Re: [PATCH 05/22] drm/i915: Move generic link training code to a separate file

["Thulasimani, Sivakumar" <sivakumar.thulasimani@intel.com>]

Reviewed-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>

On 10/23/2015 3:31 PM, Ander Conselvan de Oliveira wrote:
> No functional changes, just moving code around.
>
> v2: Rebase
>
> Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
> ---
>   drivers/gpu/drm/i915/Makefile                 |   1 +
>   drivers/gpu/drm/i915/intel_dp.c               | 321 +------------------------
>   drivers/gpu/drm/i915/intel_dp_link_training.c | 327 ++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/intel_drv.h              |  16 ++
>   4 files changed, 353 insertions(+), 312 deletions(-)
>   create mode 100644 drivers/gpu/drm/i915/intel_dp_link_training.c
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 44d290a..0851de07 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -77,6 +77,7 @@ i915-y += dvo_ch7017.o \
>   	  dvo_tfp410.o \
>   	  intel_crt.o \
>   	  intel_ddi.o \
> +	  intel_dp_link_training.o \
>   	  intel_dp_mst.o \
>   	  intel_dp.o \
>   	  intel_dsi.o \
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 4ffb2e3..4b88823 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1189,7 +1189,7 @@ intel_dp_sink_rates(struct intel_dp *intel_dp, const int **sink_rates)
>   	return (intel_dp_max_link_bw(intel_dp) >> 3) + 1;
>   }
>   
> -static bool intel_dp_source_supports_hbr2(struct drm_device *dev)
> +bool intel_dp_source_supports_hbr2(struct drm_device *dev)
>   {
>   	/* WaDisableHBR2:skl */
>   	if (IS_SKL_REVID(dev, 0, SKL_REVID_B0))
> @@ -1365,8 +1365,8 @@ int intel_dp_rate_select(struct intel_dp *intel_dp, int rate)
>   	return rate_to_index(rate, intel_dp->sink_rates);
>   }
>   
> -static void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
> -				  uint8_t *link_bw, uint8_t *rate_select)
> +void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
> +			   uint8_t *link_bw, uint8_t *rate_select)
>   {
>   	if (intel_dp->num_sink_rates) {
>   		*link_bw = 0;
> @@ -3046,7 +3046,7 @@ intel_dp_dpcd_read_wake(struct drm_dp_aux *aux, unsigned int offset,
>    * Fetch AUX CH registers 0x202 - 0x207 which contain
>    * link status information
>    */
> -static bool
> +bool
>   intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE])
>   {
>   	return intel_dp_dpcd_read_wake(&intel_dp->aux,
> @@ -3056,7 +3056,7 @@ intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_
>   }
>   
>   /* These are source-specific values. */
> -static uint8_t
> +uint8_t
>   intel_dp_voltage_max(struct intel_dp *intel_dp)
>   {
>   	struct drm_device *dev = intel_dp_to_dev(intel_dp);
> @@ -3079,7 +3079,7 @@ intel_dp_voltage_max(struct intel_dp *intel_dp)
>   		return DP_TRAIN_VOLTAGE_SWING_LEVEL_2;
>   }
>   
> -static uint8_t
> +uint8_t
>   intel_dp_pre_emphasis_max(struct intel_dp *intel_dp, uint8_t voltage_swing)
>   {
>   	struct drm_device *dev = intel_dp_to_dev(intel_dp);
> @@ -3421,38 +3421,6 @@ static uint32_t chv_signal_levels(struct intel_dp *intel_dp)
>   	return 0;
>   }
>   
> -static void
> -intel_get_adjust_train(struct intel_dp *intel_dp,
> -		       const uint8_t link_status[DP_LINK_STATUS_SIZE])
> -{
> -	uint8_t v = 0;
> -	uint8_t p = 0;
> -	int lane;
> -	uint8_t voltage_max;
> -	uint8_t preemph_max;
> -
> -	for (lane = 0; lane < intel_dp->lane_count; lane++) {
> -		uint8_t this_v = drm_dp_get_adjust_request_voltage(link_status, lane);
