// SPDX-License-Identifier: GPL-2.0-only
/*
* NBUS driver for TS-4600 based boards
*
* Copyright (c) 2016 - Savoir-faire Linux
* Author: Sebastien Bourdelin <[email protected]>
*
* 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))
return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->data),
"failed to retrieve ts,data-gpio from dts\n");
ts_nbus->csn = devm_gpiod_get(&pdev->dev, "ts,csn", GPIOD_OUT_HIGH);
if (IS_ERR(ts_nbus->csn))
return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->csn),
"failed to retrieve ts,csn-gpio from dts\n");
ts_nbus->txrx = devm_gpiod_get(&pdev->dev, "ts,txrx", GPIOD_OUT_HIGH);
if (IS_ERR(ts_nbus->txrx))
return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->txrx),
"failed to retrieve ts,txrx-gpio from dts\n");
ts_nbus->strobe = devm_gpiod_get(&pdev->dev, "ts,strobe", GPIOD_OUT_HIGH);
if (IS_ERR(ts_nbus->strobe))
return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->strobe),
"failed to retrieve ts,strobe-gpio from dts\n");
ts_nbus->ale = devm_gpiod_get(&pdev->dev, "ts,ale", GPIOD_OUT_HIGH);
if (IS_ERR(ts_nbus->ale))
return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->ale),
"failed to retrieve ts,ale-gpio from dts\n");
ts_nbus->rdy = devm_gpiod_get(&pdev->dev, "ts,rdy", GPIOD_IN);
if (IS_ERR(ts_nbus->rdy))
return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->rdy),
"failed to retrieve ts,rdy-gpio from dts\n");
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)
{
DECLARE_BITMAP(values, 8);
values[0] = 0;
gpiod_set_array_value_cansleep(8, ts_nbus->data->desc,
ts_nbus->data->info, 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;
DECLARE_BITMAP(values, 8);
values[0] = byte;
gpiod_set_array_value_cansleep(8, gpios->desc, gpios->info, 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_state state;
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))
return dev_err_probe(dev, PTR_ERR(pwm),
"unable to request PWM\n");
pwm_init_state(pwm, &state);
if (!state.period)
return dev_err_probe(dev, -EINVAL, "invalid PWM period\n");
state.duty_cycle = state.period;
state.enabled = true;
ret = pwm_apply_might_sleep(pwm, &state);
if (ret < 0)
return dev_err_probe(dev, ret, "failed to configure PWM\n");
/*
* we can now start the FPGA and populate the peripherals.
*/
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 dev_err_probe(dev, ret,
"failed to populate platform devices on bus\n");
dev_info(dev, "initialized\n");
return 0;
}
static void 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);
}
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_new = 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 <[email protected]>");
MODULE_DESCRIPTION("Technologic Systems NBUS");
MODULE_LICENSE("GPL v2");
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