linux-kernel - [PATCH v3] iio: humidity: hdc100x: Add margin to the conversion time

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Date:   Mon, 14 Jun 2021 09:18:20 -0500
From:   Chris Lesiak <chris.lesiak@...or.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Lesiak <chris.lesiak@...or.com>
Subject: [PATCH v3] iio: humidity: hdc100x: Add margin to the conversion time

The datasheets have the following note for the conversion time
specification: "This parameter is specified by design and/or
characterization and it is not tested in production."

Parts have been seen that require more time to do 14-bit conversions for
the relative humidity channel.  The result is ENXIO due to the address
phase of a transfer not getting an ACK.

Delay an additional 1 ms per conversion to allow for additional margin.

Fixes: 4839367d99e3 ("iio: humidity: add HDC100x support")
Signed-off-by: Chris Lesiak <chris.lesiak@...or.com>
---
 drivers/iio/humidity/hdc100x.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c
index 2a957f19048e..9e0fce917ce4 100644
--- a/drivers/iio/humidity/hdc100x.c
+++ b/drivers/iio/humidity/hdc100x.c
@@ -25,6 +25,8 @@
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
 
+#include <linux/time.h>
+
 #define HDC100X_REG_TEMP			0x00
 #define HDC100X_REG_HUMIDITY			0x01
 
@@ -166,7 +168,7 @@ static int hdc100x_get_measurement(struct hdc100x_data *data,
 				   struct iio_chan_spec const *chan)
 {
 	struct i2c_client *client = data->client;
-	int delay = data->adc_int_us[chan->address];
+	int delay = data->adc_int_us[chan->address] + 1*USEC_PER_MSEC;
 	int ret;
 	__be16 val;
 
@@ -316,7 +318,7 @@ static irqreturn_t hdc100x_trigger_handler(int irq, void *p)
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct hdc100x_data *data = iio_priv(indio_dev);
 	struct i2c_client *client = data->client;
-	int delay = data->adc_int_us[0] + data->adc_int_us[1];
+	int delay = data->adc_int_us[0] + data->adc_int_us[1] + 2*USEC_PER_MSEC;
 	int ret;
 
 	/* dual read starts at temp register */
-- 
2.26.2