeners into a sane state.
284 	 * If SDA does not go high at any point, we are wedged.
285 	 * One vendor recommends then issuing START followed by STOP.
286 	 * we cannot use our "normal" functions to do that, because
287 	 * if SCL drops between them, another vendor's part will
288 	 * wedge, dropping SDA and keeping it low forever, at the end of
289 	 * the next transaction (even if it was not the device addressed).
290 	 * So our START and STOP take place with SCL held high.
291 	 */
292 	while (clock_cycles_left--) {
293 		scl_out(dd, 0);
294 		scl_out(dd, 1);
295 		/* Note if SDA is high, but keep clocking to sync slave */
296 		was_high |= sda_in(dd, 0);
297 	}
298 
299 	if (was_high) {
300 		/*
301 		 * We saw a high, which we hope means the slave is sync'd.
302 		 * Issue START, STOP, pause for T_BUF.
303 		 */
304 
305 		pins = dd->f_gpio_mod(dd, 0, 0, 0);
306 		if ((pins & mask) != mask)
307 			qib_dev_err(dd, "GPIO pins not at rest: %d\n",
308 				    pins & mask);
309 		/* Drop SDA to issue START */
310 		udelay(1); /* Guarantee .6 uSec setup */
311 		sda_out(dd, 0);
312 		udelay(1); /* Guarantee .6 uSec hold */
313 		/* At this point, SCL is high, SDA low. Raise SDA for STOP */
314 		sda_out(dd, 1);
315 		udelay(TWSI_BUF_WAIT_USEC);
316 	}
317 
318 	return !was_high;
319 }
320 
321 #define QIB_TWSI_START 0x100
322 #define QIB_TWSI_STOP 0x200
323 
324 /* Write byte to TWSI, optionally prefixed with START or suffixed with
325  * STOP.
326  * returns 0 if OK (ACK received), else != 0
327  */
328 static int qib_twsi_wr(struct qib_devdata *dd, int data, int flags)
329 {
330 	int ret = 1;
331 
332 	if (flags & QIB_TWSI_START)
333 		start_seq(dd);
334 
335 	ret = wr_byte(dd, data); /* Leaves SCL low (from i2c_ackrcv()) */
336 
337 	if (flags & QIB_TWSI_STOP)
338 		stop_cmd(dd);
339 	return ret;
340 }
341 
342 /* Added functionality for IBA7220-based cards */
343 #define QIB_TEMP_DEV 0x98
344 
345 /*
346  * qib_twsi_blk_rd
347  * Formerly called qib_eeprom_internal_read, and only used for eeprom,
348  * but now the general interface for data transfer from twsi devices.
349  * One vestige of its former role is that it recognizes a device
350  * QIB_TWSI_NO_DEV and does the correct operation for the legacy part,
351  * which responded to all TWSI device codes, interpreting them as
352  * address within device. On all other devices found on board handled by
353  * this driver, the device is followed by a one-byte "address" which selects
354  * the "register" or "offset" within the device from which data should
355  * be read.
356  */
357 int qib_twsi_blk_rd(struct qib_devdata *dd, int dev, int addr,
358 		    void *buffer, int len)
359 {
360 	int ret;
361 	u8 *bp = buffer;
362 
363 	ret = 1;
364 
365 	if (dev == QIB_TWSI_NO_DEV) {
366 		/* legacy not-really-I2C */
367 		addr = (addr << 1) | READ_CMD;
368 		ret = qib_twsi_wr(dd, addr, QIB_TWSI_START);
369 	} else {
370 		/* Actual I2C */
371 		ret = qib_twsi_wr(dd, dev | WRITE_CMD, QIB_TWSI_START);
372 		if (ret) {
373 			stop_cmd(dd);
374 			ret = 1;
375 			goto bail;
376 		}
377 		/*
378 		 * SFF spec claims we do _not_ stop after the addr
379 		 * but simply issue a start with the "read" dev-addr.
