bus: add driver for the Technologic Systems NBUS (5b143d2a) · Commits · e / devices / android_kernel_fairphone_FP5

drivers/bus/Kconfig

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		@@ -157,6 +157,14 @@ config TEGRA_GMI
		Driver for the Tegra Generic Memory Interface bus which can be used
		to attach devices such as NOR, UART, FPGA and more.

		config TS_NBUS
		tristate "Technologic Systems NBUS Driver"
		depends on SOC_IMX28
		depends on OF_GPIO && PWM
		help
		Driver for the Technologic Systems NBUS which is used to interface
		with the peripherals in the FPGA of the TS-4600 SoM.

		config UNIPHIER_SYSTEM_BUS
		tristate "UniPhier System Bus driver"
		depends on ARCH_UNIPHIER && OF

drivers/bus/Makefile

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		@@ -20,6 +20,7 @@ obj-$(CONFIG_SUNXI_RSB) += sunxi-rsb.o
		obj-$(CONFIG_SIMPLE_PM_BUS) += simple-pm-bus.o
		obj-$(CONFIG_TEGRA_ACONNECT) += tegra-aconnect.o
		obj-$(CONFIG_TEGRA_GMI) += tegra-gmi.o
		obj-$(CONFIG_TS_NBUS) += ts-nbus.o
		obj-$(CONFIG_UNIPHIER_SYSTEM_BUS) += uniphier-system-bus.o
		obj-$(CONFIG_VEXPRESS_CONFIG) += vexpress-config.o

drivers/bus/ts-nbus.c

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		/*
		* NBUS driver for TS-4600 based boards
		*
		* Copyright (c) 2016 - Savoir-faire Linux
		* Author: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
		*
		* This file is licensed under the terms of the GNU General Public
		* License version 2. This program is licensed "as is" without any
		* warranty of any kind, whether express or implied.
		*
		* This driver implements a GPIOs bit-banged bus, called the NBUS by Technologic
		* Systems. It is used to communicate with the peripherals in the FPGA on the
		* TS-4600 SoM.
		*/

		#include <linux/bitops.h>
		#include <linux/gpio/consumer.h>
		#include <linux/kernel.h>
		#include <linux/module.h>
		#include <linux/mutex.h>
		#include <linux/of_platform.h>
		#include <linux/platform_device.h>
		#include <linux/pwm.h>
		#include <linux/ts-nbus.h>

		#define TS_NBUS_DIRECTION_IN 0
		#define TS_NBUS_DIRECTION_OUT 1
		#define TS_NBUS_WRITE_ADR 0
		#define TS_NBUS_WRITE_VAL 1

		struct ts_nbus {
		struct pwm_device *pwm;
		struct gpio_descs *data;
		struct gpio_desc *csn;
		struct gpio_desc *txrx;
		struct gpio_desc *strobe;
		struct gpio_desc *ale;
		struct gpio_desc *rdy;
		struct mutex lock;
		};

		/*
		* request all gpios required by the bus.
		*/
		static int ts_nbus_init_pdata(struct platform_device *pdev, struct ts_nbus
		*ts_nbus)
		{
		ts_nbus->data = devm_gpiod_get_array(&pdev->dev, "ts,data",
		GPIOD_OUT_HIGH);
		if (IS_ERR(ts_nbus->data)) {
		dev_err(&pdev->dev, "failed to retrieve ts,data-gpio from dts\n");
		return PTR_ERR(ts_nbus->data);
		}

		ts_nbus->csn = devm_gpiod_get(&pdev->dev, "ts,csn", GPIOD_OUT_HIGH);
		if (IS_ERR(ts_nbus->csn)) {
		dev_err(&pdev->dev, "failed to retrieve ts,csn-gpio from dts\n");
		return PTR_ERR(ts_nbus->csn);
		}

		ts_nbus->txrx = devm_gpiod_get(&pdev->dev, "ts,txrx", GPIOD_OUT_HIGH);
		if (IS_ERR(ts_nbus->txrx)) {
		dev_err(&pdev->dev, "failed to retrieve ts,txrx-gpio from dts\n");
		return PTR_ERR(ts_nbus->txrx);
		}

		ts_nbus->strobe = devm_gpiod_get(&pdev->dev, "ts,strobe", GPIOD_OUT_HIGH);
		if (IS_ERR(ts_nbus->strobe)) {
		dev_err(&pdev->dev, "failed to retrieve ts,strobe-gpio from dts\n");
		return PTR_ERR(ts_nbus->strobe);
		}

		ts_nbus->ale = devm_gpiod_get(&pdev->dev, "ts,ale", GPIOD_OUT_HIGH);
		if (IS_ERR(ts_nbus->ale)) {
		dev_err(&pdev->dev, "failed to retrieve ts,ale-gpio from dts\n");
		return PTR_ERR(ts_nbus->ale);
		}

