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Commit fd639726 authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Greg Kroah-Hartman
Browse files

siox: add gpio bus driver 



This bus driver uses GPIOs to control the four SIOX bus lines.

Acked-by: default avatarGavin Schenk <g.schenk@eckelmann.de>
Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 297a344d

Documentation/devicetree/bindings/siox/eckelmann,siox-gpio.txt

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Eckelmann SIOX GPIO bus



Required properties:

- compatible : "eckelmann,siox-gpio"

- din-gpios, dout-gpios, dclk-gpios, dld-gpios: references gpios for the

    corresponding bus signals.



Examples:



        siox {

                compatible = "eckelmann,siox-gpio";

                pinctrl-names = "default";

                pinctrl-0 = <&pinctrl_siox>;



                din-gpios = <&gpio6 11 0>;

                dout-gpios = <&gpio6 8 0>;

                dclk-gpios = <&gpio6 9 0>;

                dld-gpios = <&gpio6 10 0>;

        };

Documentation/devicetree/bindings/vendor-prefixes.txt

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@@ -97,6 +97,7 @@ dptechnics DPTechnics 
dragino	Dragino Technology Co., Limited

ea	Embedded Artists AB

ebv	EBV Elektronik

eckelmann	Eckelmann AG

edt	Emerging Display Technologies

eeti	eGalax_eMPIA Technology Inc

elan	Elan Microelectronic Corp.

drivers/siox/Kconfig

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@@ -7,3 +7,12 @@ menuconfig SIOX 
	  to drive additional I/O units.



	  Unless you know better, it is probably safe to say "no" here.



if SIOX



config SIOX_BUS_GPIO

	tristate "SIOX GPIO bus driver"

	help

	  SIOX bus driver that controls the four bus lines using GPIOs.



endif

drivers/siox/Makefile

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obj-$(CONFIG_SIOX) += siox-core.o

obj-$(CONFIG_SIOX_BUS_GPIO) += siox-bus-gpio.o

drivers/siox/siox-bus-gpio.c

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// SPDX-License-Identifier: GPL-2.0

/*

 * Copyright (C) 2015-2017 Pengutronix, Uwe Kleine-König <kernel@pengutronix.de>

 */



#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;

};



static unsigned int siox_clkhigh_ns = 1000;

static unsigned int siox_loadhigh_ns;

static 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@pengutronix.de>");

MODULE_LICENSE("GPL v2");

MODULE_ALIAS("platform:" DRIVER_NAME);