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);