1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015-2017 Pengutronix, Uwe Kleine-K��nig <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(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
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 = 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
134static const struct of_device_id siox_gpio_dt_ids[] = {
135	{ .compatible = "eckelmann,siox-gpio", },
136	{ /* sentinel */ }
137};
138MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);
139
140static 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};
148module_platform_driver(siox_gpio_driver);
149
150MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
151MODULE_LICENSE("GPL v2");
152MODULE_ALIAS("platform:" DRIVER_NAME);
153