1 /* 2 * Copyright © 2009 Keith Packard 3 * 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. 13 * 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 20 * OF THIS SOFTWARE. 21 */ 22 23 #include <linux/export.h> 24 #include <drm/drmP.h> 25 #include <drm/drm_dp_helper.h> 26 27 28 /* Helpers for DP link training */ 29 static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r) 30 { 31 return link_status[r - DP_LANE0_1_STATUS]; 32 } 33 34 static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE], 35 int lane) 36 { 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; 41 } 42 43 bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE], 44 int lane_count) 45 { 46 u8 lane_align; 47 u8 lane_status; 48 int lane; 49 50 lane_align = dp_link_status(link_status, 51 DP_LANE_ALIGN_STATUS_UPDATED); 52 if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0) 53 return false; 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) 57 return false; 58 } 59 return true; 60 } 61 EXPORT_SYMBOL(drm_dp_channel_eq_ok); 62 63 bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE], 64 int lane_count) 65 { 66 int lane; 67 u8 lane_status; 68 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) 72 return false; 73 } 74 return true; 75 } 76 EXPORT_SYMBOL(drm_dp_clock_recovery_ok); 77 78 u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE], 79 int lane) 80 { 81 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1); 82 int s = ((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); 86 87 return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT; 88 } 89 EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage); 90 91 u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE], 92 int lane) 93 { 94 int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1); 95 int s = ((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); 99 100 return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT; 101 } 102 EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis); 103 104 void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { 105 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0) 106 udelay(100); 107 else 108 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4); 109 } 110 EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay); 111 112 void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { 113 if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0) 114 udelay(400); 115 else 116 mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4); 117 } 118 EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay); 119 120 u8 drm_dp_link_rate_to_bw_code(int link_rate) 121 { 122 switch (link_rate) { 123 case 162000: 124 default: 125 return DP_LINK_BW_1_62; 126 case 270000: 127 return DP_LINK_BW_2_7; 128 case 540000: 129 return DP_LINK_BW_5_4; 130 } 131 } 132 EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code); 133 134 int drm_dp_bw_code_to_link_rate(u8 link_bw) 135 { 136 switch (link_bw) { 137 case DP_LINK_BW_1_62: 138 default: 139 return 162000; 140 case DP_LINK_BW_2_7: 141 return 270000; 142 case DP_LINK_BW_5_4: 143 return 540000; 144 } 145 } 146 EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate); 147 148 /** 149 * DOC: dp helpers 150 * 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. 154 * 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. 158 */ 159 160 static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, 161 unsigned int offset, void *buffer, size_t size) 162 { 163 struct drm_dp_aux_msg msg; 164 unsigned int retry; 165 int err; 166 167 memset(&msg, 0, sizeof(msg)); 168 msg.address = offset; 169 msg.request = request; 170 msg.buffer = buffer; 171 msg.size = size; 172 173 /* 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 176 * transactions. 177 */ 178 for (retry = 0; retry < 7; retry++) { 179 180 mutex_lock(&aux->hw_mutex); 181 err = aux->transfer(aux, &msg); 182 mutex_unlock(&aux->hw_mutex); 183 if (err < 0) { 184 if (err == -EBUSY) 185 continue; 186 187 return err; 188 } 189 190 191 switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) { 192 case DP_AUX_NATIVE_REPLY_ACK: 193 if (err < size) 194 return -EPROTO; 195 return err; 196 197 case DP_AUX_NATIVE_REPLY_NACK: 198 return -EIO; 199 200 case DP_AUX_NATIVE_REPLY_DEFER: 201 usleep_range(400, 500); 202 break; 203 } 204 } 205 206 DRM_DEBUG_KMS("too many retries, giving up\n"); 207 return -EIO; 208 } 209 210 /** 211 * drm_dp_dpcd_read() - read a series of bytes from the DPCD 212 * @aux: DisplayPort AUX channel 213 * @offset: address of the (first) register to read 214 * @buffer: buffer to store the register values 215 * @size: number of bytes in @buffer 216 * 217 * Returns the number of bytes transferred on success, or a negative error 218 * code on failure. -EIO is returned if the request was NAKed by the sink or 219 * if the retry count was exceeded. If not all bytes were transferred, this 220 * function returns -EPROTO. Errors from the underlying AUX channel transfer 221 * function, with the exception of -EBUSY (which causes the transaction to 222 * be retried), are propagated to the caller. 223 */ 224 ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, 225 void *buffer, size_t size) 226 { 227 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, 228 size); 229 } 230 EXPORT_SYMBOL(drm_dp_dpcd_read); 231 232 /** 233 * drm_dp_dpcd_write() - write a series of bytes to the DPCD 234 * @aux: DisplayPort AUX channel 235 * @offset: address of the (first) register to write 236 * @buffer: buffer containing the values to write 237 * @size: number of bytes in @buffer 238 * 239 * Returns the number of bytes transferred on success, or a negative error 240 * code on failure. -EIO is returned if the request was NAKed by the sink or 241 * if the retry count was exceeded. If not all bytes were transferred, this 242 * function returns -EPROTO. Errors from the underlying AUX channel transfer 243 * function, with the exception of -EBUSY (which causes the transaction to 244 * be retried), are propagated to the caller. 245 */ 246 ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset, 247 void *buffer, size_t size) 248 { 249 return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer, 250 size); 251 } 252 EXPORT_SYMBOL(drm_dp_dpcd_write); 253 254