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369 lines
8.9 KiB
369 lines
8.9 KiB
/* |
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* NBUS driver for TS-4600 based boards |
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* |
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* Copyright (c) 2016 - Savoir-faire Linux |
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* Author: Sebastien Bourdelin <[email protected]> |
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* |
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* This file is licensed under the terms of the GNU General Public |
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* License version 2. This program is licensed "as is" without any |
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* warranty of any kind, whether express or implied. |
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* |
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* This driver implements a GPIOs bit-banged bus, called the NBUS by Technologic |
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* Systems. It is used to communicate with the peripherals in the FPGA on the |
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* TS-4600 SoM. |
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*/ |
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#include <linux/bitops.h> |
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#include <linux/gpio/consumer.h> |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/mutex.h> |
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#include <linux/of_platform.h> |
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#include <linux/platform_device.h> |
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#include <linux/pwm.h> |
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#include <linux/ts-nbus.h> |
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#define TS_NBUS_DIRECTION_IN 0 |
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#define TS_NBUS_DIRECTION_OUT 1 |
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#define TS_NBUS_WRITE_ADR 0 |
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#define TS_NBUS_WRITE_VAL 1 |
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struct ts_nbus { |
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struct pwm_device *pwm; |
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struct gpio_descs *data; |
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struct gpio_desc *csn; |
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struct gpio_desc *txrx; |
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struct gpio_desc *strobe; |
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struct gpio_desc *ale; |
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struct gpio_desc *rdy; |
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struct mutex lock; |
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}; |
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/* |
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* request all gpios required by the bus. |
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*/ |
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static int ts_nbus_init_pdata(struct platform_device *pdev, struct ts_nbus |
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*ts_nbus) |
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{ |
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ts_nbus->data = devm_gpiod_get_array(&pdev->dev, "ts,data", |
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GPIOD_OUT_HIGH); |
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if (IS_ERR(ts_nbus->data)) { |
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dev_err(&pdev->dev, "failed to retrieve ts,data-gpio from dts\n"); |
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return PTR_ERR(ts_nbus->data); |
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} |
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ts_nbus->csn = devm_gpiod_get(&pdev->dev, "ts,csn", GPIOD_OUT_HIGH); |
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if (IS_ERR(ts_nbus->csn)) { |
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dev_err(&pdev->dev, "failed to retrieve ts,csn-gpio from dts\n"); |
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return PTR_ERR(ts_nbus->csn); |
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} |
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ts_nbus->txrx = devm_gpiod_get(&pdev->dev, "ts,txrx", GPIOD_OUT_HIGH); |
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if (IS_ERR(ts_nbus->txrx)) { |
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dev_err(&pdev->dev, "failed to retrieve ts,txrx-gpio from dts\n"); |
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return PTR_ERR(ts_nbus->txrx); |
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} |
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ts_nbus->strobe = devm_gpiod_get(&pdev->dev, "ts,strobe", GPIOD_OUT_HIGH); |
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if (IS_ERR(ts_nbus->strobe)) { |
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dev_err(&pdev->dev, "failed to retrieve ts,strobe-gpio from dts\n"); |
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return PTR_ERR(ts_nbus->strobe); |
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} |
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ts_nbus->ale = devm_gpiod_get(&pdev->dev, "ts,ale", GPIOD_OUT_HIGH); |
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if (IS_ERR(ts_nbus->ale)) { |
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dev_err(&pdev->dev, "failed to retrieve ts,ale-gpio from dts\n"); |
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return PTR_ERR(ts_nbus->ale); |
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} |
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ts_nbus->rdy = devm_gpiod_get(&pdev->dev, "ts,rdy", GPIOD_IN); |
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if (IS_ERR(ts_nbus->rdy)) { |
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dev_err(&pdev->dev, "failed to retrieve ts,rdy-gpio from dts\n"); |
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return PTR_ERR(ts_nbus->rdy); |
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} |
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return 0; |
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} |
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/* |
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* the data gpios are used for reading and writing values, their directions |
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* should be adjusted accordingly. |
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*/ |
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static void ts_nbus_set_direction(struct ts_nbus *ts_nbus, int direction) |
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{ |
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int i; |
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for (i = 0; i < 8; i++) { |
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if (direction == TS_NBUS_DIRECTION_IN) |
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gpiod_direction_input(ts_nbus->data->desc[i]); |
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else |
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/* when used as output the default state of the data |
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* lines are set to high */ |
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gpiod_direction_output(ts_nbus->data->desc[i], 1); |
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} |
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} |
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/* |
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* reset the bus in its initial state. |
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* The data, csn, strobe and ale lines must be zero'ed to let the FPGA knows a |
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* new transaction can be process. |
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*/ |
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static void ts_nbus_reset_bus(struct ts_nbus *ts_nbus) |
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{ |
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DECLARE_BITMAP(values, 8); |
