siox-bus-gpio.c

  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(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 -ENOMEM;
 97
 98	platform_set_drvdata(pdev, smaster);
 99	ddata = siox_master_get_devdata(smaster);
100
101	ddata->din = devm_gpiod_get(dev, "din", GPIOD_IN);
102	if (IS_ERR(ddata->din))
103		return dev_err_probe(dev, PTR_ERR(ddata->din),
104				     "Failed to get din GPIO\n");
105
106	ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW);
107	if (IS_ERR(ddata->dout))
108		return dev_err_probe(dev, PTR_ERR(ddata->dout),
109				     "Failed to get dout GPIO\n");
110
111	ddata->dclk = devm_gpiod_get(dev, "dclk", GPIOD_OUT_LOW);
112	if (IS_ERR(ddata->dclk))
113		return dev_err_probe(dev, PTR_ERR(ddata->dclk),
114				     "Failed to get dclk GPIO\n");
115
116	ddata->dld = devm_gpiod_get(dev, "dld", GPIOD_OUT_LOW);
117	if (IS_ERR(ddata->dld))
118		return dev_err_probe(dev, PTR_ERR(ddata->dld),
119				     "Failed to get dld GPIO\n");
120
121	smaster->pushpull = siox_gpio_pushpull;
122	/* XXX: determine automatically like spi does */
123	smaster->busno = 0;
124
125	ret = devm_siox_master_register(dev, smaster);
126	if (ret)
127		return dev_err_probe(dev, ret,
128				     "Failed to register siox master\n");
129
130	return 0;
131}
132
133static const struct of_device_id siox_gpio_dt_ids[] = {
134	{ .compatible = "eckelmann,siox-gpio", },
135	{ /* sentinel */ }
136};
137MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);
138
139static struct platform_driver siox_gpio_driver = {
140	.probe = siox_gpio_probe,
141
142	.driver = {
143		.name = DRIVER_NAME,
144		.of_match_table = siox_gpio_dt_ids,
145	},
146};
147module_platform_driver(siox_gpio_driver);
148
149MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
150MODULE_DESCRIPTION("SIOX GPIO bus driver");
151MODULE_LICENSE("GPL v2");
152MODULE_ALIAS("platform:" DRIVER_NAME);