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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * NBUS driver for TS-4600 based boards4 *5 * Copyright (c) 2016 - Savoir-faire Linux6 * Author: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>7 *8 * This driver implements a GPIOs bit-banged bus, called the NBUS by Technologic9 * Systems. It is used to communicate with the peripherals in the FPGA on the10 * TS-4600 SoM.11 */12 13#include <linux/bitops.h>14#include <linux/gpio/consumer.h>15#include <linux/kernel.h>16#include <linux/module.h>17#include <linux/mutex.h>18#include <linux/of_platform.h>19#include <linux/platform_device.h>20#include <linux/pwm.h>21#include <linux/ts-nbus.h>22 23#define TS_NBUS_DIRECTION_IN 024#define TS_NBUS_DIRECTION_OUT 125#define TS_NBUS_WRITE_ADR 026#define TS_NBUS_WRITE_VAL 127 28struct ts_nbus {29 struct pwm_device *pwm;30 struct gpio_descs *data;31 struct gpio_desc *csn;32 struct gpio_desc *txrx;33 struct gpio_desc *strobe;34 struct gpio_desc *ale;35 struct gpio_desc *rdy;36 struct mutex lock;37};38 39/*40 * request all gpios required by the bus.41 */42static int ts_nbus_init_pdata(struct platform_device *pdev,43 struct ts_nbus *ts_nbus)44{45 ts_nbus->data = devm_gpiod_get_array(&pdev->dev, "ts,data",46 GPIOD_OUT_HIGH);47 if (IS_ERR(ts_nbus->data))48 return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->data),49 "failed to retrieve ts,data-gpio from dts\n");50 51 ts_nbus->csn = devm_gpiod_get(&pdev->dev, "ts,csn", GPIOD_OUT_HIGH);52 if (IS_ERR(ts_nbus->csn))53 return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->csn),54 "failed to retrieve ts,csn-gpio from dts\n");55 56 ts_nbus->txrx = devm_gpiod_get(&pdev->dev, "ts,txrx", GPIOD_OUT_HIGH);57 if (IS_ERR(ts_nbus->txrx))58 return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->txrx),59 "failed to retrieve ts,txrx-gpio from dts\n");60 61 ts_nbus->strobe = devm_gpiod_get(&pdev->dev, "ts,strobe", GPIOD_OUT_HIGH);62 if (IS_ERR(ts_nbus->strobe))63 return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->strobe),64 "failed to retrieve ts,strobe-gpio from dts\n");65 66 ts_nbus->ale = devm_gpiod_get(&pdev->dev, "ts,ale", GPIOD_OUT_HIGH);67 if (IS_ERR(ts_nbus->ale))68 return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->ale),69 "failed to retrieve ts,ale-gpio from dts\n");70 71 ts_nbus->rdy = devm_gpiod_get(&pdev->dev, "ts,rdy", GPIOD_IN);72 if (IS_ERR(ts_nbus->rdy))73 return dev_err_probe(&pdev->dev, PTR_ERR(ts_nbus->rdy),74 "failed to retrieve ts,rdy-gpio from dts\n");75 76 return 0;77}78 79/*80 * the data gpios are used for reading and writing values, their directions81 * should be adjusted accordingly.82 */83static void ts_nbus_set_direction(struct ts_nbus *ts_nbus, int direction)84{85 int i;86 87 for (i = 0; i < 8; i++) {88 if (direction == TS_NBUS_DIRECTION_IN)89 gpiod_direction_input(ts_nbus->data->desc[i]);90 else91 /* when used as output the default state of the data92 * lines are set to high */93 gpiod_direction_output(ts_nbus->data->desc[i], 1);94 }95}96 97/*98 * reset the bus in its initial state.99 * The data, csn, strobe and ale lines must be zero'ed to let the FPGA knows a100 * new transaction can be process.101 */102static void