diff options
Diffstat (limited to 'drivers/siox/siox-bus-gpio.c')
| -rw-r--r-- | drivers/siox/siox-bus-gpio.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/drivers/siox/siox-bus-gpio.c b/drivers/siox/siox-bus-gpio.c new file mode 100644 index 000000000..aeefeb725 --- /dev/null +++ b/drivers/siox/siox-bus-gpio.c @@ -0,0 +1,174 @@ +// 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/mod_devicetable.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 = dev_err_probe(dev, PTR_ERR(ddata->din), + "Failed to get din GPIO\n"); + goto err; + } + + ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW); + if (IS_ERR(ddata->dout)) { + ret = dev_err_probe(dev, PTR_ERR(ddata->dout), + "Failed to get dout GPIO\n"); + goto err; + } + + ddata->dclk = devm_gpiod_get(dev, "dclk", GPIOD_OUT_LOW); + if (IS_ERR(ddata->dclk)) { + ret = dev_err_probe(dev, PTR_ERR(ddata->dclk), + "Failed to get dclk GPIO\n"); + goto err; + } + + ddata->dld = devm_gpiod_get(dev, "dld", GPIOD_OUT_LOW); + if (IS_ERR(ddata->dld)) { + ret = dev_err_probe(dev, PTR_ERR(ddata->dld), + "Failed to get dld GPIO\n"); + 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_probe(dev, ret, + "Failed to register siox master\n"); +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); |