> -		uint8_t this_p = drm_dp_get_adjust_request_pre_emphasis(link_status, lane);
> -
> -		if (this_v > v)
> -			v = this_v;
> -		if (this_p > p)
> -			p = this_p;
> -	}
> -
> -	voltage_max = intel_dp_voltage_max(intel_dp);
> -	if (v >= voltage_max)
> -		v = voltage_max | DP_TRAIN_MAX_SWING_REACHED;
> -
> -	preemph_max = intel_dp_pre_emphasis_max(intel_dp, v);
> -	if (p >= preemph_max)
> -		p = preemph_max | DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
> -
> -	for (lane = 0; lane < 4; lane++)
> -		intel_dp->train_set[lane] = v | p;
> -}
> -
>   static uint32_t
>   gen4_signal_levels(uint8_t train_set)
>   {
> @@ -3550,7 +3518,7 @@ gen7_edp_signal_levels(uint8_t train_set)
>   	}
>   }
>   
> -static void
> +void
>   intel_dp_set_signal_levels(struct intel_dp *intel_dp)
>   {
>   	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> @@ -3597,7 +3565,7 @@ intel_dp_set_signal_levels(struct intel_dp *intel_dp)
>   	POSTING_READ(intel_dp->output_reg);
>   }
>   
> -static void
> +void
>   intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
>   				       uint8_t dp_train_pat)
>   {
> @@ -3611,56 +3579,7 @@ intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
>   	POSTING_READ(intel_dp->output_reg);
>   }
>   
> -static bool
> -intel_dp_set_link_train(struct intel_dp *intel_dp,
> -			uint8_t dp_train_pat)
> -{
> -	uint8_t buf[sizeof(intel_dp->train_set) + 1];
> -	int ret, len;
> -
> -	intel_dp_program_link_training_pattern(intel_dp, dp_train_pat);
> -
> -	buf[0] = dp_train_pat;
> -	if ((dp_train_pat & DP_TRAINING_PATTERN_MASK) ==
> -	    DP_TRAINING_PATTERN_DISABLE) {
> -		/* don't write DP_TRAINING_LANEx_SET on disable */
> -		len = 1;
> -	} else {
> -		/* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
> -		memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
> -		len = intel_dp->lane_count + 1;
> -	}
> -
> -	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
> -				buf, len);
> -
> -	return ret == len;
> -}
> -
> -static bool
> -intel_dp_reset_link_train(struct intel_dp *intel_dp,
> -			uint8_t dp_train_pat)
> -{
> -	if (!intel_dp->train_set_valid)
> -		memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
> -	intel_dp_set_signal_levels(intel_dp);
> -	return intel_dp_set_link_train(intel_dp, dp_train_pat);
> -}
> -
> -static bool
> -intel_dp_update_link_train(struct intel_dp *intel_dp)
> -{
> -	int ret;
> -
> -	intel_dp_set_signal_levels(intel_dp);
> -
> -	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
> -				intel_dp->train_set, intel_dp->lane_count);
> -
> -	return ret == intel_dp->lane_count;
> -}
> -
> -static void intel_dp_set_idle_link_train(struct intel_dp *intel_dp)
> +void intel_dp_set_idle_link_train(struct intel_dp *intel_dp)
>   {
>   	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
>   	struct drm_device *dev = intel_dig_port->base.base.dev;
> @@ -3691,228 +3610,6 @@ static void intel_dp_set_idle_link_train(struct intel_dp *intel_dp)
>   		DRM_ERROR("Timed out waiting for DP idle patterns\n");
>   }
>   
> -/* Enable corresponding port and start training pattern 1 */
> -static void
> -intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
> -{
> -	struct drm_encoder *encoder = &dp_to_dig_port(intel_dp)->base.base;
> -	struct drm_device *dev = encoder->dev;
> -	int i;
> -	uint8_t voltage;
> -	int voltage_tries, loop_tries;
> -	uint8_t link_config[2];
> -	uint8_t link_bw, rate_select;
> -
> -	if (HAS_DDI(dev))
> -		intel_ddi_prepare_link_retrain(encoder);
> -