ts_nbus_reset_bus(struct ts_nbus *ts_nbus)103{104 DECLARE_BITMAP(values, 8);105 106 values[0] = 0;107 108 gpiod_set_array_value_cansleep(8, ts_nbus->data->desc,109 ts_nbus->data->info, values);110 gpiod_set_value_cansleep(ts_nbus->csn, 0);111 gpiod_set_value_cansleep(ts_nbus->strobe, 0);112 gpiod_set_value_cansleep(ts_nbus->ale, 0);113}114 115/*116 * let the FPGA knows it can process.117 */118static void ts_nbus_start_transaction(struct ts_nbus *ts_nbus)119{120 gpiod_set_value_cansleep(ts_nbus->strobe, 1);121}122 123/*124 * read a byte value from the data gpios.125 * return 0 on success or negative errno on failure.126 */127static int ts_nbus_read_byte(struct ts_nbus *ts_nbus, u8 *val)128{129 struct gpio_descs *gpios = ts_nbus->data;130 int ret, i;131 132 *val = 0;133 for (i = 0; i < 8; i++) {134 ret = gpiod_get_value_cansleep(gpios->desc[i]);135 if (ret < 0)136 return ret;137 if (ret)138 *val |= BIT(i);139 }140 141 return 0;142}143 144/*145 * set the data gpios accordingly to the byte value.146 */147static void ts_nbus_write_byte(struct ts_nbus *ts_nbus, u8 byte)148{149 struct gpio_descs *gpios = ts_nbus->data;150 DECLARE_BITMAP(values, 8);151 152 values[0] = byte;153 154 gpiod_set_array_value_cansleep(8, gpios->desc, gpios->info, values);155}156 157/*158 * reading the bus consists of resetting the bus, then notifying the FPGA to159 * send the data in the data gpios and return the read value.160 * return 0 on success or negative errno on failure.161 */162static int ts_nbus_read_bus(struct ts_nbus *ts_nbus, u8 *val)163{164 ts_nbus_reset_bus(ts_nbus);165 ts_nbus_start_transaction(ts_nbus);166 167 return ts_nbus_read_byte(ts_nbus, val);168}169 170/*171 * writing to the bus consists of resetting the bus, then define the type of172 * command (address/value), write the data and notify the FPGA to retrieve the173 * value in the data gpios.174 */175static void ts_nbus_write_bus(struct ts_nbus *ts_nbus, int cmd, u8 val)176{177 ts_nbus_reset_bus(ts_nbus);178 179 if (cmd == TS_NBUS_WRITE_ADR)180 gpiod_set_value_cansleep(ts_nbus->ale, 1);181 182 ts_nbus_write_byte(ts_nbus, val);183 ts_nbus_start_transaction(ts_nbus);184}185 186/*187 * read the value in the FPGA register at the given address.188 * return 0 on success or negative errno on failure.189 */190int ts_nbus_read(struct ts_nbus *ts_nbus, u8 adr, u16 *val)191{192 int ret, i;193 u8 byte;194 195 /* bus access must be atomic */196 mutex_lock(&ts_nbus->lock);197 198 /* set the bus in read mode */199 gpiod_set_value_cansleep(ts_nbus->txrx, 0);200 201 /* write address */202 ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);203 204 /* set the data gpios direction as input before reading */205 ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_IN);206 207 /* reading value MSB first */208 do {209 *val = 0;210 byte = 0;211 for (i = 1; i >= 0; i--) {212 /* read a byte from the bus, leave on error */213 ret = ts_nbus_read_bus(ts_nbus, &byte);214 if (ret < 0)215 goto err;216 217 /* append the byte read to the final value */218 *val |= byte << (i * 8);219 }220 gpiod_set_value_cansleep(ts_nbus->csn, 1);221 ret = gpiod_get_value_cansleep(ts_nbus->rdy);222 } while (ret);223 224err:225 /* restore the data gpios direction as output