1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015-2017 Pengutronix, Uwe Kleine-König <kernel@pengutronix.de>
4 */
5
6#include <linux/gpio/consumer.h>
7#include <linux/module.h>
8#include <linux/mod_devicetable.h>
9#include <linux/platform_device.h>
10
11#include <linux/delay.h>
12
13#include "siox.h"
14
15#define DRIVER_NAME "siox-gpio"
16
17struct siox_gpio_ddata {
18 struct gpio_desc *din;
19 struct gpio_desc *dout;
20 struct gpio_desc *dclk;
21 struct gpio_desc *dld;
22};
23
24static unsigned int siox_clkhigh_ns = 1000;
25static unsigned int siox_loadhigh_ns;
26static unsigned int siox_bytegap_ns;
27
28static int siox_gpio_pushpull(struct siox_master *smaster,
29 size_t setbuf_len, const u8 setbuf[],
30 size_t getbuf_len, u8 getbuf[])
31{
32 struct siox_gpio_ddata *ddata = siox_master_get_devdata(smaster);
33 size_t i;
34 size_t cycles = max(setbuf_len, getbuf_len);
35
36 /* reset data and clock */
37 gpiod_set_value_cansleep(desc: ddata->dout, value: 0);
38 gpiod_set_value_cansleep(desc: ddata->dclk, value: 0);
39
40 gpiod_set_value_cansleep(desc: ddata->dld, value: 1);
41 ndelay(siox_loadhigh_ns);
42 gpiod_set_value_cansleep(desc: ddata->dld, value: 0);
43
44 for (i = 0; i < cycles; ++i) {
45 u8 set = 0, get = 0;
46 size_t j;
47
48 if (i >= cycles - setbuf_len)
49 set = setbuf[i - (cycles - setbuf_len)];
50
51 for (j = 0; j < 8; ++j) {
52 get <<= 1;
53 if (gpiod_get_value_cansleep(desc: ddata->din))
54 get |= 1;
55
56 /* DOUT is logically inverted */
57 gpiod_set_value_cansleep(desc: ddata->dout, value: !(set & 0x80));
58 set <<= 1;
59
60 gpiod_set_value_cansleep(desc: ddata->dclk, value: 1);
61 ndelay(siox_clkhigh_ns);
62 gpiod_set_value_cansleep(desc: ddata->dclk, value: 0);
63 }
64
65 if (i < getbuf_len)
66 getbuf[i] = get;
67
68 ndelay(siox_bytegap_ns);
69 }
70
71 gpiod_set_value_cansleep(desc: ddata->dld, value: 1);
72 ndelay(siox_loadhigh_ns);
73 gpiod_set_value_cansleep(desc: ddata->dld, value: 0);
74
75 /*
76 * Resetting dout isn't necessary protocol wise, but it makes the
77 * signals more pretty because the dout level is deterministic between
78 * cycles. Note that this only affects dout between the master and the
79 * first siox device. dout for the later devices depend on the output of
80 * the previous siox device.
81 */
82 gpiod_set_value_cansleep(desc: ddata->dout, value: 0);
83
84 return 0;
85}
86
87static int siox_gpio_probe(struct platform_device *pdev)
88{
89 struct device *dev = &pdev->dev;
90 struct siox_gpio_ddata *ddata;
91 int ret;
92 struct siox_master *smaster;
93
94 smaster = siox_master_alloc(dev: &pdev->dev, size: sizeof(*ddata));
95 if (!smaster) {
96 dev_err(dev, "failed to allocate siox master\n");
97 return -ENOMEM;
98 }
99
100 platform_set_drvdata(pdev, data: smaster);
101 ddata = siox_master_get_devdata(smaster);
102
103 ddata->din = devm_gpiod_get(dev, con_id: "din", flags: GPIOD_IN);
104 if (IS_ERR(ptr: ddata->din)) {
105 ret = dev_err_probe(dev, err: PTR_ERR(ptr: ddata->din),
106 fmt: "Failed to get din GPIO\n");
107 goto err;
108 }
109
110 ddata->dout = devm_gpiod_get(dev, con_id: "dout", flags: GPIOD_OUT_LOW);
111 if (IS_ERR(ptr: ddata->dout)) {
112 ret = dev_err_probe(dev, err: PTR_ERR(ptr: ddata->dout),
113 fmt: "Failed to get dout GPIO\n");
114 goto err;
115 }
116
117 ddata->dclk = devm_gpiod_get(dev, con_id: "dclk", flags: GPIOD_OUT_LOW);
118 if (IS_ERR(ptr: ddata->dclk)) {
119 ret = dev_err_probe(dev, err: PTR_ERR(ptr: ddata->dclk),
120 fmt: "Failed to get dclk GPIO\n");
121 goto err;
122 }
123
124 ddata->dld = devm_gpiod_get(dev, con_id: "dld", flags: GPIOD_OUT_LOW);
125 if (IS_ERR(ptr: ddata->dld)) {
126 ret = dev_err_probe(dev, err: PTR_ERR(ptr: ddata->dld),
127 fmt: "Failed to get dld GPIO\n");
128 goto err;
129 }
130
131 smaster->pushpull = siox_gpio_pushpull;
132 /* XXX: determine automatically like spi does */
133 smaster->busno = 0;
134
135 ret = siox_master_register(smaster);
136 if (ret) {
137 dev_err_probe(dev, err: ret,
138 fmt: "Failed to register siox master\n");
139err:
140 siox_master_put(smaster);
141 }
142
143 return ret;
144}
145
146static int siox_gpio_remove(struct platform_device *pdev)
147{
148 struct siox_master *master = platform_get_drvdata(pdev);
149
150 siox_master_unregister(smaster: master);
151
152 return 0;
153}
154
155static const struct of_device_id siox_gpio_dt_ids[] = {
156 { .compatible = "eckelmann,siox-gpio", },
157 { /* sentinel */ }
158};
159MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);
160
161static struct platform_driver siox_gpio_driver = {
162 .probe = siox_gpio_probe,
163 .remove = siox_gpio_remove,
164
165 .driver = {
166 .name = DRIVER_NAME,
167 .of_match_table = siox_gpio_dt_ids,
168 },
169};
170module_platform_driver(siox_gpio_driver);
171
172MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
173MODULE_LICENSE("GPL v2");
174MODULE_ALIAS("platform:" DRIVER_NAME);
175

source code of linux/drivers/siox/siox-bus-gpio.c