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: Matheus Tavares <matheus.bernardino@xxxxxx>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
---
Alex's S-o-B was added because he gave the code suggestion for this
patch.
drivers/staging/iio/resolver/ad2s90.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/staging/iio/resolver/ad2s90.c b/drivers/staging/iio/resolver/ad2s90.c
index 95c118c48400..949ff55ac6b0 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;
--
2.18.0
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