iio: pressure: mprls0025pa: move memset to core

Move memset() from the bus specific code into core.

Zeroing out the buffer is performed because the sensor has noticeable
latch-up sensitivity and in some cases it clamps the MISO signal to GND
in sync with SCLK [1]. A raw conversion of zero is out of bounds since
valid values have to be between output_min and output_max (and the
smallest output_min is 2.5% of 2^24 = 419430).

The user is expected to discard out of bounds pressure values.

Given the fact that we can't follow the behaviour of all SPI controllers
when faced to this clamping of an output signal, a raw conversion of zero
is used as an early warning in case the low level SPI API reacts
unexpectedly.

Link: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1588325/am3358-spi-tx-data-corruption
Signed-off-by: Petre Rodan <petre.rodan@subdimension.ro>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/pressure/mprls0025pa.c b/drivers/iio/pressure/mprls0025pa.c
index 2bcd339dc84e99e21d8f2a4f636aa08e2aa44e61..a7041a503bde5e226c4401785be316c1af025467 100644 (file)
--- a/drivers/iio/pressure/mprls0025pa.c
+++ b/drivers/iio/pressure/mprls0025pa.c
@@ -22,6 +22,7 @@
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/property.h>
+#include <linux/string.h>
 #include <linux/units.h>
 
 #include <linux/gpio/consumer.h>
@@ -247,6 +248,7 @@ static int mpr_read_pressure(struct mpr_data *data, s32 *press)
                }
        }
 
+       memset(data->rx_buf, 0, sizeof(data->rx_buf));
        ret = data->ops->read(data, MPR_CMD_NOP, MPR_PKT_NOP_LEN);
        if (ret < 0)
                return ret;

diff --git a/drivers/iio/pressure/mprls0025pa_i2c.c b/drivers/iio/pressure/mprls0025pa_i2c.c
index a0bbc6af928312c2fe0b0b021c8b70c7bd7c560a..0fe8cfe0d7e7fb98d4fb7f53292d8224b6dda249 100644 (file)
--- a/drivers/iio/pressure/mprls0025pa_i2c.c
+++ b/drivers/iio/pressure/mprls0025pa_i2c.c
@@ -25,7 +25,6 @@ static int mpr_i2c_read(struct mpr_data *data, const u8 unused, const u8 cnt)
        if (cnt > MPR_MEASUREMENT_RD_SIZE)
                return -EOVERFLOW;
 
-       memset(data->rx_buf, 0, MPR_MEASUREMENT_RD_SIZE);
        ret = i2c_master_recv(client, data->rx_buf, cnt);
        if (ret < 0)
                return ret;