> -	intel_dp_compute_rate(intel_dp, intel_dp->link_rate,
> -			      &link_bw, &rate_select);
> -
> -	/* Write the link configuration data */
> -	link_config[0] = link_bw;
> -	link_config[1] = intel_dp->lane_count;
> -	if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
> -		link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
> -	drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
> -	if (intel_dp->num_sink_rates)
> -		drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
> -				  &rate_select, 1);
> -
> -	link_config[0] = 0;
> -	link_config[1] = DP_SET_ANSI_8B10B;
> -	drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
> -
> -	intel_dp->DP |= DP_PORT_EN;
> -
> -	/* clock recovery */
> -	if (!intel_dp_reset_link_train(intel_dp,
> -				       DP_TRAINING_PATTERN_1 |
> -				       DP_LINK_SCRAMBLING_DISABLE)) {
> -		DRM_ERROR("failed to enable link training\n");
> -		return;
> -	}
> -
> -	voltage = 0xff;
> -	voltage_tries = 0;
> -	loop_tries = 0;
> -	for (;;) {
> -		uint8_t link_status[DP_LINK_STATUS_SIZE];
> -
> -		drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
> -		if (!intel_dp_get_link_status(intel_dp, link_status)) {
> -			DRM_ERROR("failed to get link status\n");
> -			break;
> -		}
> -
> -		if (drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
> -			DRM_DEBUG_KMS("clock recovery OK\n");
> -			break;
> -		}
> -
> -		/*
> -		 * if we used previously trained voltage and pre-emphasis values
> -		 * and we don't get clock recovery, reset link training values
> -		 */
> -		if (intel_dp->train_set_valid) {
> -			DRM_DEBUG_KMS("clock recovery not ok, reset");
> -			/* clear the flag as we are not reusing train set */
> -			intel_dp->train_set_valid = false;
> -			if (!intel_dp_reset_link_train(intel_dp,
> -						       DP_TRAINING_PATTERN_1 |
> -						       DP_LINK_SCRAMBLING_DISABLE)) {
> -				DRM_ERROR("failed to enable link training\n");
> -				return;
> -			}
> -			continue;
> -		}
> -
> -		/* Check to see if we've tried the max voltage */
> -		for (i = 0; i < intel_dp->lane_count; i++)
> -			if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
> -				break;
> -		if (i == intel_dp->lane_count) {
> -			++loop_tries;
> -			if (loop_tries == 5) {
> -				DRM_ERROR("too many full retries, give up\n");
> -				break;
> -			}
> -			intel_dp_reset_link_train(intel_dp,
> -						  DP_TRAINING_PATTERN_1 |
> -						  DP_LINK_SCRAMBLING_DISABLE);
> -			voltage_tries = 0;
> -			continue;
> -		}
> -
> -		/* Check to see if we've tried the same voltage 5 times */
> -		if ((intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK) == voltage) {
> -			++voltage_tries;
> -			if (voltage_tries == 5) {
> -				DRM_ERROR("too many voltage retries, give up\n");
> -				break;
> -			}
> -		} else
> -			voltage_tries = 0;
> -		voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;
> -
> -		/* Update training set as requested by target */
> -		intel_get_adjust_train(intel_dp, link_status);
> -		if (!intel_dp_update_link_train(intel_dp)) {
> -			DRM_ERROR("failed to update link training\n");
> -			break;
> -		}
> -	}
> -}
> -
> -static void
> -intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
> -{
> -	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> -	struct drm_device *dev = dig_port->base.base.dev;
> -	bool channel_eq = false;
> -	int tries, cr_tries;
> -	uint32_t training_pattern = DP_TRAINING_PATTERN_2;
> -
> -	/*
> -	 * Training Pattern 3 for HBR2 or 1.2 devices that support it.