		ts_nbus->rdy = devm_gpiod_get(&pdev->dev, "ts,rdy", GPIOD_IN);
		if (IS_ERR(ts_nbus->rdy)) {
		dev_err(&pdev->dev, "failed to retrieve ts,rdy-gpio from dts\n");
		return PTR_ERR(ts_nbus->rdy);
		}

		return 0;
		}

		/*
		* the data gpios are used for reading and writing values, their directions
		* should be adjusted accordingly.
		*/
		static void ts_nbus_set_direction(struct ts_nbus *ts_nbus, int direction)
		{
		int i;

		for (i = 0; i < 8; i++) {
		if (direction == TS_NBUS_DIRECTION_IN)
		gpiod_direction_input(ts_nbus->data->desc[i]);
		else
		/* when used as output the default state of the data
		* lines are set to high */
		gpiod_direction_output(ts_nbus->data->desc[i], 1);
		}
		}

		/*
		* reset the bus in its initial state.
		* The data, csn, strobe and ale lines must be zero'ed to let the FPGA knows a
		* new transaction can be process.
		*/
		static void ts_nbus_reset_bus(struct ts_nbus *ts_nbus)
		{
		int i;
		int values[8];

		for (i = 0; i < 8; i++)
		values[i] = 0;

		gpiod_set_array_value_cansleep(8, ts_nbus->data->desc, values);
		gpiod_set_value_cansleep(ts_nbus->csn, 0);
		gpiod_set_value_cansleep(ts_nbus->strobe, 0);
		gpiod_set_value_cansleep(ts_nbus->ale, 0);
		}

		/*
		* let the FPGA knows it can process.
		*/
		static void ts_nbus_start_transaction(struct ts_nbus *ts_nbus)
		{
		gpiod_set_value_cansleep(ts_nbus->strobe, 1);
		}

		/*
		* read a byte value from the data gpios.
		* return 0 on success or negative errno on failure.
		*/
		static int ts_nbus_read_byte(struct ts_nbus ts_nbus, u8 val)
		{
		struct gpio_descs *gpios = ts_nbus->data;
		int ret, i;

		*val = 0;
		for (i = 0; i < 8; i++) {
		ret = gpiod_get_value_cansleep(gpios->desc[i]);
		if (ret < 0)
		return ret;
		if (ret)
		*val \|= BIT(i);
		}

		return 0;
		}

		/*
		* set the data gpios accordingly to the byte value.
		*/
		static void ts_nbus_write_byte(struct ts_nbus *ts_nbus, u8 byte)
		{
		struct gpio_descs *gpios = ts_nbus->data;
		int i;
		int values[8];

		for (i = 0; i < 8; i++)
		if (byte & BIT(i))
		values[i] = 1;
		else
		values[i] = 0;

		gpiod_set_array_value_cansleep(8, gpios->desc, values);
		}

		/*
		* reading the bus consists of resetting the bus, then notifying the FPGA to
		* send the data in the data gpios and return the read value.
		* return 0 on success or negative errno on failure.
		*/
		static int ts_nbus_read_bus(struct ts_nbus ts_nbus, u8 val)
		{
		ts_nbus_reset_bus(ts_nbus);
		ts_nbus_start_transaction(ts_nbus);

		return ts_nbus_read_byte(ts_nbus, val);
		}

		/*
		* writing to the bus consists of resetting the bus, then define the type of
		* command (address/value), write the data and notify the FPGA to retrieve the
		* value in the data gpios.
		*/
		static void ts_nbus_write_bus(struct ts_nbus *ts_nbus, int cmd, u8 val)
		{
		ts_nbus_reset_bus(ts_nbus);

		if (cmd == TS_NBUS_WRITE_ADR)
		gpiod_set_value_cansleep(ts_nbus->ale, 1);

		ts_nbus_write_byte(ts_nbus, val);
		ts_nbus_start_transaction(ts_nbus);
		}

		/*
		* read the value in the FPGA register at the given address.
		* return 0 on success or negative errno on failure.
		*/
		int ts_nbus_read(struct ts_nbus ts_nbus, u8 adr, u16 val)
		{
		int ret, i;
		u8 byte;

		/* bus access must be atomic */
		mutex_lock(&ts_nbus->lock);

		/* set the bus in read mode */
		gpiod_set_value_cansleep(ts_nbus->txrx, 0);

		/* write address */
		ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);

		/* set the data gpios direction as input before reading */
		ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_IN);

		/* reading value MSB first */
		do {
		*val = 0;
		byte = 0;
		for (i = 1; i >= 0; i--) {
		/* read a byte from the bus, leave on error */
		ret = ts_nbus_read_bus(ts_nbus, &byte);
		if (ret < 0)
		goto err;

