b30edfd8d0
The DP Standard's recommendation is to use the LTTPR non-transparent mode link training if LTTPRs are detected, so let's do this. Besides power-saving, the advantages of this are that the maximum number of LTTPRs can only be used in non-transparent mode (the limit is 5-8 in transparent mode), and it provides a way to narrow down the reason for a link training failure to a given link segment. Non-transparent mode is probably also the mode that was tested the most by the industry. The changes in this patchset: - Pass the DP PHY that is currently link trained to all LT helpers, so that these can access the correct LTTPR/DPRX DPCD registers. - During LT take into account the LTTPR common lane rate/count and the per LTTPR-PHY vswing/pre-emph limits. - Switch to LTTPR non-transparent LT mode and train each link segment according to the sequence in DP Standard v2.0 (complete CR/EQ for each segment before continuing with the next segment). v2: - Switch to non-transparent mode during connector detection, which is required before reading the per-PHY LTTPR capabilities. - Move the DP_PHY_LTTPR() macro to drm_dp_helper.h (Ville) - Use the new drm_dp_dpcd_read_phy_link_status() instead of adding the same logic to intel_dp_get_link_status(). (Ville) - Make intel_dp_lttpr_phy_caps() return a pointer to the whole array instead of a pointer to its first element. (Ville) - Add the intel_dp_phy_is_downstream_of_source() helper. (Ville) - Add a code comment about the disable->enable quirk of non-transparent mode. - Add the intel_dp_training_pattern_set_reg() helper. - Fix checkpatch/sparse warns. Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Imre Deak <imre.deak@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201007170917.1764556-7-imre.deak@intel.com
32 lines
945 B
C
32 lines
945 B
C
/* SPDX-License-Identifier: MIT */
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/*
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* Copyright © 2019 Intel Corporation
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*/
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#ifndef __INTEL_DP_LINK_TRAINING_H__
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#define __INTEL_DP_LINK_TRAINING_H__
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#include <drm/drm_dp_helper.h>
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struct intel_crtc_state;
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struct intel_dp;
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int intel_dp_lttpr_init(struct intel_dp *intel_dp);
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void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
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const struct intel_crtc_state *crtc_state,
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enum drm_dp_phy dp_phy,
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const u8 link_status[DP_LINK_STATUS_SIZE]);
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void intel_dp_start_link_train(struct intel_dp *intel_dp,
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const struct intel_crtc_state *crtc_state);
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void intel_dp_stop_link_train(struct intel_dp *intel_dp,
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const struct intel_crtc_state *crtc_state);
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/* Get the TPSx symbol type of the value programmed to DP_TRAINING_PATTERN_SET */
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static inline u8 intel_dp_training_pattern_symbol(u8 pattern)
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{
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return pattern & ~DP_LINK_SCRAMBLING_DISABLE;
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}
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#endif /* __INTEL_DP_LINK_TRAINING_H__ */
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