> -	 *
> -	 * Intel platforms that support HBR2 also support TPS3. TPS3 support is
> -	 * also mandatory for downstream devices that support HBR2.
> -	 *
> -	 * Due to WaDisableHBR2 SKL < B0 is the only exception where TPS3 is
> -	 * supported but still not enabled.
> -	 */
> -	if (intel_dp_source_supports_hbr2(dev) &&
> -	    drm_dp_tps3_supported(intel_dp->dpcd))
> -		training_pattern = DP_TRAINING_PATTERN_3;
> -	else if (intel_dp->link_rate == 540000)
> -		DRM_ERROR("5.4 Gbps link rate without HBR2/TPS3 support\n");
> -
> -	/* channel equalization */
> -	if (!intel_dp_set_link_train(intel_dp,
> -				     training_pattern |
> -				     DP_LINK_SCRAMBLING_DISABLE)) {
> -		DRM_ERROR("failed to start channel equalization\n");
> -		return;
> -	}
> -
> -	tries = 0;
> -	cr_tries = 0;
> -	channel_eq = false;
> -	for (;;) {
> -		uint8_t link_status[DP_LINK_STATUS_SIZE];
> -
> -		if (cr_tries > 5) {
> -			DRM_ERROR("failed to train DP, aborting\n");
> -			break;
> -		}
> -
> -		drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
> -		if (!intel_dp_get_link_status(intel_dp, link_status)) {
> -			DRM_ERROR("failed to get link status\n");
> -			break;
> -		}
> -
> -		/* Make sure clock is still ok */
> -		if (!drm_dp_clock_recovery_ok(link_status,
> -					      intel_dp->lane_count)) {
> -			intel_dp->train_set_valid = false;
> -			intel_dp_link_training_clock_recovery(intel_dp);
> -			intel_dp_set_link_train(intel_dp,
> -						training_pattern |
> -						DP_LINK_SCRAMBLING_DISABLE);
> -			cr_tries++;
> -			continue;
> -		}
> -
> -		if (drm_dp_channel_eq_ok(link_status,
> -					 intel_dp->lane_count)) {
> -			channel_eq = true;
> -			break;
> -		}
> -
> -		/* Try 5 times, then try clock recovery if that fails */
> -		if (tries > 5) {
> -			intel_dp->train_set_valid = false;
> -			intel_dp_link_training_clock_recovery(intel_dp);
> -			intel_dp_set_link_train(intel_dp,
> -						training_pattern |
> -						DP_LINK_SCRAMBLING_DISABLE);
> -			tries = 0;
> -			cr_tries++;
> -			continue;
> -		}
> -
> -		/* Update training set as requested by target */
> -		intel_get_adjust_train(intel_dp, link_status);
> -		if (!intel_dp_update_link_train(intel_dp)) {
> -			DRM_ERROR("failed to update link training\n");
> -			break;
> -		}
> -		++tries;
> -	}
> -
> -	intel_dp_set_idle_link_train(intel_dp);
> -
> -	if (channel_eq) {
> -		intel_dp->train_set_valid = true;
> -		DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
> -	}
> -}
> -
> -void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> -{
> -	intel_dp_set_link_train(intel_dp,
> -				DP_TRAINING_PATTERN_DISABLE);
> -}
> -
> -void
> -intel_dp_start_link_train(struct intel_dp *intel_dp)
> -{
> -	intel_dp_link_training_clock_recovery(intel_dp);
> -	intel_dp_link_training_channel_equalization(intel_dp);
> -}
> -
>   static void
>   intel_dp_link_down(struct intel_dp *intel_dp)
>   {
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> new file mode 100644
> index 0000000..53f9c14
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -0,0 +1,327 @@
> +/*
> + * Copyright © 2008-2015 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + */
> +
> +#include "intel_drv.h"
> +
> +static void
> +intel_get_adjust_train(struct intel_dp *intel_dp,
