1 // SPDX-License-Identifier: MIT
3 * Copyright (C) 2013-2019 NVIDIA Corporation
4 * Copyright (C) 2015 Rob Clark
7 #include <drm/drm_dp_helper.h>
11 static void drm_dp_link_reset(struct drm_dp_link *link)
19 link->capabilities = 0;
23 * drm_dp_link_probe() - probe a DisplayPort link for capabilities
24 * @aux: DisplayPort AUX channel
25 * @link: pointer to structure in which to return link capabilities
27 * The structure filled in by this function can usually be passed directly
28 * into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
29 * configure the link based on the link's capabilities.
31 * Returns 0 on success or a negative error code on failure.
33 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
38 drm_dp_link_reset(link);
40 err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));
44 link->revision = values[0];
45 link->rate = drm_dp_bw_code_to_link_rate(values[1]);
46 link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;
48 if (values[2] & DP_ENHANCED_FRAME_CAP)
49 link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
55 * drm_dp_link_power_up() - power up a DisplayPort link
56 * @aux: DisplayPort AUX channel
57 * @link: pointer to a structure containing the link configuration
59 * Returns 0 on success or a negative error code on failure.
61 int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
66 /* DP_SET_POWER register is only available on DPCD v1.1 and later */
67 if (link->revision < 0x11)
70 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
74 value &= ~DP_SET_POWER_MASK;
75 value |= DP_SET_POWER_D0;
77 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
82 * According to the DP 1.1 specification, a "Sink Device must exit the
83 * power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
84 * Control Field" (register 0x600).
86 usleep_range(1000, 2000);
92 * drm_dp_link_power_down() - power down a DisplayPort link
93 * @aux: DisplayPort AUX channel
94 * @link: pointer to a structure containing the link configuration
96 * Returns 0 on success or a negative error code on failure.
98 int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link)
103 /* DP_SET_POWER register is only available on DPCD v1.1 and later */
104 if (link->revision < 0x11)
107 err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
111 value &= ~DP_SET_POWER_MASK;
112 value |= DP_SET_POWER_D3;
114 err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
122 * drm_dp_link_configure() - configure a DisplayPort link
123 * @aux: DisplayPort AUX channel
124 * @link: pointer to a structure containing the link configuration
126 * Returns 0 on success or a negative error code on failure.
128 int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
133 values[0] = drm_dp_link_rate_to_bw_code(link->rate);
134 values[1] = link->num_lanes;
136 if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
137 values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
139 err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));