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/init.h>
  27 #include <linux/errno.h>
  28 #include <linux/sched.h>
  29 #include <linux/i2c.h>
  30 #include "drm_dp_helper.h"
  31 #include "drmP.h"
  32
  33 /* Run a single AUX_CH I2C transaction, writing/reading data as necessary */
  34 static int
  35 i2c_algo_dp_aux_transaction(struct i2c_adapter *adapter, int mode,
  36                             uint8_t write_byte, uint8_t *read_byte)
  37 {
  38         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
  39         int ret;
  40
  41         ret = (*algo_data->aux_ch)(adapter, mode,
  42                                    write_byte, read_byte);
  43         return ret;
  44 }
  45
  46 /*
  47  * I2C over AUX CH
  48  */
  49
  50 /*
  51  * Send the address. If the I2C link is running, this 'restarts'
  52  * the connection with the new address, this is used for doing
  53  * a write followed by a read (as needed for DDC)
  54  */
  55 static int
  56 i2c_algo_dp_aux_address(struct i2c_adapter *adapter, u16 address, bool reading)
  57 {
  58         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
  59         int mode = MODE_I2C_START;
  60         int ret;
  61
  62         if (reading)
  63                 mode |= MODE_I2C_READ;
  64         else
  65                 mode |= MODE_I2C_WRITE;
  66         algo_data->address = address;
  67         algo_data->running = true;
  68         ret = i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
  69         return ret;
  70 }
  71
  72 /*
  73  * Stop the I2C transaction. This closes out the link, sending
  74  * a bare address packet with the MOT bit turned off
  75  */
  76 static void
  77 i2c_algo_dp_aux_stop(struct i2c_adapter *adapter, bool reading)
  78 {
  79         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
  80         int mode = MODE_I2C_STOP;
  81
  82         if (reading)
  83                 mode |= MODE_I2C_READ;
  84         else
  85                 mode |= MODE_I2C_WRITE;
  86         if (algo_data->running) {
  87                 (void) i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
  88                 algo_data->running = false;
  89         }
  90 }
  91
  92 /*
  93  * Write a single byte to the current I2C address, the
  94  * the I2C link must be running or this returns -EIO
  95  */
  96 static int
  97 i2c_algo_dp_aux_put_byte(struct i2c_adapter *adapter, u8 byte)
  98 {
  99         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 100         int ret;
 101
 102         if (!algo_data->running)
 103                 return -EIO;
 104
 105         ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_WRITE, byte, NULL);
 106         return ret;
 107 }
 108
 109 /*
 110  * Read a single byte from the current I2C address, the
 111  * I2C link must be running or this returns -EIO
 112  */
 113 static int
 114 i2c_algo_dp_aux_get_byte(struct i2c_adapter *adapter, u8 *byte_ret)
 115 {
 116         struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
 117         int ret;
 118
 119         if (!algo_data->running)
 120                 return -EIO;
 121
 122         ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_READ, 0, byte_ret);
 123         return ret;
 124 }
 125
 126 static int
 127 i2c_algo_dp_aux_xfer(struct i2c_adapter *adapter,
 128                      struct i2c_msg *msgs,
 129                      int num)
 130 {
 131         int ret = 0;
 132         bool reading = false;
 133         int m;
 134         int b;
 135
 136         for (m = 0; m < num; m++) {
 137                 u16 len = msgs[m].len;
 138                 u8 *buf = msgs[m].buf;
 139                 reading = (msgs[m].flags & I2C_M_RD) != 0;
 140                 ret = i2c_algo_dp_aux_address(adapter, msgs[m].addr, reading);
 141                 if (ret < 0)
 142                         break;
 143                 if (reading) {
 144                         for (b = 0; b < len; b++) {
 145                                 ret = i2c_algo_dp_aux_get_byte(adapter, &buf[b]);
 146                                 if (ret < 0)
 147                                         break;
 148                         }
 149                 } else {
 150                         for (b = 0; b < len; b++) {
 151                                 ret = i2c_algo_dp_aux_put_byte(adapter, buf[b]);
 152                                 if (ret < 0)
 153                                         break;
 154                         }
 155                 }
 156                 if (ret < 0)
 157                         break;
 158         }
 159         if (ret >= 0)
 160                 ret = num;
 161         i2c_algo_dp_aux_stop(adapter, reading);
 162         DRM_DEBUG_KMS("dp_aux_xfer return %d\n", ret);
 163         return ret;
 164 }
 165
 166 static u32
 167 i2c_algo_dp_aux_functionality(struct i2c_adapter *adapter)
 168 {
 169         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 170                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 171                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 172                I2C_FUNC_10BIT_ADDR;
 173 }
 174
 175 static const struct i2c_algorithm i2c_dp_aux_algo = {
 176         .master_xfer    = i2c_algo_dp_aux_xfer,
 177         .functionality  = i2c_algo_dp_aux_functionality,
 178 };
 179
 180 static void
 181 i2c_dp_aux_reset_bus(struct i2c_adapter *adapter)
 182 {
 183         (void) i2c_algo_dp_aux_address(adapter, 0, false);
 184         (void) i2c_algo_dp_aux_stop(adapter, false);
 185
 186 }
 187
 188 static int
 189 i2c_dp_aux_prepare_bus(struct i2c_adapter *adapter)
 190 {
 191         adapter->algo = &i2c_dp_aux_algo;
 192         adapter->retries = 3;
 193         i2c_dp_aux_reset_bus(adapter);
 194         return 0;
 195 }
 196
 197 int
 198 i2c_dp_aux_add_bus(struct i2c_adapter *adapter)
 199 {
 200         int error;
 201
 202         error = i2c_dp_aux_prepare_bus(adapter);
 203         if (error)
 204                 return error;
 205         error = i2c_add_adapter(adapter);
 206         return error;
 207 }
 208 EXPORT_SYMBOL(i2c_dp_aux_add_bus);