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
);
165 * The DisplayPort AUX channel is an abstraction to allow generic, driver-
166 * independent access to AUX functionality. Drivers can take advantage of
167 * this by filling in the fields of the drm_dp_aux structure.
169 * Transactions are described using a hardware-independent drm_dp_aux_msg
170 * structure, which is passed into a driver's .transfer() implementation.
171 * Both native and I2C-over-AUX transactions are supported.
174 static int drm_dp_dpcd_access(struct drm_dp_aux
*aux
, u8 request
,
175 unsigned int offset
, void *buffer
, size_t size
)
177 struct drm_dp_aux_msg msg
;
181 memset(&msg
, 0, sizeof(msg
));
182 msg
.address
= offset
;
183 msg
.request
= request
;
188 * The specification doesn't give any recommendation on how often to
189 * retry native transactions. We used to retry 7 times like for
190 * aux i2c transactions but real world devices this wasn't
191 * sufficient, bump to 32 which makes Dell 4k monitors happier.
193 for (retry
= 0; retry
< 32; retry
++) {
195 mutex_lock(&aux
->hw_mutex
);
196 err
= aux
->transfer(aux
, &msg
);
197 mutex_unlock(&aux
->hw_mutex
);
206 switch (msg
.reply
& DP_AUX_NATIVE_REPLY_MASK
) {
207 case DP_AUX_NATIVE_REPLY_ACK
:
212 case DP_AUX_NATIVE_REPLY_NACK
:
215 case DP_AUX_NATIVE_REPLY_DEFER
:
216 usleep_range(400, 500);
221 DRM_DEBUG_KMS("too many retries, giving up\n");
226 * drm_dp_dpcd_read() - read a series of bytes from the DPCD
227 * @aux: DisplayPort AUX channel
228 * @offset: address of the (first) register to read
229 * @buffer: buffer to store the register values
230 * @size: number of bytes in @buffer
232 * Returns the number of bytes transferred on success, or a negative error
233 * code on failure. -EIO is returned if the request was NAKed by the sink or
234 * if the retry count was exceeded. If not all bytes were transferred, this
235 * function returns -EPROTO. Errors from the underlying AUX channel transfer
236 * function, with the exception of -EBUSY (which causes the transaction to
237 * be retried), are propagated to the caller.
239 ssize_t
drm_dp_dpcd_read(struct drm_dp_aux
*aux
, unsigned int offset
,
240 void *buffer
, size_t size
)
242 return drm_dp_dpcd_access(aux
, DP_AUX_NATIVE_READ
, offset
, buffer
,
245 EXPORT_SYMBOL(drm_dp_dpcd_read
);
248 * drm_dp_dpcd_write() - write a series of bytes to the DPCD
249 * @aux: DisplayPort AUX channel
250 * @offset: address of the (first) register to write
251 * @buffer: buffer containing the values to write
252 * @size: number of bytes in @buffer
254 * Returns the number of bytes transferred on success, or a negative error
255 * code on failure. -EIO is returned if the request was NAKed by the sink or
256 * if the retry count was exceeded. If not all bytes were transferred, this
257 * function returns -EPROTO. Errors from the underlying AUX channel transfer
258 * function, with the exception of -EBUSY (which causes the transaction to
259 * be retried), are propagated to the caller.
261 ssize_t
drm_dp_dpcd_write(struct drm_dp_aux
*aux
, unsigned int offset
,
262 void *buffer
, size_t size
)
264 return drm_dp_dpcd_access(aux
, DP_AUX_NATIVE_WRITE
, offset
, buffer
,
267 EXPORT_SYMBOL(drm_dp_dpcd_write
);
270 * drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207)
271 * @aux: DisplayPort AUX channel
272 * @status: buffer to store the link status in (must be at least 6 bytes)
274 * Returns the number of bytes transferred on success or a negative error
277 int drm_dp_dpcd_read_link_status(struct drm_dp_aux
*aux
,
278 u8 status
[DP_LINK_STATUS_SIZE
])
280 return drm_dp_dpcd_read(aux
, DP_LANE0_1_STATUS
, status
,
281 DP_LINK_STATUS_SIZE
);
283 EXPORT_SYMBOL(drm_dp_dpcd_read_link_status
);
286 * drm_dp_link_probe() - probe a DisplayPort link for capabilities
287 * @aux: DisplayPort AUX channel
288 * @link: pointer to structure in which to return link capabilities
290 * The structure filled in by this function can usually be passed directly
291 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
292 * configure the link based on the link's capabilities.