> +		       const uint8_t link_status[DP_LINK_STATUS_SIZE])
> +{
> +	uint8_t v = 0;
> +	uint8_t p = 0;
> +	int lane;
> +	uint8_t voltage_max;
> +	uint8_t preemph_max;
> +
> +	for (lane = 0; lane < intel_dp->lane_count; lane++) {
> +		uint8_t this_v = drm_dp_get_adjust_request_voltage(link_status, lane);
> +		uint8_t this_p = drm_dp_get_adjust_request_pre_emphasis(link_status, lane);
> +
> +		if (this_v > v)
> +			v = this_v;
> +		if (this_p > p)
> +			p = this_p;
> +	}
> +
> +	voltage_max = intel_dp_voltage_max(intel_dp);
> +	if (v >= voltage_max)
> +		v = voltage_max | DP_TRAIN_MAX_SWING_REACHED;
> +
> +	preemph_max = intel_dp_pre_emphasis_max(intel_dp, v);
> +	if (p >= preemph_max)
> +		p = preemph_max | DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
> +
> +	for (lane = 0; lane < 4; lane++)
> +		intel_dp->train_set[lane] = v | p;
> +}
> +
> +static bool
> +intel_dp_set_link_train(struct intel_dp *intel_dp,
> +			uint8_t dp_train_pat)
> +{
> +	uint8_t buf[sizeof(intel_dp->train_set) + 1];
> +	int ret, len;
> +
> +	intel_dp_program_link_training_pattern(intel_dp, dp_train_pat);
> +
> +	buf[0] = dp_train_pat;
> +	if ((dp_train_pat & DP_TRAINING_PATTERN_MASK) ==
> +	    DP_TRAINING_PATTERN_DISABLE) {
> +		/* don't write DP_TRAINING_LANEx_SET on disable */
> +		len = 1;
> +	} else {
> +		/* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
> +		memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
> +		len = intel_dp->lane_count + 1;
> +	}
> +
> +	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
> +				buf, len);
> +
> +	return ret == len;
> +}
> +
> +static bool
> +intel_dp_reset_link_train(struct intel_dp *intel_dp,
> +			uint8_t dp_train_pat)
> +{
> +	if (!intel_dp->train_set_valid)
> +		memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set));
> +	intel_dp_set_signal_levels(intel_dp);
> +	return intel_dp_set_link_train(intel_dp, dp_train_pat);
> +}
> +
> +static bool
> +intel_dp_update_link_train(struct intel_dp *intel_dp)
> +{
> +	int ret;
> +
> +	intel_dp_set_signal_levels(intel_dp);
> +
> +	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
> +				intel_dp->train_set, intel_dp->lane_count);
> +
> +	return ret == intel_dp->lane_count;
> +}
> +
> +/* Enable corresponding port and start training pattern 1 */
> +static void
> +intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
> +{
> +	struct drm_encoder *encoder = &dp_to_dig_port(intel_dp)->base.base;
> +	struct drm_device *dev = encoder->dev;
> +	int i;
> +	uint8_t voltage;
> +	int voltage_tries, loop_tries;
> +	uint8_t link_config[2];
> +	uint8_t link_bw, rate_select;
> +
> +	if (HAS_DDI(dev))
> +		intel_ddi_prepare_link_retrain(encoder);
> +
> +	intel_dp_compute_rate(intel_dp, intel_dp->link_rate,
> +			      &link_bw, &rate_select);
> +
> +	/* Write the link configuration data */
> +	link_config[0] = link_bw;
> +	link_config[1] = intel_dp->lane_count;
> +	if (drm_dp_enhanced_frame_cap(intel_dp->dpcd))
> +		link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
> +	drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
> +	if (intel_dp->num_sink_rates)
> +		drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
> +				  &rate_select, 1);
> +
