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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: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <Alexandru.Ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Lars-Peter Clausen 2019-03-19 13:37:55 +02:00 committed by Jonathan Cameron
parent 6ec417d2f1
commit df1d80aee9
2 changed files with 12 additions and 5 deletions
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16
drivers/iio/adc/ad_sigma_delta.c
View File

@ -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;

1
include/linux/iio/adc/ad_sigma_delta.h
View File

@ -69,6 +69,7 @@ struct ad_sigma_delta {
bool irq_dis;
bool bus_locked;
bool keep_cs_asserted;
uint8_t comm;