1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
// SPDX-License-Identifier: GPL-2.0
//
// General Purpose SPI multiplexer
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mux/consumer.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#define SPI_MUX_NO_CS ((unsigned int)-1)
/**
* DOC: Driver description
*
* This driver supports a MUX on an SPI bus. This can be useful when you need
* more chip selects than the hardware peripherals support, or than are
* available in a particular board setup.
*
* The driver will create an additional SPI controller. Devices added under the
* mux will be handled as 'chip selects' on this controller.
*/
/**
* struct spi_mux_priv - the basic spi_mux structure
* @spi: pointer to the device struct attached to the parent
* spi controller
* @current_cs: The current chip select set in the mux
* @child_msg_complete: The mux replaces the complete callback in the child's
* message to its own callback; this field is used by the
* driver to store the child's callback during a transfer
* @child_msg_context: Used to store the child's context to the callback
* @child_msg_dev: Used to store the spi_device pointer to the child
* @mux: mux_control structure used to provide chip selects for
* downstream spi devices
*/
struct spi_mux_priv {
struct spi_device *spi;
unsigned int current_cs;
void (*child_msg_complete)(void *context);
void *child_msg_context;
struct spi_device *child_msg_dev;
struct mux_control *mux;
};
/* should not get called when the parent controller is doing a transfer */
static int spi_mux_select(struct spi_device *spi)
{
struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller);
int ret;
if (priv->current_cs == spi->chip_select)
return 0;
dev_dbg(&priv->spi->dev, "setting up the mux for cs %d\n",
spi->chip_select);
/* copy the child device's settings except for the cs */
priv->spi->max_speed_hz = spi->max_speed_hz;
priv->spi->mode = spi->mode;
priv->spi->bits_per_word = spi->bits_per_word;
ret = mux_control_select(priv->mux, spi->chip_select);
if (ret)
return ret;
priv->current_cs = spi->chip_select;
return 0;
}
static int spi_mux_setup(struct spi_device *spi)
{
struct spi_mux_priv *priv = spi_controller_get_devdata(spi->controller);
/*
* can be called multiple times, won't do a valid setup now but we will
* change the settings when we do a transfer (necessary because we
* can't predict from which device it will be anyway)
*/
return spi_setup(priv->spi);
}
static void spi_mux_complete_cb(void *context)
{
struct spi_mux_priv *priv = (struct spi_mux_priv *)context;
struct spi_controller *ctlr = spi_get_drvdata(priv->spi);
struct spi_message *m = ctlr->cur_msg;
m->complete = priv->child_msg_complete;
m->context = priv->child_msg_context;
m->spi = priv->child_msg_dev;
spi_finalize_current_message(ctlr);
mux_control_deselect(priv->mux);
}
static int spi_mux_transfer_one_message(struct spi_controller *ctlr,
struct spi_message *m)
{
struct spi_mux_priv *priv = spi_controller_get_devdata(ctlr);
struct spi_device *spi = m->spi;
int ret;
ret = spi_mux_select(spi);
if (ret)
return ret;
/*
* Replace the complete callback, context and spi_device with our own
* pointers. Save originals
*/
priv->child_msg_complete = m->complete;
priv->child_msg_context = m->context;
priv->child_msg_dev = m->spi;
m->complete = spi_mux_complete_cb;
m->context = priv;
m->spi = priv->spi;
/* do the transfer */
return spi_async(priv->spi, m);
}
static int spi_mux_probe(struct spi_device *spi)
{
struct spi_controller *ctlr;
struct spi_mux_priv *priv;
int ret;
ctlr = spi_alloc_master(&spi->dev, sizeof(*priv));
if (!ctlr)
return -ENOMEM;
spi_set_drvdata(spi, ctlr);
priv = spi_controller_get_devdata(ctlr);
priv->spi = spi;
priv->mux = devm_mux_control_get(&spi->dev, NULL);
if (IS_ERR(priv->mux)) {
ret = PTR_ERR(priv->mux);
if (ret != -EPROBE_DEFER)
dev_err(&spi->dev, "failed to get control-mux\n");
goto err_put_ctlr;
}
priv->current_cs = SPI_MUX_NO_CS;
/* supported modes are the same as our parent's */
ctlr->mode_bits = spi->controller->mode_bits;
ctlr->flags = spi->controller->flags;
ctlr->transfer_one_message = spi_mux_transfer_one_message;
ctlr->setup = spi_mux_setup;
ctlr->num_chipselect = mux_control_states(priv->mux);
ctlr->bus_num = -1;
ctlr->dev.of_node = spi->dev.of_node;
ret = devm_spi_register_controller(&spi->dev, ctlr);
if (ret)
goto err_put_ctlr;
return 0;
err_put_ctlr:
spi_controller_put(ctlr);
return ret;
}
static const struct of_device_id spi_mux_of_match[] = {
{ .compatible = "spi-mux" },
{ }
};
static struct spi_driver spi_mux_driver = {
.probe = spi_mux_probe,
.driver = {
.name = "spi-mux",
.of_match_table = spi_mux_of_match,
},
};
module_spi_driver(spi_mux_driver);
MODULE_DESCRIPTION("SPI multiplexer");
MODULE_LICENSE("GPL");
|
