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authorDave Airlie <airlied@redhat.com>2014-02-26 23:30:08 -0500
committerDave Airlie <airlied@redhat.com>2014-02-26 23:30:08 -0500
commit6ba6b7cdaf1a48b24c23c303871ffe1640a866e8 (patch)
tree0e67c7aad3b51a879c8d6ae07ae8276c29514b38
parentcfbf8d4857c26a8a307fb7cd258074c9dcd8c691 (diff)
parent88759686c702f1fbbb8e737e6231b64a9880db73 (diff)
Merge tag 'drm/dp-aux-for-3.15-rc1' of git://anongit.freedesktop.org/tegra/linux into drm-next
drm: DisplayPort AUX framework for v3.15-rc1 This series of patches implements a small framework that abstracts away some of the functionality that the DisplayPort AUX channel provides. It comes with a set of generic helpers that use the driver implementations to reduce code duplication. * tag 'drm/dp-aux-for-3.15-rc1' of git://anongit.freedesktop.org/tegra/linux: drm/dp: Allow registering AUX channels as I2C busses drm/dp: Add DisplayPort link helpers drm/dp: Add drm_dp_dpcd_read_link_status() drm/dp: Add AUX channel infrastructure
-rw-r--r--drivers/gpu/drm/drm_dp_helper.c395
-rw-r--r--include/drm/drm_dp_helper.h111
2 files changed, 506 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 9e978aae8972..35251af3b14e 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -346,3 +346,398 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw)
346 } 346 }
347} 347}
348EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate); 348EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);
349
350/**
351 * DOC: dp helpers
352 *
353 * The DisplayPort AUX channel is an abstraction to allow generic, driver-
354 * independent access to AUX functionality. Drivers can take advantage of
355 * this by filling in the fields of the drm_dp_aux structure.
356 *
357 * Transactions are described using a hardware-independent drm_dp_aux_msg
358 * structure, which is passed into a driver's .transfer() implementation.
359 * Both native and I2C-over-AUX transactions are supported.
360 */
361
362static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
363 unsigned int offset, void *buffer, size_t size)
364{
365 struct drm_dp_aux_msg msg;
366 unsigned int retry;
367 int err;
368
369 memset(&msg, 0, sizeof(msg));
370 msg.address = offset;
371 msg.request = request;
372 msg.buffer = buffer;
373 msg.size = size;
374
375 /*
376 * The specification doesn't give any recommendation on how often to
377 * retry native transactions, so retry 7 times like for I2C-over-AUX
378 * transactions.
379 */
380 for (retry = 0; retry < 7; retry++) {
381 err = aux->transfer(aux, &msg);
382 if (err < 0) {
383 if (err == -EBUSY)
384 continue;
385
386 return err;
387 }
388
389 if (err < size)
390 return -EPROTO;
391
392 switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
393 case DP_AUX_NATIVE_REPLY_ACK:
394 return err;
395
396 case DP_AUX_NATIVE_REPLY_NACK:
397 return -EIO;
398
399 case DP_AUX_NATIVE_REPLY_DEFER:
400 usleep_range(400, 500);
401 break;
402 }
403 }
404
405 DRM_ERROR("too many retries, giving up\n");
406 return -EIO;
407}
408
409/**
410 * drm_dp_dpcd_read() - read a series of bytes from the DPCD
411 * @aux: DisplayPort AUX channel
412 * @offset: address of the (first) register to read
413 * @buffer: buffer to store the register values
414 * @size: number of bytes in @buffer
415 *
416 * Returns the number of bytes transferred on success, or a negative error
417 * code on failure. -EIO is returned if the request was NAKed by the sink or
418 * if the retry count was exceeded. If not all bytes were transferred, this
419 * function returns -EPROTO. Errors from the underlying AUX channel transfer
420 * function, with the exception of -EBUSY (which causes the transaction to
421 * be retried), are propagated to the caller.
422 */
423ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
424 void *buffer, size_t size)
425{
426 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
427 size);
428}
429EXPORT_SYMBOL(drm_dp_dpcd_read);
430
431/**
432 * drm_dp_dpcd_write() - write a series of bytes to the DPCD
433 * @aux: DisplayPort AUX channel
434 * @offset: address of the (first) register to write
435 * @buffer: buffer containing the values to write
436 * @size: number of bytes in @buffer
437 *
438 * Returns the number of bytes transferred on success, or a negative error
439 * code on failure. -EIO is returned if the request was NAKed by the sink or
440 * if the retry count was exceeded. If not all bytes were transferred, this
441 * function returns -EPROTO. Errors from the underlying AUX channel transfer
442 * function, with the exception of -EBUSY (which causes the transaction to
443 * be retried), are propagated to the caller.
