Commit df1d80ae authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Jonathan Cameron
Browse files

iio: ad_sigma_delta: Properly handle SPI bus locking vs CS assertion 



For devices from the SigmaDelta family we need to keep CS low when doing a
conversion, since the device will use the MISO line as a interrupt to
indicate that the conversion is complete.

This is why the driver locks the SPI bus and when the SPI bus is locked
keeps as long as a conversion is going on. The current implementation gets
one small detail wrong though. CS is only de-asserted after the SPI bus is
unlocked. This means it is possible for a different SPI device on the same
bus to send a message which would be wrongfully be addressed to the
SigmaDelta device as well. Make sure that the last SPI transfer that is
done while holding the SPI bus lock de-asserts the CS signal.

Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: default avatarAlexandru Ardelean <Alexandru.Ardelean@analog.com>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent 6ec417d2

drivers/iio/adc/ad_sigma_delta.c

+11 −5
Original line number Diff line number Diff line
@@ -62,7 +62,7 @@ int ad_sd_write_reg(struct ad_sigma_delta *sigma_delta, unsigned int reg, 
	struct spi_transfer t = {

		.tx_buf		= data,

		.len		= size + 1,

		.cs_change	= sigma_delta->bus_locked,

		.cs_change	= sigma_delta->keep_cs_asserted,

	};

	struct spi_message m;

	int ret;
@@ -217,6 +217,7 @@ static int ad_sd_calibrate(struct ad_sigma_delta *sigma_delta, 


	spi_bus_lock(sigma_delta->spi->master);

	sigma_delta->bus_locked = true;

	sigma_delta->keep_cs_asserted = true;

	reinit_completion(&sigma_delta->completion);



	ret = ad_sigma_delta_set_mode(sigma_delta, mode);
@@ -234,9 +235,10 @@ static int ad_sd_calibrate(struct ad_sigma_delta *sigma_delta, 
		ret = 0;

	}

out:

	sigma_delta->keep_cs_asserted = false;

	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);

	sigma_delta->bus_locked = false;

	spi_bus_unlock(sigma_delta->spi->master);

	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);



	return ret;

}
@@ -289,6 +291,7 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev, 


	spi_bus_lock(sigma_delta->spi->master);

	sigma_delta->bus_locked = true;

	sigma_delta->keep_cs_asserted = true;

	reinit_completion(&sigma_delta->completion);



	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_SINGLE);
@@ -298,9 +301,6 @@ int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev, 
	ret = wait_for_completion_interruptible_timeout(

			&sigma_delta->completion, HZ);



	sigma_delta->bus_locked = false;

	spi_bus_unlock(sigma_delta->spi->master);



	if (ret == 0)

		ret = -EIO;

	if (ret < 0)
@@ -321,7 +321,10 @@ out: 
		sigma_delta->irq_dis = true;

	}



	sigma_delta->keep_cs_asserted = false;

	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);

	sigma_delta->bus_locked = false;

	spi_bus_unlock(sigma_delta->spi->master);

	mutex_unlock(&indio_dev->mlock);



	if (ret)
@@ -358,6 +361,8 @@ static int ad_sd_buffer_postenable(struct iio_dev *indio_dev) 


	spi_bus_lock(sigma_delta->spi->master);

	sigma_delta->bus_locked = true;

	sigma_delta->keep_cs_asserted = true;



	ret = ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_CONTINUOUS);

	if (ret)

		goto err_unlock;
@@ -386,6 +391,7 @@ static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev) 
		sigma_delta->irq_dis = true;

	}



	sigma_delta->keep_cs_asserted = false;

	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);



	sigma_delta->bus_locked = false;

include/linux/iio/adc/ad_sigma_delta.h

+1 −0
Original line number Diff line number Diff line
@@ -69,6 +69,7 @@ struct ad_sigma_delta { 
	bool			irq_dis;



	bool			bus_locked;

	bool			keep_cs_asserted;



	uint8_t			comm;

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