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