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 = siox_master_alloc(&pdev->dev, 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, smaster);
101 	ddata = siox_master_get_devdata(smaster);
102 
103 	ddata->din = devm_gpiod_get(dev, "din", GPIOD_IN);
104 	if (IS_ERR(ddata->din)) {
105 		ret = PTR_ERR(ddata->din);
106 		dev_err(dev, "Failed to get %s GPIO: %d\n", "din", ret);
107 		goto err;
108 	}
109 
110 	ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW);
111 	if (IS_ERR(ddata->dout)) {
112 		ret = PTR_ERR(ddata->dout);
113 		dev_err(dev, "Failed to get %s GPIO: %d\n", "dout", ret);
114 		goto err;
115 	}
116 
117 	ddata->dclk = devm_gpiod_get(dev, "dclk", GPIOD_OUT_LOW);
118 	if (IS_ERR(ddata->dclk)) {
119 		ret = PTR_ERR(ddata->dclk);
120 		dev_err(dev, "Failed to get %s GPIO: %d\n", "dclk", ret);
121 		goto err;
122 	}
123 
124 	ddata->dld = devm_gpiod_get(dev, "dld", GPIOD_OUT_LOW);
125 	if (IS_ERR(ddata->dld)) {
126 		ret = PTR_ERR(ddata->dld);
127 		dev_err(dev, "Failed to get %s GPIO: %d\n", "dld", ret);
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(dev, "Failed to register siox master: %d\n", ret);
138 err:
139 		siox_master_put(smaster);
140 	}
141 
142 	return ret;
143 }
144 
siox_gpio_remove(struct platform_device * pdev)145 static int siox_gpio_remove(struct platform_device *pdev)
146 {
147 	struct siox_master *master = platform_get_drvdata(pdev);
148 
149 	siox_master_unregister(master);
150 
151 	return 0;
152 }
153 
154 static const struct of_device_id siox_gpio_dt_ids[] = {
155 	{ .compatible = "eckelmann,siox-gpio", },
156 	{ /* sentinel */ }
157 };
158 MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);
159 
160 static struct platform_driver siox_gpio_driver = {
161 	.probe = siox_gpio_probe,
162 	.remove = siox_gpio_remove,
163 
164 	.driver = {
165 		.name = DRIVER_NAME,
166 		.of_match_table = siox_gpio_dt_ids,
167 	},
168 };
169 module_platform_driver(siox_gpio_driver);
170 
171 MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
172 MODULE_LICENSE("GPL v2");
173 MODULE_ALIAS("platform:" DRIVER_NAME);
174