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Uwe Kleine-Königgregkh
Uwe Kleine-König
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gregkh
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siox: add gpio bus driver
This bus driver uses GPIOs to control the four SIOX bus lines. Acked-by: Gavin Schenk <g.schenk@eckelmann.de> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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‎Documentation/devicetree/bindings/siox/eckelmann,siox-gpio.txt‎

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Eckelmann SIOX GPIO bus
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Required properties:
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- compatible : "eckelmann,siox-gpio"
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- din-gpios, dout-gpios, dclk-gpios, dld-gpios: references gpios for the
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corresponding bus signals.
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Examples:
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siox {
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compatible = "eckelmann,siox-gpio";
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pinctrl-names = "default";
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pinctrl-0 = <&pinctrl_siox>;
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din-gpios = <&gpio6 11 0>;
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dout-gpios = <&gpio6 8 0>;
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dclk-gpios = <&gpio6 9 0>;
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dld-gpios = <&gpio6 10 0>;
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};

‎Documentation/devicetree/bindings/vendor-prefixes.txt‎

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@@ -97,6 +97,7 @@ dptechnics DPTechnics
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dragino Dragino Technology Co., Limited
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ea Embedded Artists AB
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ebv EBV Elektronik
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eckelmann Eckelmann AG
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edt Emerging Display Technologies
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eeti eGalax_eMPIA Technology Inc
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elan Elan Microelectronic Corp.

‎drivers/siox/Kconfig‎

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@@ -7,3 +7,12 @@ menuconfig SIOX
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to drive additional I/O units.
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Unless you know better, it is probably safe to say "no" here.
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if SIOX
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config SIOX_BUS_GPIO
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tristate "SIOX GPIO bus driver"
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help
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SIOX bus driver that controls the four bus lines using GPIOs.
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endif

‎drivers/siox/Makefile‎

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

‎drivers/siox/siox-bus-gpio.c‎

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2015-2017 Pengutronix, Uwe Kleine-König <kernel@pengutronix.de>
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*/
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#include <linux/gpio/consumer.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/delay.h>
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#include "siox.h"
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#define DRIVER_NAME "siox-gpio"
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struct siox_gpio_ddata {
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struct gpio_desc *din;
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struct gpio_desc *dout;
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struct gpio_desc *dclk;
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struct gpio_desc *dld;
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};
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static unsigned int siox_clkhigh_ns = 1000;
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static unsigned int siox_loadhigh_ns;
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static unsigned int siox_bytegap_ns;
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static int siox_gpio_pushpull(struct siox_master *smaster,
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size_t setbuf_len, const u8 setbuf[],
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size_t getbuf_len, u8 getbuf[])
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{
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struct siox_gpio_ddata *ddata = siox_master_get_devdata(smaster);
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size_t i;
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size_t cycles = max(setbuf_len, getbuf_len);
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/* reset data and clock */
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gpiod_set_value_cansleep(ddata->dout, 0);
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gpiod_set_value_cansleep(ddata->dclk, 0);
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gpiod_set_value_cansleep(ddata->dld, 1);
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ndelay(siox_loadhigh_ns);
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gpiod_set_value_cansleep(ddata->dld, 0);
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for (i = 0; i < cycles; ++i) {
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u8 set = 0, get = 0;
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size_t j;
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if (i >= cycles - setbuf_len)
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set = setbuf[i - (cycles - setbuf_len)];
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for (j = 0; j < 8; ++j) {
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get <<= 1;
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if (gpiod_get_value_cansleep(ddata->din))
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get |= 1;
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/* DOUT is logically inverted */
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gpiod_set_value_cansleep(ddata->dout, !(set & 0x80));
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set <<= 1;
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gpiod_set_value_cansleep(ddata->dclk, 1);
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ndelay(siox_clkhigh_ns);
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gpiod_set_value_cansleep(ddata->dclk, 0);
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}
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if (i < getbuf_len)
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getbuf[i] = get;
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ndelay(siox_bytegap_ns);
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}
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gpiod_set_value_cansleep(ddata->dld, 1);
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ndelay(siox_loadhigh_ns);
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gpiod_set_value_cansleep(ddata->dld, 0);
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/*
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* Resetting dout isn't necessary protocol wise, but it makes the
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* signals more pretty because the dout level is deterministic between
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* cycles. Note that this only affects dout between the master and the
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* first siox device. dout for the later devices depend on the output of
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* the previous siox device.
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*/
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gpiod_set_value_cansleep(ddata->dout, 0);
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return 0;
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}
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static int siox_gpio_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct siox_gpio_ddata *ddata;
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int ret;
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struct siox_master *smaster;
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smaster = siox_master_alloc(&pdev->dev, sizeof(*ddata));
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if (!smaster) {
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dev_err(dev, "failed to allocate siox master\n");
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return -ENOMEM;
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}
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platform_set_drvdata(pdev, smaster);
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ddata = siox_master_get_devdata(smaster);
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ddata->din = devm_gpiod_get(dev, "din", GPIOD_IN);
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if (IS_ERR(ddata->din)) {
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ret = PTR_ERR(ddata->din);
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dev_err(dev, "Failed to get %s GPIO: %d\n", "din", ret);
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goto err;
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}
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ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW);
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if (IS_ERR(ddata->dout)) {
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ret = PTR_ERR(ddata->dout);
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dev_err(dev, "Failed to get %s GPIO: %d\n", "dout", ret);
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goto err;
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}
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ddata->dclk = devm_gpiod_get(dev, "dclk", GPIOD_OUT_LOW);
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if (IS_ERR(ddata->dclk)) {
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ret = PTR_ERR(ddata->dclk);
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dev_err(dev, "Failed to get %s GPIO: %d\n", "dclk", ret);
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goto err;
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}
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ddata->dld = devm_gpiod_get(dev, "dld", GPIOD_OUT_LOW);
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if (IS_ERR(ddata->dld)) {
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ret = PTR_ERR(ddata->dld);
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dev_err(dev, "Failed to get %s GPIO: %d\n", "dld", ret);
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goto err;
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}
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smaster->pushpull = siox_gpio_pushpull;
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/* XXX: determine automatically like spi does */
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smaster->busno = 0;
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ret = siox_master_register(smaster);
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if (ret) {
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dev_err(dev, "Failed to register siox master: %d\n", ret);
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err:
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siox_master_put(smaster);
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}
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return ret;
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}
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static int siox_gpio_remove(struct platform_device *pdev)
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{
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struct siox_master *master = platform_get_drvdata(pdev);
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siox_master_unregister(master);
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return 0;
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}
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static const struct of_device_id siox_gpio_dt_ids[] = {
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{ .compatible = "eckelmann,siox-gpio", },
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{ /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);
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static struct platform_driver siox_gpio_driver = {
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.probe = siox_gpio_probe,
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.remove = siox_gpio_remove,
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.driver = {
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.name = DRIVER_NAME,
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.of_match_table = siox_gpio_dt_ids,
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},
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};
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module_platform_driver(siox_gpio_driver);
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MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
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MODULE_LICENSE("GPL v2");
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MODULE_ALIAS("platform:" DRIVER_NAME);

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