Root/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 */
34static int
35i2c_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 */
55static int
56i2c_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 */
76static void
77i2c_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 */
96static int
97i2c_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 */
113static int
114i2c_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
126static int
127i2c_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
166static u32
167i2c_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
175static 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
180static void
181i2c_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
188static int
189i2c_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
197int
198i2c_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}
208EXPORT_SYMBOL(i2c_dp_aux_add_bus);
209

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