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
17 struct 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
24 static unsigned int siox_clkhigh_ns = 1000;
25 static unsigned int siox_loadhigh_ns;
26 static unsigned int siox_bytegap_ns;
27
siox_gpio_pushpull(struct siox_master * smaster,size_t setbuf_len,const u8 setbuf[],size_t getbuf_len,u8 getbuf[])28 static 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(ddata->dout, 0);
38 gpiod_set_value_cansleep(ddata->dclk, 0);
39
40 gpiod_set_value_cansleep(ddata->dld, 1);
41 ndelay(siox_loadhigh_ns);
42 gpiod_set_value_cansleep(ddata->dld, 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(ddata->din))
54 get |= 1;
55
56 /* DOUT is logically inverted */
57 gpiod_set_value_cansleep(ddata->dout, !(set & 0x80));
58 set <<= 1;
59
60 gpiod_set_value_cansleep(ddata->dclk, 1);
61 ndelay(siox_clkhigh_ns);
62 gpiod_set_value_cansleep(ddata->dclk, 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(ddata->dld, 1);
72 ndelay(siox_loadhigh_ns);
73 gpiod_set_value_cansleep(ddata->dld, 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(ddata->dout, 0);
83
84 return 0;
85 }
86
siox_gpio_probe(struct platform_device * pdev)87 static 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 = devm_siox_master_alloc(dev, sizeof(*ddata));
95 if (!smaster)
96 return dev_err_probe(dev, -ENOMEM,
97 "failed to allocate siox master\n");
98
99 platform_set_drvdata(pdev, smaster);
100 ddata = siox_master_get_devdata(smaster);
101
102 ddata->din = devm_gpiod_get(dev, "din", GPIOD_IN);
103 if (IS_ERR(ddata->din))
104 return dev_err_probe(dev, PTR_ERR(ddata->din),
105 "Failed to get din GPIO\n");
106
107 ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW);
108 if (IS_ERR(ddata->dout))
109 return dev_err_probe(dev, PTR_ERR(ddata->dout),
110 "Failed to get dout GPIO\n");
111
112 ddata->dclk = devm_gpiod_get(dev, "dclk", GPIOD_OUT_LOW);
113 if (IS_ERR(ddata->dclk))
114 return dev_err_probe(dev, PTR_ERR(ddata->dclk),
115 "Failed to get dclk GPIO\n");
116
117 ddata->dld = devm_gpiod_get(dev, "dld", GPIOD_OUT_LOW);
118 if (IS_ERR(ddata->dld))
119 return dev_err_probe(dev, PTR_ERR(ddata->dld),
120 "Failed to get dld GPIO\n");
121
122 smaster->pushpull = siox_gpio_pushpull;
123 /* XXX: determine automatically like spi does */
124 smaster->busno = 0;
125
126 ret = devm_siox_master_register(dev, smaster);
127 if (ret)
128 return dev_err_probe(dev, ret,
129 "Failed to register siox master\n");
130
131 return 0;
132 }
133
134 static const struct of_device_id siox_gpio_dt_ids[] = {
135 { .compatible = "eckelmann,siox-gpio", },
136 { /* sentinel */ }
137 };
138 MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);
139
140 static struct platform_driver siox_gpio_driver = {
141 .probe = siox_gpio_probe,
142
143 .driver = {
144 .name = DRIVER_NAME,
145 .of_match_table = siox_gpio_dt_ids,
146 },
147 };
148 module_platform_driver(siox_gpio_driver);
149
150 MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
151 MODULE_DESCRIPTION("SIOX GPIO bus driver");
152 MODULE_LICENSE("GPL v2");
153 MODULE_ALIAS("platform:" DRIVER_NAME);
154