294 * Returns 0 on success or a negative error code on failure.
296 int drm_dp_link_probe(struct drm_dp_aux
*aux
, struct drm_dp_link
*link
)
301 memset(link
, 0, sizeof(*link
));
303 err
= drm_dp_dpcd_read(aux
, DP_DPCD_REV
, values
, sizeof(values
));
307 link
->revision
= values
[0];
308 link
->rate
= drm_dp_bw_code_to_link_rate(values
[1]);
309 link
->num_lanes
= values
[2] & DP_MAX_LANE_COUNT_MASK
;
311 if (values
[2] & DP_ENHANCED_FRAME_CAP
)
312 link
->capabilities
|= DP_LINK_CAP_ENHANCED_FRAMING
;
316 EXPORT_SYMBOL(drm_dp_link_probe
);
319 * drm_dp_link_power_up() - power up a DisplayPort link
320 * @aux: DisplayPort AUX channel
321 * @link: pointer to a structure containing the link configuration
323 * Returns 0 on success or a negative error code on failure.
325 int drm_dp_link_power_up(struct drm_dp_aux
*aux
, struct drm_dp_link
*link
)
330 /* DP_SET_POWER register is only available on DPCD v1.1 and later */
331 if (link
->revision
< 0x11)
334 err
= drm_dp_dpcd_readb(aux
, DP_SET_POWER
, &value
);
338 value
&= ~DP_SET_POWER_MASK
;
339 value
|= DP_SET_POWER_D0
;
341 err
= drm_dp_dpcd_writeb(aux
, DP_SET_POWER
, value
);
346 * According to the DP 1.1 specification, a "Sink Device must exit the
347 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
348 * Control Field" (register 0x600).
350 usleep_range(1000, 2000);
354 EXPORT_SYMBOL(drm_dp_link_power_up
);
357 * drm_dp_link_power_down() - power down a DisplayPort link
358 * @aux: DisplayPort AUX channel
359 * @link: pointer to a structure containing the link configuration
361 * Returns 0 on success or a negative error code on failure.
363 int drm_dp_link_power_down(struct drm_dp_aux
*aux
, struct drm_dp_link
*link
)
368 /* DP_SET_POWER register is only available on DPCD v1.1 and later */
369 if (link
->revision
< 0x11)
372 err
= drm_dp_dpcd_readb(aux
, DP_SET_POWER
, &value
);
376 value
&= ~DP_SET_POWER_MASK
;
377 value
|= DP_SET_POWER_D3
;
379 err
= drm_dp_dpcd_writeb(aux
, DP_SET_POWER
, value
);
385 EXPORT_SYMBOL(drm_dp_link_power_down
);
388 * drm_dp_link_configure() - configure a DisplayPort link
389 * @aux: DisplayPort AUX channel
390 * @link: pointer to a structure containing the link configuration
392 * Returns 0 on success or a negative error code on failure.
394 int drm_dp_link_configure(struct drm_dp_aux
*aux
, struct drm_dp_link
*link
)
399 values
[0] = drm_dp_link_rate_to_bw_code(link
->rate
);
400 values
[1] = link
->num_lanes
;
402 if (link
->capabilities
& DP_LINK_CAP_ENHANCED_FRAMING
)
403 values
[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN
;
405 err
= drm_dp_dpcd_write(aux
, DP_LINK_BW_SET
, values
, sizeof(values
));
411 EXPORT_SYMBOL(drm_dp_link_configure
);
414 * I2C-over-AUX implementation
417 static u32
drm_dp_i2c_functionality(struct i2c_adapter
*adapter
)
419 return I2C_FUNC_I2C
| I2C_FUNC_SMBUS_EMUL
|
420 I2C_FUNC_SMBUS_READ_BLOCK_DATA
|
421 I2C_FUNC_SMBUS_BLOCK_PROC_CALL
|
426 * Transfer a single I2C-over-AUX message and handle various error conditions,
427 * retrying the transaction as appropriate. It is assumed that the
428 * aux->transfer function does not modify anything in the msg other than the
431 * Returns bytes transferred on success, or a negative error code on failure.
