drivers/gpu/drm/drm_dp_i2c_helper.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 "drm_dp_helper.h"
  32 #include "drmP.h"
  33
  34 /* Run a single AUX_CH I2C transaction, writing/reading data as necessary */
  35 static int
  36 i2c_algo_dp_aux_transaction(struct i2c_adapter *adapter, int mode,
  37                             uint8_t write_byte, uint8_t *read_byte)
  38 {
  39         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
  40         int ret;
  41
  42         ret = (*algo_data->aux_ch)(adapter, mode,
  43                                    write_byte, read_byte);
  44         return ret;
  45 }
  46
  47 /*
  48  * I2C over AUX CH
  49  */
  50
  51 /*
  52  * Send the address. If the I2C link is running, this 'restarts'
  53  * the connection with the new address, this is used for doing
  54  * a write followed by a read (as needed for DDC)
  55  */
  56 static int
  57 i2c_algo_dp_aux_address(struct i2c_adapter *adapter, u16 address, bool reading)
  58 {
  59         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
  60         int mode = MODE_I2C_START;
  61         int ret;
  62
  63         if (reading)
  64                 mode |= MODE_I2C_READ;
  65         else
  66                 mode |= MODE_I2C_WRITE;
  67         algo_data->address = address;
  68         algo_data->running = true;
  69         ret = i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
  70         return ret;
  71 }
  72
  73 /*
  74  * Stop the I2C transaction. This closes out the link, sending
  75  * a bare address packet with the MOT bit turned off
  76  */
  77 static void
  78 i2c_algo_dp_aux_stop(struct i2c_adapter *adapter, bool reading)
  79 {
  80         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
  81         int mode = MODE_I2C_STOP;
  82
  83         if (reading)
  84                 mode |= MODE_I2C_READ;
  85         else
  86                 mode |= MODE_I2C_WRITE;
  87         if (algo_data->running) {
  88                 (void) i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
  89                 algo_data->running = false;
  90         }
  91 }
  92
  93 /*
  94  * Write a single byte to the current I2C address, the
  95  * the I2C link must be running or this returns -EIO
  96  */
  97 static int
  98 i2c_algo_dp_aux_put_byte(struct i2c_adapter *adapter, u8 byte)
  99 {
 100         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 101         int ret;
 102
 103         if (!algo_data->running)
 104                 return -EIO;
 105
 106         ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_WRITE, byte, NULL);
 107         return ret;
 108 }
 109
 110 /*
 111  * Read a single byte from the current I2C address, the
 112  * I2C link must be running or this returns -EIO
 113  */
 114 static int
 115 i2c_algo_dp_aux_get_byte(struct i2c_adapter *adapter, u8 *byte_ret)
 116 {
 117         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 118         int ret;
 119
 120         if (!algo_data->running)
 121                 return -EIO;
 122
 123         ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_READ, 0, byte_ret);
 124         return ret;
 125 }
 126
 127 static int
 128 i2c_algo_dp_aux_xfer(struct i2c_adapter *adapter,
 129                      struct i2c_msg *msgs,
 130                      int num)
 131 {
 132         int ret = 0;
 133         bool reading = false;
 134         int m;
 135         int b;
 136
 137         for (m = 0; m < num; m++) {
 138                 u16 len = msgs[m].len;
 139                 u8 *buf = msgs[m].buf;
 140                 reading = (msgs[m].flags & I2C_M_RD) != 0;
 141                 ret = i2c_algo_dp_aux_address(adapter, msgs[m].addr, reading);
 142                 if (ret < 0)
 143                         break;
 144                 if (reading) {
 145                         for (b = 0; b < len; b++) {
 146                                 ret = i2c_algo_dp_aux_get_byte(adapter, &buf[b]);
 147                                 if (ret < 0)
 148                                         break;
 149                         }
 150                 } else {
 151                         for (b = 0; b < len; b++) {
 152                                 ret = i2c_algo_dp_aux_put_byte(adapter, buf[b]);
 153                                 if (ret < 0)
 154                                         break;
 155                         }
 156                 }
 157                 if (ret < 0)
 158                         break;
 159         }
 160         if (ret >= 0)
 161                 ret = num;
 162         i2c_algo_dp_aux_stop(adapter, reading);
 163         DRM_DEBUG_KMS("dp_aux_xfer return %d\n", ret);
 164         return ret;
 165 }
 166
 167 static u32
 168 i2c_algo_dp_aux_functionality(struct i2c_adapter *adapter)
 169 {
 170         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 171                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 172                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 173                I2C_FUNC_10BIT_ADDR;
 174 }
 175
 176 static const struct i2c_algorithm i2c_dp_aux_algo = {
 177         .master_xfer    = i2c_algo_dp_aux_xfer,
 178         .functionality  = i2c_algo_dp_aux_functionality,
 179 };
 180
 181 static void
 182 i2c_dp_aux_reset_bus(struct i2c_adapter *adapter)
 183 {
 184         (void) i2c_algo_dp_aux_address(adapter, 0, false);
 185         (void) i2c_algo_dp_aux_stop(adapter, false);
 186
 187 }
 188
 189 static int
 190 i2c_dp_aux_prepare_bus(struct i2c_adapter *adapter)
 191 {
 192         adapter->algo = &i2c_dp_aux_algo;
 193         adapter->retries = 3;
 194         i2c_dp_aux_reset_bus(adapter);
 195         return 0;
 196 }
 197
 198 int
 199 i2c_dp_aux_add_bus(struct i2c_adapter *adapter)
 200 {
 201         int error;
 202
 203         error = i2c_dp_aux_prepare_bus(adapter);
 204         if (error)
 205                 return error;
 206         error = i2c_add_adapter(adapter);
 207         return error;
 208 }
 209 EXPORT_SYMBOL(i2c_dp_aux_add_bus);