2 * Copyright © 2009 Keith Packard
4 * Permission to use, copy, modify, distribute, and sell this software and its
5 * documentation for any purpose is hereby granted without fee, provided that
6 * the above copyright notice appear in all copies and that both that copyright
7 * notice and this permission notice appear in supporting documentation, and
8 * that the name of the copyright holders not be used in advertising or
9 * publicity pertaining to distribution of the software without specific,
10 * written prior permission. The copyright holders make no representations
11 * about the suitability of this software for any purpose. It is provided "as
12 * is" without express or implied warranty.
14 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
15 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
16 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
17 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
18 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
19 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
23 #include <linux/kernel.h>
24 #include <linux/module.h>
25 #include <linux/delay.h>
26 #include <linux/init.h>
27 #include <linux/errno.h>
28 #include <linux/sched.h>
29 #include <linux/i2c.h>
30 #include <drm/drm_dp_helper.h>
36 * These functions contain some common logic and helpers at various abstraction
37 * levels to deal with Display Port sink devices and related things like DP aux
38 * channel transfers, EDID reading over DP aux channels, decoding certain DPCD
42 /* Helpers for DP link training */
43 static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r)
45 return link_status[r - DP_LANE0_1_STATUS];
48 static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE],
51 int i = DP_LANE0_1_STATUS + (lane >> 1);
52 int s = (lane & 1) * 4;
53 u8 l = dp_link_status(link_status, i);
54 return (l >> s) & 0xf;
57 bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
64 lane_align = dp_link_status(link_status,
65 DP_LANE_ALIGN_STATUS_UPDATED);
66 if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0)
68 for (lane = 0; lane < lane_count; lane++) {
69 lane_status = dp_get_lane_status(link_status, lane);
70 if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS)
75 EXPORT_SYMBOL(drm_dp_channel_eq_ok);
77 bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
83 for (lane = 0; lane < lane_count; lane++) {
84 lane_status = dp_get_lane_status(link_status, lane);
85 if ((lane_status & DP_LANE_CR_DONE) == 0)
90 EXPORT_SYMBOL(drm_dp_clock_recovery_ok);
92 u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
95 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
97 DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT :
98 DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT);
99 u8 l = dp_link_status(link_status, i);
101 return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT;
103 EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage);
105 u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
108 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
109 int s = ((lane & 1) ?
110 DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT :
111 DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT);
112 u8 l = dp_link_status(link_status, i);
114 return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT;
116 EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
118 void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
119 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
122 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
124 EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
126 void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
127 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
130 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
132 EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
134 u8 drm_dp_link_rate_to_bw_code(int link_rate)
139 return DP_LINK_BW_1_62;
141 return DP_LINK_BW_2_7;
143 return DP_LINK_BW_5_4;
146 EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code);
148 int drm_dp_bw_code_to_link_rate(u8 link_bw)
151 case DP_LINK_BW_1_62:
160 EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);
162 #define AUX_RETRY_INTERVAL 500 /* us */
167 * The DisplayPort AUX channel is an abstraction to allow generic, driver-
168 * independent access to AUX functionality. Drivers can take advantage of
169 * this by filling in the fields of the drm_dp_aux structure.
171 * Transactions are described using a hardware-independent drm_dp_aux_msg
172 * structure, which is passed into a driver's .transfer() implementation.
173 * Both native and I2C-over-AUX transactions are supported.
176 static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
177 unsigned int offset, void *buffer, size_t size)
179 struct drm_dp_aux_msg msg;
183 memset(&msg, 0, sizeof(msg));
184 msg.address = offset;
185 msg.request = request;
190 * The specification doesn't give any recommendation on how often to
191 * retry native transactions. We used to retry 7 times like for
192 * aux i2c transactions but real world devices this wasn't
193 * sufficient, bump to 32 which makes Dell 4k monitors happier.
195 for (retry = 0; retry < 32; retry++) {
197 mutex_lock(&aux->hw_mutex);
198 err = aux->transfer(aux, &msg);
199 mutex_unlock(&aux->hw_mutex);
208 switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
209 case DP_AUX_NATIVE_REPLY_ACK:
214 case DP_AUX_NATIVE_REPLY_NACK:
217 case DP_AUX_NATIVE_REPLY_DEFER:
218 usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
223 DRM_DEBUG_KMS("too many retries, giving up\n");
228 * drm_dp_dpcd_read() - read a series of bytes from the DPCD
229 * @aux: DisplayPort AUX channel
230 * @offset: address of the (first) register to read
231 * @buffer: buffer to store the register values
232 * @size: number of bytes in @buffer
234 * Returns the number of bytes transferred on success, or a negative error
235 * code on failure. -EIO is returned if the request was NAKed by the sink or
236 * if the retry count was exceeded. If not all bytes were transferred, this
237 * function returns -EPROTO. Errors from the underlying AUX channel transfer
238 * function, with the exception of -EBUSY (which causes the transaction to
239 * be retried), are propagated to the caller.