433 static int drm_dp_i2c_do_msg(struct drm_dp_aux
*aux
, struct drm_dp_aux_msg
*msg
)
435 unsigned int retry
, defer_i2c
;
439 * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device
440 * is required to retry at least seven times upon receiving AUX_DEFER
441 * before giving up the AUX transaction.
443 for (retry
= 0, defer_i2c
= 0; retry
< (7 + defer_i2c
); retry
++) {
444 mutex_lock(&aux
->hw_mutex
);
445 ret
= aux
->transfer(aux
, msg
);
446 mutex_unlock(&aux
->hw_mutex
);
451 DRM_DEBUG_KMS("transaction failed: %d\n", ret
);
456 switch (msg
->reply
& DP_AUX_NATIVE_REPLY_MASK
) {
457 case DP_AUX_NATIVE_REPLY_ACK
:
459 * For I2C-over-AUX transactions this isn't enough, we
460 * need to check for the I2C ACK reply.
464 case DP_AUX_NATIVE_REPLY_NACK
:
465 DRM_DEBUG_KMS("native nack (result=%d, size=%zu)\n", ret
, msg
->size
);
468 case DP_AUX_NATIVE_REPLY_DEFER
:
469 DRM_DEBUG_KMS("native defer\n");
471 * We could check for I2C bit rate capabilities and if
472 * available adjust this interval. We could also be
473 * more careful with DP-to-legacy adapters where a
474 * long legacy cable may force very low I2C bit rates.
476 * For now just defer for long enough to hopefully be
477 * safe for all use-cases.
479 usleep_range(500, 600);
483 DRM_ERROR("invalid native reply %#04x\n", msg
->reply
);
487 switch (msg
->reply
& DP_AUX_I2C_REPLY_MASK
) {
488 case DP_AUX_I2C_REPLY_ACK
:
490 * Both native ACK and I2C ACK replies received. We
491 * can assume the transfer was successful.
495 case DP_AUX_I2C_REPLY_NACK
:
496 DRM_DEBUG_KMS("I2C nack (result=%d, size=%zu\n", ret
, msg
->size
);
497 aux
->i2c_nack_count
++;
500 case DP_AUX_I2C_REPLY_DEFER
:
501 DRM_DEBUG_KMS("I2C defer\n");
502 /* DP Compliance Test 4.2.2.5 Requirement:
503 * Must have at least 7 retries for I2C defers on the
504 * transaction to pass this test
506 aux
->i2c_defer_count
++;
509 usleep_range(400, 500);
513 DRM_ERROR("invalid I2C reply %#04x\n", msg
->reply
);
518 DRM_DEBUG_KMS("too many retries, giving up\n");
523 * Keep retrying drm_dp_i2c_do_msg until all data has been transferred.
525 * Returns an error code on failure, or a recommended transfer size on success.
527 static int drm_dp_i2c_drain_msg(struct drm_dp_aux
*aux
, struct drm_dp_aux_msg
*orig_msg
)
529 int err
, ret
= orig_msg
->size
;
530 struct drm_dp_aux_msg msg
= *orig_msg
;
532 while (msg
.size
> 0) {
533 err
= drm_dp_i2c_do_msg(aux
, &msg
);
535 return err
== 0 ? -EPROTO
: err
;
537 if (err
< msg
.size
&& err
< ret
) {
538 DRM_DEBUG_KMS("Partial I2C reply: requested %zu bytes got %d bytes\n",
551 * Bizlink designed DP->DVI-D Dual Link adapters require the I2C over AUX
552 * packets to be as large as possible. If not, the I2C transactions never
553 * succeed. Hence the default is maximum.
