cb072eebfa
While probing the DisplayPort link, query the fast training capability. If supported, drivers can use the fast link training sequence instead of the more involved full link training sequence. Signed-off-by: Thierry Reding <treding@nvidia.com>
165 lines
3.8 KiB
C
165 lines
3.8 KiB
C
// SPDX-License-Identifier: MIT
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/*
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* Copyright (C) 2013-2019 NVIDIA Corporation
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* Copyright (C) 2015 Rob Clark
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*/
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#include <drm/drm_dp_helper.h>
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#include "dp.h"
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static void drm_dp_link_caps_reset(struct drm_dp_link_caps *caps)
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{
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caps->enhanced_framing = false;
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caps->fast_training = false;
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}
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void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest,
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const struct drm_dp_link_caps *src)
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{
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dest->enhanced_framing = src->enhanced_framing;
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dest->fast_training = src->fast_training;
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}
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static void drm_dp_link_reset(struct drm_dp_link *link)
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{
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if (!link)
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return;
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link->revision = 0;
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link->max_rate = 0;
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link->max_lanes = 0;
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drm_dp_link_caps_reset(&link->caps);
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link->rate = 0;
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link->lanes = 0;
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}
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/**
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* drm_dp_link_probe() - probe a DisplayPort link for capabilities
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* @aux: DisplayPort AUX channel
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* @link: pointer to structure in which to return link capabilities
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*
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* The structure filled in by this function can usually be passed directly
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* into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
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* configure the link based on the link's capabilities.
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*
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* Returns 0 on success or a negative error code on failure.
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*/
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int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
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{
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u8 dpcd[DP_RECEIVER_CAP_SIZE];
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int err;
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drm_dp_link_reset(link);
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err = drm_dp_dpcd_read(aux, DP_DPCD_REV, dpcd, sizeof(dpcd));
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if (err < 0)
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return err;
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link->revision = dpcd[DP_DPCD_REV];
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link->max_rate = drm_dp_max_link_rate(dpcd);
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link->max_lanes = drm_dp_max_lane_count(dpcd);
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link->caps.enhanced_framing = drm_dp_enhanced_frame_cap(dpcd);
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link->caps.fast_training = drm_dp_fast_training_cap(dpcd);
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link->rate = link->max_rate;
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link->lanes = link->max_lanes;
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return 0;
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}
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/**
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* drm_dp_link_power_up() - power up a DisplayPort link
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* @aux: DisplayPort AUX channel
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* @link: pointer to a structure containing the link configuration
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*
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* Returns 0 on success or a negative error code on failure.
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*/
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int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
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{
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u8 value;
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int err;
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/* DP_SET_POWER register is only available on DPCD v1.1 and later */
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if (link->revision < 0x11)
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return 0;
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err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
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if (err < 0)
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return err;
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value &= ~DP_SET_POWER_MASK;
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value |= DP_SET_POWER_D0;
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err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
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if (err < 0)
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return err;
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/*
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* According to the DP 1.1 specification, a "Sink Device must exit the
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* power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
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* Control Field" (register 0x600).
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*/
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usleep_range(1000, 2000);
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return 0;
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}
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/**
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* drm_dp_link_power_down() - power down a DisplayPort link
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* @aux: DisplayPort AUX channel
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* @link: pointer to a structure containing the link configuration
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*
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* Returns 0 on success or a negative error code on failure.
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*/
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int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link)
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{
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u8 value;
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int err;
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/* DP_SET_POWER register is only available on DPCD v1.1 and later */
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if (link->revision < 0x11)
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return 0;
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err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
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if (err < 0)
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return err;
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value &= ~DP_SET_POWER_MASK;
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value |= DP_SET_POWER_D3;
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err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
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if (err < 0)
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return err;
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return 0;
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}
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/**
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* drm_dp_link_configure() - configure a DisplayPort link
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* @aux: DisplayPort AUX channel
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* @link: pointer to a structure containing the link configuration
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*
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* Returns 0 on success or a negative error code on failure.
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*/
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int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
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{
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u8 values[2];
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int err;
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values[0] = drm_dp_link_rate_to_bw_code(link->rate);
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values[1] = link->lanes;
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if (link->caps.enhanced_framing)
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values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
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err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));
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if (err < 0)
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return err;
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return 0;
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}
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