241 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
242 void *buffer, size_t size)
244 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
247 EXPORT_SYMBOL(drm_dp_dpcd_read);
250 * drm_dp_dpcd_write() - write a series of bytes to the DPCD
251 * @aux: DisplayPort AUX channel
252 * @offset: address of the (first) register to write
253 * @buffer: buffer containing the values to write
254 * @size: number of bytes in @buffer
256 * Returns the number of bytes transferred on success, or a negative error
257 * code on failure. -EIO is returned if the request was NAKed by the sink or
258 * if the retry count was exceeded. If not all bytes were transferred, this
259 * function returns -EPROTO. Errors from the underlying AUX channel transfer
260 * function, with the exception of -EBUSY (which causes the transaction to
261 * be retried), are propagated to the caller.
263 ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
264 void *buffer, size_t size)
266 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
269 EXPORT_SYMBOL(drm_dp_dpcd_write);
272 * drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207)
273 * @aux: DisplayPort AUX channel
274 * @status: buffer to store the link status in (must be at least 6 bytes)
276 * Returns the number of bytes transferred on success or a negative error
279 int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
280 u8 status[DP_LINK_STATUS_SIZE])
282 return drm_dp_dpcd_read(aux, DP_LANE0_1_STATUS, status,
283 DP_LINK_STATUS_SIZE);
285 EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
288 * drm_dp_link_probe() - probe a DisplayPort link for capabilities
289 * @aux: DisplayPort AUX channel
290 * @link: pointer to structure in which to return link capabilities
292 * The structure filled in by this function can usually be passed directly
293 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
294 * configure the link based on the link's capabilities.
296 * Returns 0 on success or a negative error code on failure.
298 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
303 memset(link, 0, sizeof(*link));
305 err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));
309 link->revision = values[0];
310 link->rate = drm_dp_bw_code_to_link_rate(values[1]);
311 link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;
313 if (values[2] & DP_ENHANCED_FRAME_CAP)
314 link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
318 EXPORT_SYMBOL(drm_dp_link_probe);
321 * drm_dp_link_power_up() - power up a DisplayPort link
322 * @aux: DisplayPort AUX channel
323 * @link: pointer to a structure containing the link configuration
325 * Returns 0 on success or a negative error code on failure.
327 int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
332 /* DP_SET_POWER register is only available on DPCD v1.1 and later */
333 if (link->revision < 0x11)
336 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
340 value &= ~DP_SET_POWER_MASK;
341 value |= DP_SET_POWER_D0;
343 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
348 * According to the DP 1.1 specification, a "Sink Device must exit the
349 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
350 * Control Field" (register 0x600).
352 usleep_range(1000, 2000);
356 EXPORT_SYMBOL(drm_dp_link_power_up);
359 * drm_dp_link_power_down() - power down a DisplayPort link
360 * @aux: DisplayPort AUX channel
361 * @link: pointer to a structure containing the link configuration
363 * Returns 0 on success or a negative error code on failure.
365 int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link)
370 /* DP_SET_POWER register is only available on DPCD v1.1 and later */
371 if (link->revision < 0x11)
374 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
378 value &= ~DP_SET_POWER_MASK;
379 value |= DP_SET_POWER_D3;
381 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
387 EXPORT_SYMBOL(drm_dp_link_power_down);
390 * drm_dp_link_configure() - configure a DisplayPort link
391 * @aux: DisplayPort AUX channel
392 * @link: pointer to a structure containing the link configuration
394 * Returns 0 on success or a negative error code on failure.
396 int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
401 values[0] = drm_dp_link_rate_to_bw_code(link->rate);
402 values[1] = link->num_lanes;
404 if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
405 values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
407 err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));
413 EXPORT_SYMBOL(drm_dp_link_configure);
416 * I2C-over-AUX implementation
419 static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)
421 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
422 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
423 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
428 * Transfer a single I2C-over-AUX message and handle various error conditions,
429 * retrying the transaction as appropriate. It is assumed that the
430 * aux->transfer function does not modify anything in the msg other than the
433 * Returns bytes transferred on success, or a negative error code on failure.
435 static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
437 unsigned int retry, defer_i2c;
441 * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device
442 * is required to retry at least seven times upon receiving AUX_DEFER
443 * before giving up the AUX transaction.
445 for (retry = 0, defer_i2c = 0; retry < (7 + defer_i2c); retry++) {
446 mutex_lock(&aux->hw_mutex);
447 ret = aux->transfer(aux, msg);
448 mutex_unlock(&aux->hw_mutex);
453 DRM_DEBUG_KMS("transaction failed: %d\n", ret);
458 switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) {
459 case DP_AUX_NATIVE_REPLY_ACK:
461 * For I2C-over-AUX transactions this isn't enough, we
462 * need to check for the I2C ACK reply.
466 case DP_AUX_NATIVE_REPLY_NACK:
467 DRM_DEBUG_KMS("native nack (result=%d, size=%zu)\n", ret, msg->size);
470 case DP_AUX_NATIVE_REPLY_DEFER:
471 DRM_DEBUG_KMS("native defer\n");
473 * We could check for I2C bit rate capabilities and if
474 * available adjust this interval. We could also be
475 * more careful with DP-to-legacy adapters where a
476 * long legacy cable may force very low I2C bit rates.