> +	link_config[0] = 0;
> +	link_config[1] = DP_SET_ANSI_8B10B;
> +	drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
> +
> +	intel_dp->DP |= DP_PORT_EN;
> +
> +	/* clock recovery */
> +	if (!intel_dp_reset_link_train(intel_dp,
> +				       DP_TRAINING_PATTERN_1 |
> +				       DP_LINK_SCRAMBLING_DISABLE)) {
> +		DRM_ERROR("failed to enable link training\n");
> +		return;
> +	}
> +
> +	voltage = 0xff;
> +	voltage_tries = 0;
> +	loop_tries = 0;
> +	for (;;) {
> +		uint8_t link_status[DP_LINK_STATUS_SIZE];
> +
> +		drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
> +		if (!intel_dp_get_link_status(intel_dp, link_status)) {
> +			DRM_ERROR("failed to get link status\n");
> +			break;
> +		}
> +
> +		if (drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
> +			DRM_DEBUG_KMS("clock recovery OK\n");
> +			break;
> +		}
> +
> +		/*
> +		 * if we used previously trained voltage and pre-emphasis values
> +		 * and we don't get clock recovery, reset link training values
> +		 */
> +		if (intel_dp->train_set_valid) {
> +			DRM_DEBUG_KMS("clock recovery not ok, reset");
> +			/* clear the flag as we are not reusing train set */
> +			intel_dp->train_set_valid = false;
> +			if (!intel_dp_reset_link_train(intel_dp,
> +						       DP_TRAINING_PATTERN_1 |
> +						       DP_LINK_SCRAMBLING_DISABLE)) {
> +				DRM_ERROR("failed to enable link training\n");
> +				return;
> +			}
> +			continue;
> +		}
> +
> +		/* Check to see if we've tried the max voltage */
> +		for (i = 0; i < intel_dp->lane_count; i++)
> +			if ((intel_dp->train_set[i] & DP_TRAIN_MAX_SWING_REACHED) == 0)
> +				break;
> +		if (i == intel_dp->lane_count) {
> +			++loop_tries;
> +			if (loop_tries == 5) {
> +				DRM_ERROR("too many full retries, give up\n");
> +				break;
> +			}
> +			intel_dp_reset_link_train(intel_dp,
> +						  DP_TRAINING_PATTERN_1 |
> +						  DP_LINK_SCRAMBLING_DISABLE);
> +			voltage_tries = 0;
> +			continue;
> +		}
> +
> +		/* Check to see if we've tried the same voltage 5 times */
> +		if ((intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK) == voltage) {
> +			++voltage_tries;
> +			if (voltage_tries == 5) {
> +				DRM_ERROR("too many voltage retries, give up\n");
> +				break;
> +			}
> +		} else
> +			voltage_tries = 0;
> +		voltage = intel_dp->train_set[0] & DP_TRAIN_VOLTAGE_SWING_MASK;
> +
> +		/* Update training set as requested by target */
> +		intel_get_adjust_train(intel_dp, link_status);
> +		if (!intel_dp_update_link_train(intel_dp)) {
> +			DRM_ERROR("failed to update link training\n");
> +			break;
> +		}
> +	}
> +}
> +
> +static void
> +intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
> +{
> +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> +	struct drm_device *dev = dig_port->base.base.dev;
> +	bool channel_eq = false;
> +	int tries, cr_tries;
> +	uint32_t training_pattern = DP_TRAINING_PATTERN_2;
> +
> +	/*
> +	 * Training Pattern 3 for HBR2 or 1.2 devices that support it.
> +	 *
> +	 * Intel platforms that support HBR2 also support TPS3. TPS3 support is
> +	 * also mandatory for downstream devices that support HBR2.
> +	 *
> +	 * Due to WaDisableHBR2 SKL < B0 is the only exception where TPS3 is
> +	 * supported but still not enabled.
