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![Sergiu Cuciurean](/assets/img/avatar_default.png)
As part of the general cleanup of indio_dev->mlock, this change replaces it with a local lock on the device's state from potential concurrent write accesses from userspace. The write operation requires an SPI write, then toggling of a GPIO, so the lock aims to protect the sanity of the entire sequence of operation. This is part of a bigger cleanup. Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/ Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com> Link: https://lore.kernel.org/r/20200916092535.76527-1-alexandru.ardelean@analog.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
193 lines
4.5 KiB
C
193 lines
4.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* DAC7612 Dual, 12-Bit Serial input Digital-to-Analog Converter
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*
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* Copyright 2019 Qtechnology A/S
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* 2019 Ricardo Ribalda <ribalda@kernel.org>
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*
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* Licensed under the GPL-2.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/spi/spi.h>
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#include <linux/gpio/consumer.h>
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#include <linux/iio/iio.h>
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#define DAC7612_RESOLUTION 12
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#define DAC7612_ADDRESS 4
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#define DAC7612_START 5
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struct dac7612 {
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struct spi_device *spi;
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struct gpio_desc *loaddacs;
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uint16_t cache[2];
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/*
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* Lock to protect the state of the device from potential concurrent
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* write accesses from userspace. The write operation requires an
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* SPI write, then toggling of a GPIO, so the lock aims to protect
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* the sanity of the entire sequence of operation.
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*/
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struct mutex lock;
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/*
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* DMA (thus cache coherency maintenance) requires the
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* transfer buffers to live in their own cache lines.
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*/
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uint8_t data[2] ____cacheline_aligned;
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};
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static int dac7612_cmd_single(struct dac7612 *priv, int channel, u16 val)
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{
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int ret;
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priv->data[0] = BIT(DAC7612_START) | (channel << DAC7612_ADDRESS);
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priv->data[0] |= val >> 8;
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priv->data[1] = val & 0xff;
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priv->cache[channel] = val;
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ret = spi_write(priv->spi, priv->data, sizeof(priv->data));
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if (ret)
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return ret;
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gpiod_set_value(priv->loaddacs, 1);
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gpiod_set_value(priv->loaddacs, 0);
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return 0;
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}
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#define dac7612_CHANNEL(chan, name) { \
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.type = IIO_VOLTAGE, \
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.channel = (chan), \
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.indexed = 1, \
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.output = 1, \
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.datasheet_name = name, \
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.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
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.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
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}
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static const struct iio_chan_spec dac7612_channels[] = {
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dac7612_CHANNEL(0, "OUTA"),
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dac7612_CHANNEL(1, "OUTB"),
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};
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static int dac7612_read_raw(struct iio_dev *iio_dev,
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const struct iio_chan_spec *chan,
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int *val, int *val2, long mask)
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{
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struct dac7612 *priv;
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switch (mask) {
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case IIO_CHAN_INFO_RAW:
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priv = iio_priv(iio_dev);
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*val = priv->cache[chan->channel];
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return IIO_VAL_INT;
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case IIO_CHAN_INFO_SCALE:
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*val = 1;
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return IIO_VAL_INT;
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default:
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return -EINVAL;
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}
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}
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static int dac7612_write_raw(struct iio_dev *iio_dev,
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const struct iio_chan_spec *chan,
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int val, int val2, long mask)
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{
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struct dac7612 *priv = iio_priv(iio_dev);
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int ret;
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if (mask != IIO_CHAN_INFO_RAW)
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return -EINVAL;
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if ((val >= BIT(DAC7612_RESOLUTION)) || val < 0 || val2)
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return -EINVAL;
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if (val == priv->cache[chan->channel])
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return 0;
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mutex_lock(&priv->lock);
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ret = dac7612_cmd_single(priv, chan->channel, val);
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mutex_unlock(&priv->lock);
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return ret;
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}
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static const struct iio_info dac7612_info = {
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.read_raw = dac7612_read_raw,
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.write_raw = dac7612_write_raw,
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};
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static int dac7612_probe(struct spi_device *spi)
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{
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struct iio_dev *iio_dev;
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struct dac7612 *priv;
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int i;
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int ret;
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iio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*priv));
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if (!iio_dev)
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return -ENOMEM;
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priv = iio_priv(iio_dev);
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/*
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* LOADDACS pin can be controlled by the driver or externally.
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* When controlled by the driver, the DAC value is updated after
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* every write.
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* When the driver does not control the PIN, the user or an external
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* event can change the value of all DACs by pulsing down the LOADDACs
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* pin.
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*/
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priv->loaddacs = devm_gpiod_get_optional(&spi->dev, "ti,loaddacs",
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GPIOD_OUT_LOW);
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if (IS_ERR(priv->loaddacs))
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return PTR_ERR(priv->loaddacs);
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priv->spi = spi;
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spi_set_drvdata(spi, iio_dev);
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iio_dev->info = &dac7612_info;
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iio_dev->modes = INDIO_DIRECT_MODE;
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iio_dev->channels = dac7612_channels;
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iio_dev->num_channels = ARRAY_SIZE(priv->cache);
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iio_dev->name = spi_get_device_id(spi)->name;
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mutex_init(&priv->lock);
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for (i = 0; i < ARRAY_SIZE(priv->cache); i++) {
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ret = dac7612_cmd_single(priv, i, 0);
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if (ret)
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return ret;
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}
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return devm_iio_device_register(&spi->dev, iio_dev);
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}
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static const struct spi_device_id dac7612_id[] = {
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{"ti-dac7612"},
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{}
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};
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MODULE_DEVICE_TABLE(spi, dac7612_id);
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static const struct of_device_id dac7612_of_match[] = {
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{ .compatible = "ti,dac7612" },
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{ .compatible = "ti,dac7612u" },
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{ .compatible = "ti,dac7612ub" },
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{ },
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};
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MODULE_DEVICE_TABLE(of, dac7612_of_match);
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static struct spi_driver dac7612_driver = {
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.driver = {
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.name = "ti-dac7612",
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.of_match_table = dac7612_of_match,
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},
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.probe = dac7612_probe,
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.id_table = dac7612_id,
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};
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module_spi_driver(dac7612_driver);
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MODULE_AUTHOR("Ricardo Ribalda <ribalda@kernel.org>");
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MODULE_DESCRIPTION("Texas Instruments DAC7612 DAC driver");
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MODULE_LICENSE("GPL v2");
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