drivers/gpu/drm/i915/intel_dp_i2c.c

   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/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/delay.h>
  26 #include <linux/slab.h>
  27 #include <linux/init.h>
  28 #include <linux/errno.h>
  29 #include <linux/sched.h>
  30 #include <linux/i2c.h>
  31 #include "intel_dp.h"
  32 #include "drmP.h"
  33
  34 /* Run a single AUX_CH I2C transaction, writing/reading data as necessary */
  35
  36 #define MODE_I2C_START  1
  37 #define MODE_I2C_WRITE  2
  38 #define MODE_I2C_READ   4
  39 #define MODE_I2C_STOP   8
  40
  41 static int
  42 i2c_algo_dp_aux_transaction(struct i2c_adapter *adapter, int mode,
  43                             uint8_t write_byte, uint8_t *read_byte)
  44 {
  45         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
  46         uint16_t address = algo_data->address;
  47         uint8_t msg[5];
  48         uint8_t reply[2];
  49         int msg_bytes;
  50         int reply_bytes;
  51         int ret;
  52
  53         /* Set up the command byte */
  54         if (mode & MODE_I2C_READ)
  55                 msg[0] = AUX_I2C_READ << 4;
  56         else
  57                 msg[0] = AUX_I2C_WRITE << 4;
  58
  59         if (!(mode & MODE_I2C_STOP))
  60                 msg[0] |= AUX_I2C_MOT << 4;
  61
  62         msg[1] = address >> 8;
  63         msg[2] = address;
  64
  65         switch (mode) {
  66         case MODE_I2C_WRITE:
  67                 msg[3] = 0;
  68                 msg[4] = write_byte;
  69                 msg_bytes = 5;
  70                 reply_bytes = 1;
  71                 break;
  72         case MODE_I2C_READ:
  73                 msg[3] = 0;
  74                 msg_bytes = 4;
  75                 reply_bytes = 2;
  76                 break;
  77         default:
  78                 msg_bytes = 3;
  79                 reply_bytes = 1;
  80                 break;
  81         }
  82
  83         for (;;) {
  84                 ret = (*algo_data->aux_ch)(adapter,
  85                                            msg, msg_bytes,
  86                                            reply, reply_bytes);
  87                 if (ret < 0) {
  88                         DRM_DEBUG("aux_ch failed %d\n", ret);
  89                         return ret;
  90                 }
  91                 switch (reply[0] & AUX_I2C_REPLY_MASK) {
  92                 case AUX_I2C_REPLY_ACK:
  93                         if (mode == MODE_I2C_READ) {
  94                                 *read_byte = reply[1];
  95                         }
  96                         return reply_bytes - 1;
  97                 case AUX_I2C_REPLY_NACK:
  98                         DRM_DEBUG("aux_ch nack\n");
  99                         return -EREMOTEIO;
 100                 case AUX_I2C_REPLY_DEFER:
 101                         DRM_DEBUG("aux_ch defer\n");
 102                         udelay(100);
 103                         break;
 104                 default:
 105                         DRM_ERROR("aux_ch invalid reply 0x%02x\n", reply[0]);
 106                         return -EREMOTEIO;
 107                 }
 108         }
 109 }
 110
 111 /*
 112  * I2C over AUX CH
 113  */
 114
 115 /*
 116  * Send the address. If the I2C link is running, this 'restarts'
 117  * the connection with the new address, this is used for doing
 118  * a write followed by a read (as needed for DDC)
 119  */
 120 static int
 121 i2c_algo_dp_aux_address(struct i2c_adapter *adapter, u16 address, bool reading)
 122 {
 123         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 124         int mode = MODE_I2C_START;
 125         int ret;
 126
 127         if (reading)
 128                 mode |= MODE_I2C_READ;
 129         else
 130                 mode |= MODE_I2C_WRITE;
 131         algo_data->address = address;
 132         algo_data->running = true;
 133         ret = i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
 134         return ret;
 135 }
 136
 137 /*
 138  * Stop the I2C transaction. This closes out the link, sending
 139  * a bare address packet with the MOT bit turned off
 140  */
 141 static void
 142 i2c_algo_dp_aux_stop(struct i2c_adapter *adapter, bool reading)
 143 {
 144         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 145         int mode = MODE_I2C_STOP;