444 */
445ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
446 void *buffer, size_t size)
447{
448 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
449 size);
450}
451EXPORT_SYMBOL(drm_dp_dpcd_write);
452
453/**
454 * drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207)
455 * @aux: DisplayPort AUX channel
456 * @status: buffer to store the link status in (must be at least 6 bytes)
457 *
458 * Returns the number of bytes transferred on success or a negative error
459 * code on failure.
460 */
461int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
462 u8 status[DP_LINK_STATUS_SIZE])
463{
464 return drm_dp_dpcd_read(aux, DP_LANE0_1_STATUS, status,
465 DP_LINK_STATUS_SIZE);
466}
467EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
468
469/**
470 * drm_dp_link_probe() - probe a DisplayPort link for capabilities
471 * @aux: DisplayPort AUX channel
472 * @link: pointer to structure in which to return link capabilities
473 *
474 * The structure filled in by this function can usually be passed directly
475 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
476 * configure the link based on the link's capabilities.
477 *
478 * Returns 0 on success or a negative error code on failure.
479 */
480int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
481{
482 u8 values[3];
483 int err;
484
485 memset(link, 0, sizeof(*link));
486
487 err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));
488 if (err < 0)
489 return err;
490
491 link->revision = values[0];
492 link->rate = drm_dp_bw_code_to_link_rate(values[1]);
493 link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;
494
495 if (values[2] & DP_ENHANCED_FRAME_CAP)
496 link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
497
498 return 0;
499}
500EXPORT_SYMBOL(drm_dp_link_probe);
501
502/**
503 * drm_dp_link_power_up() - power up a DisplayPort link
504 * @aux: DisplayPort AUX channel
505 * @link: pointer to a structure containing the link configuration
506 *
507 * Returns 0 on success or a negative error code on failure.
508 */
509int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
510{
511 u8 value;
512 int err;
513
514 /* DP_SET_POWER register is only available on DPCD v1.1 and later */
515 if (link->revision < 0x11)
516 return 0;
517
518 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
519 if (err < 0)
520 return err;
521
522 value &= ~DP_SET_POWER_MASK;
523 value |= DP_SET_POWER_D0;
524
525 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
526 if (err < 0)
527 return err;
528
529 /*
530 * According to the DP 1.1 specification, a "Sink Device must exit the
531 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
532 * Control Field" (register 0x600).
533 */
534 usleep_range(1000, 2000);
535
536 return 0;
537}
538EXPORT_SYMBOL(drm_dp_link_power_up);
539
540/**
541 * drm_dp_link_configure() - configure a DisplayPort link
542 * @aux: DisplayPort AUX channel
543 * @link: pointer to a structure containing the link configuration
544 *
545 * Returns 0 on success or a negative error code on failure.
546 */
547int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
548{
549 u8 values[2];
550 int err;
551
552 values[0] = drm_dp_link_rate_to_bw_code(link->rate);
553 values[1] = link->num_lanes;
554
555 if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
556 values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
557
558 err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));
559 if (err < 0)
560 return err;
561
562 return 0;
563}
564EXPORT_SYMBOL(drm_dp_link_configure);
565
566/*
567 * I2C-over-AUX implementation
568 */
569
570static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)
571{
572 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
573 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
574 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
575 I2C_FUNC_10BIT_ADDR;
576}
577
578/*
579 * Transfer a single I2C-over-AUX message and handle various error conditions,
580 * retrying the transaction as appropriate.
581 */
582static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
583{
584 unsigned int retry;
585 int err;
586
587 /*
588 * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device
589 * is required to retry at least seven times upon receiving AUX_DEFER
590 * before giving up the AUX transaction.
591 */
592 for (retry = 0; retry < 7; retry++) {
593 err = aux->transfer(aux, msg);
594 if (err < 0) {
595 if (err == -EBUSY)
596 continue;
597
598 DRM_DEBUG_KMS("transaction failed: %d\n", err);
599 return err;
600 }
601
602 if (err < msg->size)
603 return -EPROTO;
604
605 switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) {
606 case DP_AUX_NATIVE_REPLY_ACK:
607 /*
608 * For I2C-over-AUX transactions this isn't enough, we
609 * need to check for the I2C ACK reply.