> +	 */
> +	if (intel_dp_source_supports_hbr2(dev) &&
> +	    drm_dp_tps3_supported(intel_dp->dpcd))
> +		training_pattern = DP_TRAINING_PATTERN_3;
> +	else if (intel_dp->link_rate == 540000)
> +		DRM_ERROR("5.4 Gbps link rate without HBR2/TPS3 support\n");
> +
> +	/* channel equalization */
> +	if (!intel_dp_set_link_train(intel_dp,
> +				     training_pattern |
> +				     DP_LINK_SCRAMBLING_DISABLE)) {
> +		DRM_ERROR("failed to start channel equalization\n");
> +		return;
> +	}
> +
> +	tries = 0;
> +	cr_tries = 0;
> +	channel_eq = false;
> +	for (;;) {
> +		uint8_t link_status[DP_LINK_STATUS_SIZE];
> +
> +		if (cr_tries > 5) {
> +			DRM_ERROR("failed to train DP, aborting\n");
> +			break;
> +		}
> +
> +		drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
> +		if (!intel_dp_get_link_status(intel_dp, link_status)) {
> +			DRM_ERROR("failed to get link status\n");
> +			break;
> +		}
> +
> +		/* Make sure clock is still ok */
> +		if (!drm_dp_clock_recovery_ok(link_status,
> +					      intel_dp->lane_count)) {
> +			intel_dp->train_set_valid = false;
> +			intel_dp_link_training_clock_recovery(intel_dp);
> +			intel_dp_set_link_train(intel_dp,
> +						training_pattern |
> +						DP_LINK_SCRAMBLING_DISABLE);
> +			cr_tries++;
> +			continue;
> +		}
> +
> +		if (drm_dp_channel_eq_ok(link_status,
> +					 intel_dp->lane_count)) {
> +			channel_eq = true;
> +			break;
> +		}
> +
> +		/* Try 5 times, then try clock recovery if that fails */
> +		if (tries > 5) {
> +			intel_dp->train_set_valid = false;
> +			intel_dp_link_training_clock_recovery(intel_dp);
> +			intel_dp_set_link_train(intel_dp,
> +						training_pattern |
> +						DP_LINK_SCRAMBLING_DISABLE);
> +			tries = 0;
> +			cr_tries++;
> +			continue;
> +		}
> +
> +		/* Update training set as requested by target */
> +		intel_get_adjust_train(intel_dp, link_status);
> +		if (!intel_dp_update_link_train(intel_dp)) {
> +			DRM_ERROR("failed to update link training\n");
> +			break;
> +		}
> +		++tries;
> +	}
> +
> +	intel_dp_set_idle_link_train(intel_dp);
> +
> +	if (channel_eq) {
> +		intel_dp->train_set_valid = true;
> +		DRM_DEBUG_KMS("Channel EQ done. DP Training successful\n");
> +	}
> +}
> +
> +void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> +{
> +	intel_dp_set_link_train(intel_dp,
> +				DP_TRAINING_PATTERN_DISABLE);
> +}
> +
> +void
> +intel_dp_start_link_train(struct intel_dp *intel_dp)
> +{
> +	intel_dp_link_training_clock_recovery(intel_dp);
> +	intel_dp_link_training_channel_equalization(intel_dp);
> +}
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 6790187..25ac5d2 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1236,6 +1236,22 @@ bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>   					 struct intel_digital_port *port);
>   void hsw_dp_set_ddi_pll_sel(struct intel_crtc_state *pipe_config);
>   
> +void
> +intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
> +				       uint8_t dp_train_pat);
> +void
> +intel_dp_set_signal_levels(struct intel_dp *intel_dp);
> +void intel_dp_set_idle_link_train(struct intel_dp *intel_dp);
> +uint8_t
> +intel_dp_voltage_max(struct intel_dp *intel_dp);
> +uint8_t
> +intel_dp_pre_emphasis_max(struct intel_dp *intel_dp, uint8_t voltage_swing);
> +void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
> +			   uint8_t *link_bw, uint8_t *rate_select);
> +bool intel_dp_source_supports_hbr2(struct drm_device *dev);
> +bool
> +intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE]);
> +
>   /* intel_dp_mst.c */
>   int intel_dp_mst_encoder_init(struct intel_digital_port *intel_dig_port, int conn_id);
>   void intel_dp_mst_encoder_cleanup(struct intel_digital_port *intel_dig_port);

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