[PATCH RFC v3 2/4] siox: add gpio bus driver

[Uwe Kleine-KÃnig]

Add a driver to create a SIOX master from four GPIOs.

Signed-off-by: Uwe Kleine-KÃnig <u.kleine-koenig@xxxxxxxxxxxxxx>
---
 drivers/siox/Kconfig         |   7 ++
 drivers/siox/Makefile        |   1 +
 drivers/siox/siox-bus-gpio.c | 175 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 183 insertions(+)
 create mode 100644 drivers/siox/siox-bus-gpio.c

diff --git a/drivers/siox/Kconfig b/drivers/siox/Kconfig
index 471fbc009521..7bd28527203f 100644
--- a/drivers/siox/Kconfig
+++ b/drivers/siox/Kconfig
@@ -1,2 +1,9 @@
 menuconfig SIOX
 	tristate "Eckelmann SIOX Support"
+
+if SIOX
+
+config SIOX_BUS_GPIO
+	tristate "SIOX GPIO bus driver"
+
+endif
diff --git a/drivers/siox/Makefile b/drivers/siox/Makefile
index d55cb5e08868..a956f65206d5 100644
--- a/drivers/siox/Makefile
+++ b/drivers/siox/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_SIOX) += siox-core.o
+obj-$(CONFIG_SIOX_BUS_GPIO) += siox-bus-gpio.o
diff --git a/drivers/siox/siox-bus-gpio.c b/drivers/siox/siox-bus-gpio.c
new file mode 100644
index 000000000000..6ac4b70a4362
--- /dev/null
+++ b/drivers/siox/siox-bus-gpio.c
@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2015 Pengutronix, Uwe Kleine-KÃnig <kernel@xxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License version 2 as published by the
+ * Free Software Foundation.
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <linux/delay.h>
+
+#include "siox.h"
+
+#define DRIVER_NAME "siox-gpio"
+
+struct siox_gpio_ddata {
+	struct gpio_desc *din;
+	struct gpio_desc *dout;
+	struct gpio_desc *dclk;
+	struct gpio_desc *dld;
+};
+
+unsigned int siox_clkhigh_ns = 1000;
+unsigned int siox_loadhigh_ns;
+unsigned int siox_bytegap_ns;
+
+static int siox_gpio_pushpull(struct siox_master *smaster,
+			      size_t setbuf_len, const u8 setbuf[],
+			      size_t getbuf_len, u8 getbuf[])
+{
+	struct siox_gpio_ddata *ddata = siox_master_get_devdata(smaster);
+	size_t i;
+	size_t cycles = max(setbuf_len, getbuf_len);
+
+	/* reset data and clock */
+	gpiod_set_value_cansleep(ddata->dout, 0);
+	gpiod_set_value_cansleep(ddata->dclk, 0);
+
+	gpiod_set_value_cansleep(ddata->dld, 1);
+	ndelay(siox_loadhigh_ns);
+	gpiod_set_value_cansleep(ddata->dld, 0);
+
+	for (i = 0; i < cycles; ++i) {
+		u8 set = 0, get = 0;
+		size_t j;
+
+		if (i >= cycles - setbuf_len)
+			set = setbuf[i - (cycles - setbuf_len)];
+
+		for (j = 0; j < 8; ++j) {
+			get <<= 1;
+			if (gpiod_get_value_cansleep(ddata->din))
+				get |= 1;
+
+			/* DOUT is logically inverted */
+			gpiod_set_value_cansleep(ddata->dout, !(set & 0x80));
+			set <<= 1;
+
+			gpiod_set_value_cansleep(ddata->dclk, 1);
+			ndelay(siox_clkhigh_ns);
+			gpiod_set_value_cansleep(ddata->dclk, 0);
+		}
+
+		if (i < getbuf_len)
+			getbuf[i] = get;
+
+		ndelay(siox_bytegap_ns);
+	}
+
+	gpiod_set_value_cansleep(ddata->dld, 1);
+	ndelay(siox_loadhigh_ns);
+	gpiod_set_value_cansleep(ddata->dld, 0);
+
+	/*
+	 * Resetting dout isn't necessary protocol wise, but it makes the
+	 * signals more pretty because the dout level is deterministic between
+	 * cycles. Note that this only affects dout between the master and the
+	 * first siox device. dout for the later devices depend on the output of
+	 * the previous siox device.
+	 */
+	gpiod_set_value_cansleep(ddata->dout, 0);
+
+	return 0;
+}
+
+static int siox_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct siox_gpio_ddata *ddata;
+	int ret;
+	struct siox_master *smaster;
+
+	smaster = siox_master_alloc(&pdev->dev, sizeof(*ddata));
+	if (!smaster) {
+		dev_err(dev, "failed to allocate siox master\n");
+		return -ENOMEM;
+	}
+
+	platform_set_drvdata(pdev, smaster);
+	ddata = siox_master_get_devdata(smaster);
+
+	ddata->din = devm_gpiod_get(dev, "din", GPIOD_IN);
+	if (IS_ERR(ddata->din)) {
+		ret = PTR_ERR(ddata->din);
+		dev_err(dev, "Failed to get %s GPIO: %d\n", "din", ret);
+		goto err;
+	}
+
+	ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW);
+	if (IS_ERR(ddata->dout)) {
+		ret = PTR_ERR(ddata->dout);
+		dev_err(dev, "Failed to get %s GPIO: %d\n", "dout", ret);
+		goto err;
+	}
+
+	ddata->dclk = devm_gpiod_get(dev, "dclk", GPIOD_OUT_LOW);
+	if (IS_ERR(ddata->dclk)) {
+		ret = PTR_ERR(ddata->dclk);
+		dev_err(dev, "Failed to get %s GPIO: %d\n", "dclk", ret);
+		goto err;
+	}
+
+	ddata->dld = devm_gpiod_get(dev, "dld", GPIOD_OUT_LOW);
+	if (IS_ERR(ddata->dld)) {
+		ret = PTR_ERR(ddata->dld);
+		dev_err(dev, "Failed to get %s GPIO: %d\n", "dld", ret);
+		goto err;
+	}
+
+	smaster->pushpull = siox_gpio_pushpull;
+	/* XXX: determine automatically like spi does */
+	smaster->busno = 0;
+
+	ret = siox_master_register(smaster);
+	if (ret) {
+		dev_err(dev, "Failed to register siox master: %d\n", ret);
+err:
+		siox_master_put(smaster);
+	}
+
+	return ret;
+}
+
+static int siox_gpio_remove(struct platform_device *pdev)
+{
+	struct siox_master *master = platform_get_drvdata(pdev);
+
+	siox_master_unregister(master);
+
+	return 0;
+}
+
+static const struct of_device_id siox_gpio_dt_ids[] = {
+	{ .compatible = "eckelmann,siox-gpio", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);
+
+static struct platform_driver siox_gpio_driver = {
+	.probe = siox_gpio_probe,
+	.remove = siox_gpio_remove,
+
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = siox_gpio_dt_ids,
+	},
+};
+module_platform_driver(siox_gpio_driver);
+
+MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@xxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRIVER_NAME);
-- 
2.8.0.rc3