 146
 147         if (reading)
 148                 mode |= MODE_I2C_READ;
 149         else
 150                 mode |= MODE_I2C_WRITE;
 151         if (algo_data->running) {
 152                 (void) i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
 153                 algo_data->running = false;
 154         }
 155 }
 156
 157 /*
 158  * Write a single byte to the current I2C address, the
 159  * the I2C link must be running or this returns -EIO
 160  */
 161 static int
 162 i2c_algo_dp_aux_put_byte(struct i2c_adapter *adapter, u8 byte)
 163 {
 164         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 165         int ret;
 166
 167         if (!algo_data->running)
 168                 return -EIO;
 169
 170         ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_WRITE, byte, NULL);
 171         return ret;
 172 }
 173
 174 /*
 175  * Read a single byte from the current I2C address, the
 176  * I2C link must be running or this returns -EIO
 177  */
 178 static int
 179 i2c_algo_dp_aux_get_byte(struct i2c_adapter *adapter, u8 *byte_ret)
 180 {
 181         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 182         int ret;
 183
 184         if (!algo_data->running)
 185                 return -EIO;
 186
 187         ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_READ, 0, byte_ret);
 188         return ret;
 189 }
 190
 191 static int
 192 i2c_algo_dp_aux_xfer(struct i2c_adapter *adapter,
 193                      struct i2c_msg *msgs,
 194                      int num)
 195 {
 196         int ret = 0;
 197         bool reading = false;
 198         int m;
 199         int b;
 200
 201         for (m = 0; m < num; m++) {
 202                 u16 len = msgs[m].len;
 203                 u8 *buf = msgs[m].buf;
 204                 reading = (msgs[m].flags & I2C_M_RD) != 0;
 205                 ret = i2c_algo_dp_aux_address(adapter, msgs[m].addr, reading);
 206                 if (ret < 0)
 207                         break;
 208                 if (reading) {
 209                         for (b = 0; b < len; b++) {
 210                                 ret = i2c_algo_dp_aux_get_byte(adapter, &buf[b]);
 211                                 if (ret < 0)
 212                                         break;
 213                         }
 214                 } else {
 215                         for (b = 0; b < len; b++) {
 216                                 ret = i2c_algo_dp_aux_put_byte(adapter, buf[b]);
 217                                 if (ret < 0)
 218                                         break;
 219                         }
 220                 }
 221                 if (ret < 0)
 222                         break;
 223         }
 224         if (ret >= 0)
 225                 ret = num;
 226         i2c_algo_dp_aux_stop(adapter, reading);
 227         DRM_DEBUG("dp_aux_xfer return %d\n", ret);
 228         return ret;
 229 }
 230
 231 static u32
 232 i2c_algo_dp_aux_functionality(struct i2c_adapter *adapter)
 233 {
 234         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 235                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 236                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 237                I2C_FUNC_10BIT_ADDR;
 238 }
 239
 240 static const struct i2c_algorithm i2c_dp_aux_algo = {
 241         .master_xfer    = i2c_algo_dp_aux_xfer,
 242         .functionality  = i2c_algo_dp_aux_functionality,
 243 };
 244
 245 static void
 246 i2c_dp_aux_reset_bus(struct i2c_adapter *adapter)
 247 {
 248         (void) i2c_algo_dp_aux_address(adapter, 0, false);
 249         (void) i2c_algo_dp_aux_stop(adapter, false);
 250
 251 }
 252
 253 static int
 254 i2c_dp_aux_prepare_bus(struct i2c_adapter *adapter)
 255 {
 256         adapter->algo = &i2c_dp_aux_algo;
 257         adapter->retries = 3;
 258         i2c_dp_aux_reset_bus(adapter);
 259         return 0;
 260 }
 261
 262 int
 263 i2c_dp_aux_add_bus(struct i2c_adapter *adapter)
 264 {
 265         int error;
 266
 267         error = i2c_dp_aux_prepare_bus(adapter);
 268         if (error)
 269                 return error;
 270         error = i2c_add_adapter(adapter);
 271         return error;
 272 }
 273 EXPORT_SYMBOL(i2c_dp_aux_add_bus);