478 * For now just defer for long enough to hopefully be
479 * safe for all use-cases.
481 usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
485 DRM_ERROR("invalid native reply %#04x\n", msg->reply);
489 switch (msg->reply & DP_AUX_I2C_REPLY_MASK) {
490 case DP_AUX_I2C_REPLY_ACK:
492 * Both native ACK and I2C ACK replies received. We
493 * can assume the transfer was successful.
497 case DP_AUX_I2C_REPLY_NACK:
498 DRM_DEBUG_KMS("I2C nack (result=%d, size=%zu\n", ret, msg->size);
499 aux->i2c_nack_count++;
502 case DP_AUX_I2C_REPLY_DEFER:
503 DRM_DEBUG_KMS("I2C defer\n");
504 /* DP Compliance Test 4.2.2.5 Requirement:
505 * Must have at least 7 retries for I2C defers on the
506 * transaction to pass this test
508 aux->i2c_defer_count++;
511 usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
515 DRM_ERROR("invalid I2C reply %#04x\n", msg->reply);
520 DRM_DEBUG_KMS("too many retries, giving up\n");
525 * Keep retrying drm_dp_i2c_do_msg until all data has been transferred.
527 * Returns an error code on failure, or a recommended transfer size on success.
529 static int drm_dp_i2c_drain_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *orig_msg)
531 int err, ret = orig_msg->size;
532 struct drm_dp_aux_msg msg = *orig_msg;
534 while (msg.size > 0) {
535 err = drm_dp_i2c_do_msg(aux, &msg);
537 return err == 0 ? -EPROTO : err;
539 if (err < msg.size && err < ret) {
540 DRM_DEBUG_KMS("Partial I2C reply: requested %zu bytes got %d bytes\n",
553 * Bizlink designed DP->DVI-D Dual Link adapters require the I2C over AUX
554 * packets to be as large as possible. If not, the I2C transactions never
555 * succeed. Hence the default is maximum.
557 static int dp_aux_i2c_transfer_size __read_mostly = DP_AUX_MAX_PAYLOAD_BYTES;
558 module_param_unsafe(dp_aux_i2c_transfer_size, int, 0644);
559 MODULE_PARM_DESC(dp_aux_i2c_transfer_size,
560 "Number of bytes to transfer in a single I2C over DP AUX CH message, (1-16, default 16)");
562 static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
565 struct drm_dp_aux *aux = adapter->algo_data;
567 unsigned transfer_size;
568 struct drm_dp_aux_msg msg;
571 dp_aux_i2c_transfer_size = clamp(dp_aux_i2c_transfer_size, 1, DP_AUX_MAX_PAYLOAD_BYTES);
573 memset(&msg, 0, sizeof(msg));
575 for (i = 0; i < num; i++) {
576 msg.address = msgs[i].addr;
577 msg.request = (msgs[i].flags & I2C_M_RD) ?
580 msg.request |= DP_AUX_I2C_MOT;
581 /* Send a bare address packet to start the transaction.
582 * Zero sized messages specify an address only (bare
583 * address) transaction.
587 err = drm_dp_i2c_do_msg(aux, &msg);
590 /* We want each transaction to be as large as possible, but
591 * we'll go to smaller sizes if the hardware gives us a
594 transfer_size = dp_aux_i2c_transfer_size;
595 for (j = 0; j < msgs[i].len; j += msg.size) {
596 msg.buffer = msgs[i].buf + j;
597 msg.size = min(transfer_size, msgs[i].len - j);
599 err = drm_dp_i2c_drain_msg(aux, &msg);
609 /* Send a bare address packet to close out the transaction.
610 * Zero sized messages specify an address only (bare
611 * address) transaction.
613 msg.request &= ~DP_AUX_I2C_MOT;
616 (void)drm_dp_i2c_do_msg(aux, &msg);
621 static const struct i2c_algorithm drm_dp_i2c_algo = {
622 .functionality = drm_dp_i2c_functionality,
623 .master_xfer = drm_dp_i2c_xfer,
627 * drm_dp_aux_register() - initialise and register aux channel
628 * @aux: DisplayPort AUX channel
630 * Returns 0 on success or a negative error code on failure.
632 int drm_dp_aux_register(struct drm_dp_aux *aux)
634 mutex_init(&aux->hw_mutex);
636 aux->ddc.algo = &drm_dp_i2c_algo;
637 aux->ddc.algo_data = aux;
638 aux->ddc.retries = 3;
640 aux->ddc.class = I2C_CLASS_DDC;
641 aux->ddc.owner = THIS_MODULE;
642 aux->ddc.dev.parent = aux->dev;
643 aux->ddc.dev.of_node = aux->dev->of_node;
645 strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
646 sizeof(aux->ddc.name));
648 return i2c_add_adapter(&aux->ddc);
650 EXPORT_SYMBOL(drm_dp_aux_register);
653 * drm_dp_aux_unregister() - unregister an AUX adapter
654 * @aux: DisplayPort AUX channel
656 void drm_dp_aux_unregister(struct drm_dp_aux *aux)
658 i2c_del_adapter(&aux->ddc);
660 EXPORT_SYMBOL(drm_dp_aux_unregister);