diff options
| author | Alexandru Ardelean <alexandru.ardelean@analog.com> | 2018-11-23 22:23:08 -0200 |
|---|---|---|
| committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2018-12-01 15:35:33 +0000 |
| commit | 11d509adfbe04f9eff49a17eed5d686472b435f4 (patch) | |
| tree | 521d8596af703182f0ed0488c7963174a7b9267b /drivers/staging/iio/resolver | |
| parent | a996590baddca587d91d07e264d2649b84788b17 (diff) | |
staging:iio:ad2s90: Add max frequency check at probe
This patch adds a max frequency check at the beginning of ad2s90_probe
function so that when it is set to a value above 0.83Mhz, dev_err is
called with an appropriate message and -EINVAL is returned.
The defined limit is 0.83Mhz instead of 2Mhz, which is the chip's max
frequency as specified in the datasheet, because, as also specified in
the datasheet, a 600ns delay is expected between the application of a
logic LO to CS and the application of SCLK. Since the delay is not
implemented in the spi code, to satisfy it, SCLK's period should be at
most 2 * 600ns, so the max frequency should be 1 / (2 * 6e-7), which
gives roughly 830000Hz.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Diffstat (limited to 'drivers/staging/iio/resolver')
| -rw-r--r-- | drivers/staging/iio/resolver/ad2s90.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/staging/iio/resolver/ad2s90.c b/drivers/staging/iio/resolver/ad2s90.c index abb9b9147ee6..4721e9bbb8b0 100644 --- a/drivers/staging/iio/resolver/ad2s90.c +++ b/drivers/staging/iio/resolver/ad2s90.c @@ -19,6 +19,12 @@ #include <linux/iio/iio.h> #include <linux/iio/sysfs.h> +/* + * Although chip's max frequency is 2Mhz, it needs 600ns between CS and the + * first falling edge of SCLK, so frequency should be at most 1 / (2 * 6e-7) + */ +#define AD2S90_MAX_SPI_FREQ_HZ 830000 + struct ad2s90_state { struct mutex lock; struct spi_device *sdev; @@ -78,6 +84,12 @@ static int ad2s90_probe(struct spi_device *spi) struct iio_dev *indio_dev; struct ad2s90_state *st; + if (spi->max_speed_hz > AD2S90_MAX_SPI_FREQ_HZ) { + dev_err(&spi->dev, "SPI CLK, %d Hz exceeds %d Hz\n", + spi->max_speed_hz, AD2S90_MAX_SPI_FREQ_HZ); + return -EINVAL; + } + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st)); if (!indio_dev) return -ENOMEM; |