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values[0] = 0; |
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gpiod_set_array_value_cansleep(8, ts_nbus->data->desc, |
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ts_nbus->data->info, values); |
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gpiod_set_value_cansleep(ts_nbus->csn, 0); |
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gpiod_set_value_cansleep(ts_nbus->strobe, 0); |
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gpiod_set_value_cansleep(ts_nbus->ale, 0); |
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} |
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/* |
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* let the FPGA knows it can process. |
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*/ |
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static void ts_nbus_start_transaction(struct ts_nbus *ts_nbus) |
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{ |
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gpiod_set_value_cansleep(ts_nbus->strobe, 1); |
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} |
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/* |
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* read a byte value from the data gpios. |
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* return 0 on success or negative errno on failure. |
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*/ |
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static int ts_nbus_read_byte(struct ts_nbus *ts_nbus, u8 *val) |
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{ |
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struct gpio_descs *gpios = ts_nbus->data; |
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int ret, i; |
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*val = 0; |
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for (i = 0; i < 8; i++) { |
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ret = gpiod_get_value_cansleep(gpios->desc[i]); |
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if (ret < 0) |
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return ret; |
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if (ret) |
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*val |= BIT(i); |
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} |
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return 0; |
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} |
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/* |
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* set the data gpios accordingly to the byte value. |
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*/ |
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static void ts_nbus_write_byte(struct ts_nbus *ts_nbus, u8 byte) |
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{ |
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struct gpio_descs *gpios = ts_nbus->data; |
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DECLARE_BITMAP(values, 8); |
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values[0] = byte; |
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gpiod_set_array_value_cansleep(8, gpios->desc, gpios->info, values); |
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} |
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/* |
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* reading the bus consists of resetting the bus, then notifying the FPGA to |
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* send the data in the data gpios and return the read value. |
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* return 0 on success or negative errno on failure. |
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*/ |
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static int ts_nbus_read_bus(struct ts_nbus *ts_nbus, u8 *val) |
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{ |
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ts_nbus_reset_bus(ts_nbus); |
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ts_nbus_start_transaction(ts_nbus); |
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return ts_nbus_read_byte(ts_nbus, val); |
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} |
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/* |
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* writing to the bus consists of resetting the bus, then define the type of |
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* command (address/value), write the data and notify the FPGA to retrieve the |
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* value in the data gpios. |
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*/ |
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static void ts_nbus_write_bus(struct ts_nbus *ts_nbus, int cmd, u8 val) |
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{ |
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ts_nbus_reset_bus(ts_nbus); |
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if (cmd == TS_NBUS_WRITE_ADR) |
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gpiod_set_value_cansleep(ts_nbus->ale, 1); |
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ts_nbus_write_byte(ts_nbus, val); |
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ts_nbus_start_transaction(ts_nbus); |
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} |
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/* |
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* read the value in the FPGA register at the given address. |
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* return 0 on success or negative errno on failure. |
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*/ |
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int ts_nbus_read(struct ts_nbus *ts_nbus, u8 adr, u16 *val) |
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{ |
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int ret, i; |
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u8 byte; |
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/* bus access must be atomic */ |
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mutex_lock(&ts_nbus->lock); |
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/* set the bus in read mode */ |
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gpiod_set_value_cansleep(ts_nbus->txrx, 0); |
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/* write address */ |
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ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr); |
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/* set the data gpios direction as input before reading */ |
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ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_IN); |
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/* reading value MSB first */ |
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do { |
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*val = 0; |
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byte = 0; |
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for (i = 1; i >= 0; i--) { |
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/* read a byte from the bus, leave on error */ |
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ret = ts_nbus_read_bus(ts_nbus, &byte); |
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if (ret < 0) |
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goto err; |
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/* append the byte read to the final value */ |
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*val |= byte << (i * 8); |
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} |
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gpiod_set_value_cansleep(ts_nbus->csn, 1); |
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ret = gpiod_get_value_cansleep(ts_nbus->rdy); |
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} while (ret); |
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err: |
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/* restore the data gpios direction as output after reading */ |
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ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_OUT); |
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mutex_unlock(&ts_nbus->lock); |
