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>

5 files changed, 202 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/siox/eckelmann,siox-gpio.txt b/Documentation/devicetree/bindings/siox/eckelmann,siox-gpio.txt
new file mode 100644
index 000000000000..55259cf39c25
--- /dev/null
+++ b/Documentation/devicetree/bindings/siox/eckelmann,siox-gpio.txt
@@ -0,0 +1,19 @@
+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>;
+        };
diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
index 0994bdd82cd3..889d1c0f5050 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.txt
+++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
@@ -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.
diff --git a/drivers/siox/Kconfig b/drivers/siox/Kconfig
index bd24d9b50dc6..083d2e62189a 100644
--- a/drivers/siox/Kconfig
+++ b/drivers/siox/Kconfig
@@ -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
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..ea7ef982968b
--- /dev/null
+++ b/drivers/siox/siox-bus-gpio.c
@@ -0,0 +1,172 @@
+// 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);