610 */
611 break;
612
613 case DP_AUX_NATIVE_REPLY_NACK:
614 DRM_DEBUG_KMS("native nack\n");
615 return -EREMOTEIO;
616
617 case DP_AUX_NATIVE_REPLY_DEFER:
618 DRM_DEBUG_KMS("native defer");
619 /*
620 * We could check for I2C bit rate capabilities and if
621 * available adjust this interval. We could also be
622 * more careful with DP-to-legacy adapters where a
623 * long legacy cable may force very low I2C bit rates.
624 *
625 * For now just defer for long enough to hopefully be
626 * safe for all use-cases.
627 */
628 usleep_range(500, 600);
629 continue;
630
631 default:
632 DRM_ERROR("invalid native reply %#04x\n", msg->reply);
633 return -EREMOTEIO;
634 }
635
636 switch (msg->reply & DP_AUX_I2C_REPLY_MASK) {
637 case DP_AUX_I2C_REPLY_ACK:
638 /*
639 * Both native ACK and I2C ACK replies received. We
640 * can assume the transfer was successful.
641 */
642 return 0;
643
644 case DP_AUX_I2C_REPLY_NACK:
645 DRM_DEBUG_KMS("I2C nack\n");
646 return -EREMOTEIO;
647
648 case DP_AUX_I2C_REPLY_DEFER:
649 DRM_DEBUG_KMS("I2C defer\n");
650 usleep_range(400, 500);
651 continue;
652
653 default:
654 DRM_ERROR("invalid I2C reply %#04x\n", msg->reply);
655 return -EREMOTEIO;
656 }
657 }
658
659 DRM_ERROR("too many retries, giving up\n");
660 return -EREMOTEIO;
661}
662
663static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
664 int num)
665{
666 struct drm_dp_aux *aux = adapter->algo_data;
667 unsigned int i, j;
668
669 for (i = 0; i < num; i++) {
670 struct drm_dp_aux_msg msg;
671 int err;
672
673 /*
674 * Many hardware implementations support FIFOs larger than a
675 * single byte, but it has been empirically determined that
676 * transferring data in larger chunks can actually lead to
677 * decreased performance. Therefore each message is simply
678 * transferred byte-by-byte.
679 */
680 for (j = 0; j < msgs[i].len; j++) {
681 memset(&msg, 0, sizeof(msg));
682 msg.address = msgs[i].addr;
683
684 msg.request = (msgs[i].flags & I2C_M_RD) ?
685 DP_AUX_I2C_READ :
686 DP_AUX_I2C_WRITE;
687
688 /*
689 * All messages except the last one are middle-of-
690 * transfer messages.
691 */
692 if ((i < num - 1) || (j < msgs[i].len - 1))
693 msg.request |= DP_AUX_I2C_MOT;
694
695 msg.buffer = msgs[i].buf + j;
696 msg.size = 1;
697
698 err = drm_dp_i2c_do_msg(aux, &msg);
699 if (err < 0)
700 return err;
701 }
702 }
703
704 return num;
705}
706
707static const struct i2c_algorithm drm_dp_i2c_algo = {
708 .functionality = drm_dp_i2c_functionality,
709 .master_xfer = drm_dp_i2c_xfer,
710};
711
712/**
713 * drm_dp_aux_register_i2c_bus() - register an I2C adapter for I2C-over-AUX
714 * @aux: DisplayPort AUX channel
715 *
716 * Returns 0 on success or a negative error code on failure.