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return ret; |
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} |
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EXPORT_SYMBOL_GPL(ts_nbus_read); |
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/* |
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* write the desired value in the FPGA register at the given address. |
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*/ |
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int ts_nbus_write(struct ts_nbus *ts_nbus, u8 adr, u16 val) |
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{ |
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int i; |
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/* bus access must be atomic */ |
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mutex_lock(&ts_nbus->lock); |
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/* set the bus in write mode */ |
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gpiod_set_value_cansleep(ts_nbus->txrx, 1); |
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/* write address */ |
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ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr); |
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/* writing value MSB first */ |
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for (i = 1; i >= 0; i--) |
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ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_VAL, (u8)(val >> (i * 8))); |
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/* wait for completion */ |
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gpiod_set_value_cansleep(ts_nbus->csn, 1); |
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while (gpiod_get_value_cansleep(ts_nbus->rdy) != 0) { |
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gpiod_set_value_cansleep(ts_nbus->csn, 0); |
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gpiod_set_value_cansleep(ts_nbus->csn, 1); |
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} |
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mutex_unlock(&ts_nbus->lock); |
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return 0; |
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} |
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EXPORT_SYMBOL_GPL(ts_nbus_write); |
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static int ts_nbus_probe(struct platform_device *pdev) |
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{ |
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struct pwm_device *pwm; |
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struct pwm_args pargs; |
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struct device *dev = &pdev->dev; |
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struct ts_nbus *ts_nbus; |
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int ret; |
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ts_nbus = devm_kzalloc(dev, sizeof(*ts_nbus), GFP_KERNEL); |
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if (!ts_nbus) |
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return -ENOMEM; |
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mutex_init(&ts_nbus->lock); |
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ret = ts_nbus_init_pdata(pdev, ts_nbus); |
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if (ret < 0) |
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return ret; |
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pwm = devm_pwm_get(dev, NULL); |
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if (IS_ERR(pwm)) { |
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ret = PTR_ERR(pwm); |
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if (ret != -EPROBE_DEFER) |
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dev_err(dev, "unable to request PWM\n"); |
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return ret; |
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} |
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pwm_get_args(pwm, &pargs); |
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if (!pargs.period) { |
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dev_err(&pdev->dev, "invalid PWM period\n"); |
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return -EINVAL; |
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} |
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/* |
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* FIXME: pwm_apply_args() should be removed when switching to |
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* the atomic PWM API. |
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*/ |
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pwm_apply_args(pwm); |
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ret = pwm_config(pwm, pargs.period, pargs.period); |
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if (ret < 0) |
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return ret; |
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/* |
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* we can now start the FPGA and populate the peripherals. |
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*/ |
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pwm_enable(pwm); |
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ts_nbus->pwm = pwm; |
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/* |
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* let the child nodes retrieve this instance of the ts-nbus. |
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*/ |
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dev_set_drvdata(dev, ts_nbus); |
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ret = of_platform_populate(dev->of_node, NULL, NULL, dev); |
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if (ret < 0) |
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return ret; |
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dev_info(dev, "initialized\n"); |
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return 0; |
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} |
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static int ts_nbus_remove(struct platform_device *pdev) |
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{ |
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struct ts_nbus *ts_nbus = dev_get_drvdata(&pdev->dev); |
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/* shutdown the FPGA */ |
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mutex_lock(&ts_nbus->lock); |
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pwm_disable(ts_nbus->pwm); |
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mutex_unlock(&ts_nbus->lock); |
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return 0; |
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} |
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static const struct of_device_id ts_nbus_of_match[] = { |
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{ .compatible = "technologic,ts-nbus", }, |
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{ }, |
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}; |
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MODULE_DEVICE_TABLE(of, ts_nbus_of_match); |
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static struct platform_driver ts_nbus_driver = { |
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.probe = ts_nbus_probe, |
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.remove = ts_nbus_remove, |
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.driver = { |
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.name = "ts_nbus", |
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.of_match_table = ts_nbus_of_match, |
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}, |
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}; |
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module_platform_driver(ts_nbus_driver); |
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MODULE_ALIAS("platform:ts_nbus"); |
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MODULE_AUTHOR("Sebastien Bourdelin <[email protected]>"); |
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MODULE_DESCRIPTION("Technologic Systems NBUS"); |
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MODULE_LICENSE("GPL v2");
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