2 * Copyright © 2009 Keith Packard
4 * Permission to use, copy, modify, distribute, and sell this software and its
5 * documentation for any purpose is hereby granted without fee, provided that
6 * the above copyright notice appear in all copies and that both that copyright
7 * notice and this permission notice appear in supporting documentation, and
8 * that the name of the copyright holders not be used in advertising or
9 * publicity pertaining to distribution of the software without specific,
10 * written prior permission. The copyright holders make no representations
11 * about the suitability of this software for any purpose. It is provided "as
12 * is" without express or implied warranty.
14 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
15 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
16 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
17 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
18 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
19 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
23 #include <linux/export.h>
25 #include <drm/drm_dp_helper.h>
28 /* Helpers for DP link training */
29 static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r)
31 return link_status[r - DP_LANE0_1_STATUS];
34 static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE],
37 int i = DP_LANE0_1_STATUS + (lane >> 1);
38 int s = (lane & 1) * 4;
39 u8 l = dp_link_status(link_status, i);
40 return (l >> s) & 0xf;
43 bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
50 lane_align = dp_link_status(link_status,
51 DP_LANE_ALIGN_STATUS_UPDATED);
52 if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0)
54 for (lane = 0; lane < lane_count; lane++) {
55 lane_status = dp_get_lane_status(link_status, lane);
56 if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS)
61 EXPORT_SYMBOL(drm_dp_channel_eq_ok);
63 bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
69 for (lane = 0; lane < lane_count; lane++) {
70 lane_status = dp_get_lane_status(link_status, lane);
71 if ((lane_status & DP_LANE_CR_DONE) == 0)
76 EXPORT_SYMBOL(drm_dp_clock_recovery_ok);
78 u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
81 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
83 DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT :
84 DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT);
85 u8 l = dp_link_status(link_status, i);
87 return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT;
89 EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage);
91 u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
94 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
96 DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT :
97 DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT);
98 u8 l = dp_link_status(link_status, i);
100 return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT;
102 EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
104 void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
105 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
108 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
110 EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
112 void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
113 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
116 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
118 EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
120 u8 drm_dp_link_rate_to_bw_code(int link_rate)
125 return DP_LINK_BW_1_62;
127 return DP_LINK_BW_2_7;
129 return DP_LINK_BW_5_4;
132 EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code);
134 int drm_dp_bw_code_to_link_rate(u8 link_bw)
137 case DP_LINK_BW_1_62:
146 EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);
151 * The DisplayPort AUX channel is an abstraction to allow generic, driver-
152 * independent access to AUX functionality. Drivers can take advantage of
153 * this by filling in the fields of the drm_dp_aux structure.
155 * Transactions are described using a hardware-independent drm_dp_aux_msg
156 * structure, which is passed into a driver's .transfer() implementation.
157 * Both native and I2C-over-AUX transactions are supported.
160 static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
161 unsigned int offset, void *buffer, size_t size)
163 struct drm_dp_aux_msg msg;
167 memset(&msg, 0, sizeof(msg));
168 msg.address = offset;
169 msg.request = request;
174 * The specification doesn't give any recommendation on how often to
175 * retry native transactions, so retry 7 times like for I2C-over-AUX
178 for (retry = 0; retry < 7; retry++) {
180 mutex_lock(&aux->hw_mutex);
181 KKASSERT(aux->transfer != NULL);
182 err = aux->transfer(aux, &msg);
183 mutex_unlock(&aux->hw_mutex);
192 switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
193 case DP_AUX_NATIVE_REPLY_ACK:
198 case DP_AUX_NATIVE_REPLY_NACK:
201 case DP_AUX_NATIVE_REPLY_DEFER:
202 usleep_range(400, 500);
207 DRM_DEBUG_KMS("too many retries, giving up\n");
212 * drm_dp_dpcd_read() - read a series of bytes from the DPCD
213 * @aux: DisplayPort AUX channel
214 * @offset: address of the (first) register to read
215 * @buffer: buffer to store the register values
216 * @size: number of bytes in @buffer
218 * Returns the number of bytes transferred on success, or a negative error
219 * code on failure. -EIO is returned if the request was NAKed by the sink or
220 * if the retry count was exceeded. If not all bytes were transferred, this
221 * function returns -EPROTO. Errors from the underlying AUX channel transfer
222 * function, with the exception of -EBUSY (which causes the transaction to
223 * be retried), are propagated to the caller.
225 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
226 void *buffer, size_t size)
228 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
231 EXPORT_SYMBOL(drm_dp_dpcd_read);
234 * drm_dp_dpcd_write() - write a series of bytes to the DPCD
235 * @aux: DisplayPort AUX channel
236 * @offset: address of the (first) register to write
237 * @buffer: buffer containing the values to write
238 * @size: number of bytes in @buffer
240 * Returns the number of bytes transferred on success, or a negative error
241 * code on failure. -EIO is returned if the request was NAKed by the sink or
242 * if the retry count was exceeded. If not all bytes were transferred, this
243 * function returns -EPROTO. Errors from the underlying AUX channel transfer
244 * function, with the exception of -EBUSY (which causes the transaction to
245 * be retried), are propagated to the caller.
247 ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
248 void *buffer, size_t size)
250 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
253 EXPORT_SYMBOL(drm_dp_dpcd_write);
256 * drm_dp_aux_unregister() - unregister an AUX adapter
257 * @aux: DisplayPort AUX channel
259 void drm_dp_aux_unregister(struct drm_dp_aux *aux)
262 i2c_del_adapter(&aux->ddc);
265 EXPORT_SYMBOL(drm_dp_aux_unregister);