after reading */226 ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_OUT);227 228 mutex_unlock(&ts_nbus->lock);229 230 return ret;231}232EXPORT_SYMBOL_GPL(ts_nbus_read);233 234/*235 * write the desired value in the FPGA register at the given address.236 */237int ts_nbus_write(struct ts_nbus *ts_nbus, u8 adr, u16 val)238{239 int i;240 241 /* bus access must be atomic */242 mutex_lock(&ts_nbus->lock);243 244 /* set the bus in write mode */245 gpiod_set_value_cansleep(ts_nbus->txrx, 1);246 247 /* write address */248 ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);249 250 /* writing value MSB first */251 for (i = 1; i >= 0; i--)252 ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_VAL, (u8)(val >> (i * 8)));253 254 /* wait for completion */255 gpiod_set_value_cansleep(ts_nbus->csn, 1);256 while (gpiod_get_value_cansleep(ts_nbus->rdy) != 0) {257 gpiod_set_value_cansleep(ts_nbus->csn, 0);258 gpiod_set_value_cansleep(ts_nbus->csn, 1);259 }260 261 mutex_unlock(&ts_nbus->lock);262 263 return 0;264}265EXPORT_SYMBOL_GPL(ts_nbus_write);266 267static int ts_nbus_probe(struct platform_device *pdev)268{269 struct pwm_device *pwm;270 struct pwm_state state;271 struct device *dev = &pdev->dev;272 struct ts_nbus *ts_nbus;273 int ret;274 275 ts_nbus = devm_kzalloc(dev, sizeof(*ts_nbus), GFP_KERNEL);276 if (!ts_nbus)277 return -ENOMEM;278 279 mutex_init(&ts_nbus->lock);280 281 ret = ts_nbus_init_pdata(pdev, ts_nbus);282 if (ret < 0)283 return ret;284 285 pwm = devm_pwm_get(dev, NULL);286 if (IS_ERR(pwm))287 return dev_err_probe(dev, PTR_ERR(pwm),288 "unable to request PWM\n");289 290 pwm_init_state(pwm, &state);291 if (!state.period)292 return dev_err_probe(dev, -EINVAL, "invalid PWM period\n");293 294 state.duty_cycle = state.period;295 state.enabled = true;296 297 ret = pwm_apply_might_sleep(pwm, &state);298 if (ret < 0)299 return dev_err_probe(dev, ret, "failed to configure PWM\n");300 301 /*302 * we can now start the FPGA and populate the peripherals.303 */304 ts_nbus->pwm = pwm;305 306 /*307 * let the child nodes retrieve this instance of the ts-nbus.308 */309 dev_set_drvdata(dev, ts_nbus);310 311 ret = of_platform_populate(dev->of_node, NULL, NULL, dev);312 if (ret < 0)313 return dev_err_probe(dev, ret,314 "failed to populate platform devices on bus\n");315 316 dev_info(dev, "initialized\n");317 318 return 0;319}320 321static void ts_nbus_remove(struct platform_device *pdev)322{323 struct ts_nbus *ts_nbus = dev_get_drvdata(&pdev->dev);324 325 /* shutdown the FPGA */326 mutex_lock(&ts_nbus->lock);327 pwm_disable(ts_nbus->pwm);328 mutex_unlock(&ts_nbus->lock);329}330 331static const struct of_device_id ts_nbus_of_match[] = {332 { .compatible = "technologic,ts-nbus", },333 { },334};335MODULE_DEVICE_TABLE(of, ts_nbus_of_match);336 337static struct platform_driver ts_nbus_driver = {338 .probe = ts_nbus_probe,339 .remove_new = ts_nbus_remove,340 .driver = {341 .name = "ts_nbus",342 .of_match_table = ts_nbus_of_match,343 },344};345 346module_platform_driver(ts_nbus_driver);347 348MODULE_ALIAS("platform:ts_nbus");349MODULE_AUTHOR("Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>");350MODULE_DESCRIPTION("Technologic Systems NBUS");351MODULE_LICENSE("GPL v2");352