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Commit ba272e3b authored by Katie Dunne's avatar Katie Dunne Committed by Jonathan Cameron
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Staging: iio: meter: ade7759: update locking method for write frequency 

iio_dev->mlock is to be used only by the IIO core for protecting
device mode changes between INDIO_DIRECT and INDIO_BUFFER.

This patch replaces the use of mlock with the already established
buf_lock mutex.

Introducing an 'unlocked' spi_write_reg_16 function to be used by
ade7759_write_frequency avoids nested locks and maintains atomicity
between bus and device frequency changes.

Based on the solution found in ade7754 patch here:
https://marc.info/?l=linux-iio&m=149086659008991&w=2



Signed-off-by: default avatarKatie Dunne <kdunne@mail.ccsf.edu>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent 08969366

drivers/staging/iio/meter/ade7759.c

+19 −8
Original line number Diff line number Diff line
@@ -60,7 +60,7 @@ 
/**

 * struct ade7759_state - device instance specific data

 * @us:			actual spi_device

 * @buf_lock:		mutex to protect tx and rx

 * @buf_lock:		mutex to protect tx and rx and write frequency

 * @tx:			transmit buffer

 * @rx:			receive buffer

 **/
@@ -89,19 +89,30 @@ static int ade7759_spi_write_reg_8(struct device *dev, 
	return ret;

}



static int ade7759_spi_write_reg_16(struct device *dev,

/*Unlocked version of ade7759_spi_write_reg_16 function */

static int __ade7759_spi_write_reg_16(struct device *dev,

		u8 reg_address,

		u16 value)

{

	int ret;

	struct iio_dev *indio_dev = dev_to_iio_dev(dev);

	struct ade7759_state *st = iio_priv(indio_dev);



	mutex_lock(&st->buf_lock);

	st->tx[0] = ADE7759_WRITE_REG(reg_address);

	st->tx[1] = (value >> 8) & 0xFF;

	st->tx[2] = value & 0xFF;

	ret = spi_write(st->us, st->tx, 3);

	return spi_write(st->us, st->tx, 3);

}



static int ade7759_spi_write_reg_16(struct device *dev,

		u8 reg_address,

		u16 value)

{

	int ret;

	struct iio_dev *indio_dev = dev_to_iio_dev(dev);

	struct ade7759_state *st = iio_priv(indio_dev);



	mutex_lock(&st->buf_lock);

	ret = __ade7759_spi_write_reg_16(dev, reg_address, value);

	mutex_unlock(&st->buf_lock);



	return ret;
@@ -429,7 +440,7 @@ static ssize_t ade7759_write_frequency(struct device *dev, 
	if (!val)

		return -EINVAL;



	mutex_lock(&indio_dev->mlock);

	mutex_lock(&st->buf_lock);



	t = 27900 / val;

	if (t > 0)
@@ -447,10 +458,10 @@ static ssize_t ade7759_write_frequency(struct device *dev, 
	reg &= ~(3 << 13);

	reg |= t << 13;



	ret = ade7759_spi_write_reg_16(dev, ADE7759_MODE, reg);

	ret = __ade7759_spi_write_reg_16(dev, ADE7759_MODE, reg);



out:

	mutex_unlock(&indio_dev->mlock);

	mutex_unlock(&st->buf_lock);



	return ret ? ret : len;

}