		/* append the byte read to the final value */
		val \|= byte << (i 8);
		}
		gpiod_set_value_cansleep(ts_nbus->csn, 1);
		ret = gpiod_get_value_cansleep(ts_nbus->rdy);
		} while (ret);

		err:
		/* restore the data gpios direction as output after reading */
		ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_OUT);

		mutex_unlock(&ts_nbus->lock);

		return ret;
		}
		EXPORT_SYMBOL_GPL(ts_nbus_read);

		/*
		* write the desired value in the FPGA register at the given address.
		*/
		int ts_nbus_write(struct ts_nbus *ts_nbus, u8 adr, u16 val)
		{
		int i;

		/* bus access must be atomic */
		mutex_lock(&ts_nbus->lock);

		/* set the bus in write mode */
		gpiod_set_value_cansleep(ts_nbus->txrx, 1);

		/* write address */
		ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);

		/* writing value MSB first */
		for (i = 1; i >= 0; i--)
		ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_VAL, (u8)(val >> (i * 8)));

		/* wait for completion */
		gpiod_set_value_cansleep(ts_nbus->csn, 1);
		while (gpiod_get_value_cansleep(ts_nbus->rdy) != 0) {
		gpiod_set_value_cansleep(ts_nbus->csn, 0);
		gpiod_set_value_cansleep(ts_nbus->csn, 1);
		}

		mutex_unlock(&ts_nbus->lock);

		return 0;
		}
		EXPORT_SYMBOL_GPL(ts_nbus_write);

		static int ts_nbus_probe(struct platform_device *pdev)
		{
		struct pwm_device *pwm;
		struct pwm_args pargs;
		struct device *dev = &pdev->dev;
		struct ts_nbus *ts_nbus;
		int ret;

		ts_nbus = devm_kzalloc(dev, sizeof(*ts_nbus), GFP_KERNEL);
		if (!ts_nbus)
		return -ENOMEM;

		mutex_init(&ts_nbus->lock);

		ret = ts_nbus_init_pdata(pdev, ts_nbus);
		if (ret < 0)
		return ret;

		pwm = devm_pwm_get(dev, NULL);
		if (IS_ERR(pwm)) {
		ret = PTR_ERR(pwm);
		if (ret != -EPROBE_DEFER)
		dev_err(dev, "unable to request PWM\n");
		return ret;
		}

		pwm_get_args(pwm, &pargs);
		if (!pargs.period) {
		dev_err(&pdev->dev, "invalid PWM period\n");
		return -EINVAL;
		}

		/*
		* FIXME: pwm_apply_args() should be removed when switching to
		* the atomic PWM API.
		*/
		pwm_apply_args(pwm);
		ret = pwm_config(pwm, pargs.period, pargs.period);
		if (ret < 0)
		return ret;

		/*
		* we can now start the FPGA and populate the peripherals.
		*/
		pwm_enable(pwm);
		ts_nbus->pwm = pwm;

		/*
		* let the child nodes retrieve this instance of the ts-nbus.
		*/
		dev_set_drvdata(dev, ts_nbus);

		ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
		if (ret < 0)
		return ret;

		dev_info(dev, "initialized\n");

		return 0;
		}

		static int ts_nbus_remove(struct platform_device *pdev)
		{
		struct ts_nbus *ts_nbus = dev_get_drvdata(&pdev->dev);

		/* shutdown the FPGA */
		mutex_lock(&ts_nbus->lock);
		pwm_disable(ts_nbus->pwm);
		mutex_unlock(&ts_nbus->lock);

		return 0;
		}

		static const struct of_device_id ts_nbus_of_match[] = {
		{ .compatible = "technologic,ts-nbus", },
		{ },
		};
		MODULE_DEVICE_TABLE(of, ts_nbus_of_match);

		static struct platform_driver ts_nbus_driver = {
		.probe = ts_nbus_probe,
		.remove = ts_nbus_remove,
		.driver = {
		.name = "ts_nbus",
		.of_match_table = ts_nbus_of_match,
		},
		};

		module_platform_driver(ts_nbus_driver);

		MODULE_ALIAS("platform:ts_nbus");
		MODULE_AUTHOR("Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>");
		MODULE_DESCRIPTION("Technologic Systems NBUS");
		MODULE_LICENSE("GPL v2");

include/linux/ts-nbus.h

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		/*
		* Copyright (c) 2016 - Savoir-faire Linux
		* Author: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
		*
		* This file is licensed under the terms of the GNU General Public
		* License version 2. This program is licensed "as is" without any
		* warranty of any kind, whether express or implied.
		*/

		#ifndef _TS_NBUS_H
		#define _TS_NBUS_H

		struct ts_nbus;

		extern int ts_nbus_read(struct ts_nbus ts_nbus, u8 adr, u16 val);
		extern int ts_nbus_write(struct ts_nbus *ts_nbus, u8 adr, u16 val);

		#endif /* _TS_NBUS_H */