555 static int dp_aux_i2c_transfer_size __read_mostly
= DP_AUX_MAX_PAYLOAD_BYTES
;
556 module_param_unsafe(dp_aux_i2c_transfer_size
, int, 0644);
557 MODULE_PARM_DESC(dp_aux_i2c_transfer_size
,
558 "Number of bytes to transfer in a single I2C over DP AUX CH message, (1-16, default 16)");
560 static int drm_dp_i2c_xfer(struct i2c_adapter
*adapter
, struct i2c_msg
*msgs
,
563 struct drm_dp_aux
*aux
= adapter
->algo_data
;
565 unsigned transfer_size
;
566 struct drm_dp_aux_msg msg
;
569 dp_aux_i2c_transfer_size
= clamp(dp_aux_i2c_transfer_size
, 1, DP_AUX_MAX_PAYLOAD_BYTES
);
571 memset(&msg
, 0, sizeof(msg
));
573 for (i
= 0; i
< num
; i
++) {
574 msg
.address
= msgs
[i
].addr
;
575 msg
.request
= (msgs
[i
].flags
& I2C_M_RD
) ?
578 msg
.request
|= DP_AUX_I2C_MOT
;
579 /* Send a bare address packet to start the transaction.
580 * Zero sized messages specify an address only (bare
581 * address) transaction.
585 err
= drm_dp_i2c_do_msg(aux
, &msg
);
588 /* We want each transaction to be as large as possible, but
589 * we'll go to smaller sizes if the hardware gives us a
592 transfer_size
= dp_aux_i2c_transfer_size
;
593 for (j
= 0; j
< msgs
[i
].len
; j
+= msg
.size
) {
594 msg
.buffer
= msgs
[i
].buf
+ j
;
595 msg
.size
= min(transfer_size
, msgs
[i
].len
- j
);
597 err
= drm_dp_i2c_drain_msg(aux
, &msg
);
607 /* Send a bare address packet to close out the transaction.
608 * Zero sized messages specify an address only (bare
609 * address) transaction.
611 msg
.request
&= ~DP_AUX_I2C_MOT
;
614 (void)drm_dp_i2c_do_msg(aux
, &msg
);
619 static const struct i2c_algorithm drm_dp_i2c_algo
= {
620 .functionality
= drm_dp_i2c_functionality
,
621 .master_xfer
= drm_dp_i2c_xfer
,
625 * drm_dp_aux_register() - initialise and register aux channel
626 * @aux: DisplayPort AUX channel
628 * Returns 0 on success or a negative error code on failure.
630 int drm_dp_aux_register(struct drm_dp_aux
*aux
)
632 mutex_init(&aux
->hw_mutex
);
634 aux
->ddc
.algo
= &drm_dp_i2c_algo
;
635 aux
->ddc
.algo_data
= aux
;
636 aux
->ddc
.retries
= 3;
638 aux
->ddc
.class = I2C_CLASS_DDC
;
639 aux
->ddc
.owner
= THIS_MODULE
;
640 aux
->ddc
.dev
.parent
= aux
->dev
;
641 aux
->ddc
.dev
.of_node
= aux
->dev
->of_node
;
643 strlcpy(aux
->ddc
.name
, aux
->name
? aux
->name
: dev_name(aux
->dev
),
644 sizeof(aux
->ddc
.name
));
646 return i2c_add_adapter(&aux
->ddc
);
648 EXPORT_SYMBOL(drm_dp_aux_register
);
651 * drm_dp_aux_unregister() - unregister an AUX adapter
652 * @aux: DisplayPort AUX channel
654 void drm_dp_aux_unregister(struct drm_dp_aux
*aux
)
656 i2c_del_adapter(&aux
->ddc
);
658 EXPORT_SYMBOL(drm_dp_aux_unregister
);