380 		 * Since we are implicitely waiting for ACK here,
381 		 * we need t_buf (nominally 20uSec) before that start,
382 		 * and cannot rely on the delay built in to the STOP
383 		 */
384 		ret = qib_twsi_wr(dd, addr, 0);
385 		udelay(TWSI_BUF_WAIT_USEC);
386 
387 		if (ret) {
388 			qib_dev_err(dd,
389 				"Failed to write interface read addr %02X\n",
390 				addr);
391 			ret = 1;
392 			goto bail;
393 		}
394 		ret = qib_twsi_wr(dd, dev | READ_CMD, QIB_TWSI_START);
395 	}
396 	if (ret) {
397 		stop_cmd(dd);
398 		ret = 1;
399 		goto bail;
400 	}
401 
402 	/*
403 	 * block devices keeps clocking data out as long as we ack,
404 	 * automatically incrementing the address. Some have "pages"
405 	 * whose boundaries will not be crossed, but the handling
406 	 * of these is left to the caller, who is in a better
407 	 * position to know.
408 	 */
409 	while (len-- > 0) {
410 		/*
411 		 * Get and store data, sending ACK if length remaining,
412 		 * else STOP
413 		 */
414 		*bp++ = rd_byte(dd, !len);
415 	}
416 
417 	ret = 0;
418 
419 bail:
420 	return ret;
421 }
422 
423 /*
424  * qib_twsi_blk_wr
425  * Formerly called qib_eeprom_internal_write, and only used for eeprom,
426  * but now the general interface for data transfer to twsi devices.
427  * One vestige of its former role is that it recognizes a device
428  * QIB_TWSI_NO_DEV and does the correct operation for the legacy part,
429  * which responded to all TWSI device codes, interpreting them as
430  * address within device. On all other devices found on board handled by
431  * this driver, the device is followed by a one-byte "address" which selects
432  * the "register" or "offset" within the device to which data should
433  * be written.
434  */
435 int qib_twsi_blk_wr(struct qib_devdata *dd, int dev, int addr,
436 		    const void *buffer, int len)
437 {
438 	int sub_len;
439 	const u8 *bp = buffer;
440 	int max_wait_time, i;
441 	int ret = 1;
442 
443 	while (len > 0) {
444 		if (dev == QIB_TWSI_NO_DEV) {
445 			if (qib_twsi_wr(dd, (addr << 1) | WRITE_CMD,
446 					QIB_TWSI_START)) {
447 				goto failed_write;
448 			}
449 		} else {
450 			/* Real I2C */
451 			if (qib_twsi_wr(dd, dev | WRITE_CMD, QIB_TWSI_START))
452 				goto failed_write;
453 			ret = qib_twsi_wr(dd, addr, 0);
454 			if (ret) {
455 				qib_dev_err(dd,
456 					"Failed to write interface write addr %02X\n",
457 					addr);
458 				goto failed_write;
459 			}
460 		}
461 
462 		sub_len = min(len, 4);
463 		addr += sub_len;
464 		len -= sub_len;
465 
466 		for (i = 0; i < sub_len; i++)
467 			if (qib_twsi_wr(dd, *bp++, 0))
468 				goto failed_write;
469 
470 		stop_cmd(dd);
471 
472 		/*
473 		 * Wait for write complete by waiting for a successful
474 		 * read (the chip replies with a zero after the write
475 		 * cmd completes, and before it writes to the eeprom.
476 		 * The startcmd for the read will fail the ack until
477 		 * the writes have completed.   We do this inline to avoid
478 		 * the debug prints that are in the real read routine
479 		 * if the startcmd fails.
480 		 * We also use the proper device address, so it doesn't matter
481 		 * whether we have real eeprom_dev. Legacy likes any address.
482 		 */
483 		max_wait_time = 100;
484 		while (qib_twsi_wr(dd, dev | READ_CMD, QIB_TWSI_START)) {
485 			stop_cmd(dd);
486 			if (!--max_wait_time)
487 				goto failed_write;
488 		}
489 		/* now read (and ignore) the resulting byte */
490 		rd_byte(dd, 1);
491 	}
492 
493 	ret = 0;
494 	goto bail;
495 
496 failed_write:
497 	stop_cmd(dd);
498 	ret = 1;
499 
500 bail:
501 	return ret;
502 }
503