717 */
718int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux)
719{
720 aux->ddc.algo = &drm_dp_i2c_algo;
721 aux->ddc.algo_data = aux;
722 aux->ddc.retries = 3;
723
724 aux->ddc.class = I2C_CLASS_DDC;
725 aux->ddc.owner = THIS_MODULE;
726 aux->ddc.dev.parent = aux->dev;
727 aux->ddc.dev.of_node = aux->dev->of_node;
728
729 strncpy(aux->ddc.name, dev_name(aux->dev), sizeof(aux->ddc.name));
730
731 return i2c_add_adapter(&aux->ddc);
732}
733EXPORT_SYMBOL(drm_dp_aux_register_i2c_bus);
734
735/**
736 * drm_dp_aux_unregister_i2c_bus() - unregister an I2C-over-AUX adapter
737 * @aux: DisplayPort AUX channel
738 */
739void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux)
740{
741 i2c_del_adapter(&aux->ddc);
742}
743EXPORT_SYMBOL(drm_dp_aux_unregister_i2c_bus);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 1d09050a8c00..b7488c9849ad 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -291,6 +291,7 @@
291#define DP_SET_POWER 0x600 291#define DP_SET_POWER 0x600
292# define DP_SET_POWER_D0 0x1 292# define DP_SET_POWER_D0 0x1
293# define DP_SET_POWER_D3 0x2 293# define DP_SET_POWER_D3 0x2
294# define DP_SET_POWER_MASK 0x3
294 295
295#define DP_PSR_ERROR_STATUS 0x2006 /* XXX 1.2? */ 296#define DP_PSR_ERROR_STATUS 0x2006 /* XXX 1.2? */
296# define DP_PSR_LINK_CRC_ERROR (1 << 0) 297# define DP_PSR_LINK_CRC_ERROR (1 << 0)
@@ -398,4 +399,114 @@ drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
398 (dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP); 399 (dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP);
399} 400}
400 401
402/*
403 * DisplayPort AUX channel
404 */
405
406/**
407 * struct drm_dp_aux_msg - DisplayPort AUX channel transaction
408 * @address: address of the (first) register to access
409 * @request: contains the type of transaction (see DP_AUX_* macros)
410 * @reply: upon completion, contains the reply type of the transaction
411 * @buffer: pointer to a transmission or reception buffer
412 * @size: size of @buffer
413 */
414struct drm_dp_aux_msg {
415 unsigned int address;
416 u8 request;
417 u8 reply;
418 void *buffer;
419 size_t size;
420};
421
422/**
423 * struct drm_dp_aux - DisplayPort AUX channel
424 * @ddc: I2C adapter that can be used for I2C-over-AUX communication
425 * @dev: pointer to struct device that is the parent for this AUX channel
426 * @transfer: transfers a message representing a single AUX transaction
427 *
428 * The .dev field should be set to a pointer to the device that implements
429 * the AUX channel.
430 *
431 * Drivers provide a hardware-specific implementation of how transactions
432 * are executed via the .transfer() function. A pointer to a drm_dp_aux_msg
433 * structure describing the transaction is passed into this function. Upon
434 * success, the implementation should return the number of payload bytes
435 * that were transferred, or a negative error-code on failure. Helpers
436 * propagate errors from the .transfer() function, with the exception of
437 * the -EBUSY error, which causes a transaction to be retried. On a short,
438 * helpers will return -EPROTO to make it simpler to check for failure.
439 *
440 * An AUX channel can also be used to transport I2C messages to a sink. A
441 * typical application of that is to access an EDID that's present in the
442 * sink device. The .transfer() function can also be used to execute such
443 * transactions. The drm_dp_aux_register_i2c_bus() function registers an
444 * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers
445 * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter.
446 */
447struct drm_dp_aux {
448 struct i2c_adapter ddc;
449 struct device *dev;
450
451 ssize_t (*transfer)(struct drm_dp_aux *aux,
452 struct drm_dp_aux_msg *msg);
453};
454
455ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
456 void *buffer, size_t size);
457ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
458 void *buffer, size_t size);
459
460/**
461 * drm_dp_dpcd_readb() - read a single byte from the DPCD
462 * @aux: DisplayPort AUX channel
463 * @offset: address of the register to read
464 * @valuep: location where the value of the register will be stored
465 *
466 * Returns the number of bytes transferred (1) on success, or a negative
467 * error code on failure.
468 */
469static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux,
470 unsigned int offset, u8 *valuep)
471{
472 return drm_dp_dpcd_read(aux, offset, valuep, 1);
473}
474
475/**
476 * drm_dp_dpcd_writeb() - write a single byte to the DPCD
477 * @aux: DisplayPort AUX channel
478 * @offset: address of the register to write
479 * @value: value to write to the register
480 *
481 * Returns the number of bytes transferred (1) on success, or a negative
482 * error code on failure.
483 */
484static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,
485 unsigned int offset, u8 value)
486{
487 return drm_dp_dpcd_write(aux, offset, &value, 1);
488}
489
490int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
491 u8 status[DP_LINK_STATUS_SIZE]);
492
493/*
494 * DisplayPort link
495 */
496#define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)
497
498struct drm_dp_link {
499 unsigned char revision;
500 unsigned int rate;
501 unsigned int num_lanes;
502 unsigned long capabilities;
503};
504
505int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
506int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
507int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
508
509int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux);
510void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux);
511
401#endif /* _DRM_DP_HELPER_H_ */ 512#endif /* _DRM_DP_HELPER_H_ */