linux-kernel - [PATCH v2 2/2] iio: hx711: fix bug in reset functionality

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Message-ID: <20171130214445.GA27345@arbeit>
Date:   Thu, 30 Nov 2017 22:44:45 +0100
From:   Andreas Klinger <ak@...klinger.de>
To:     jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net, singhalsimran0@...il.com,
        linux-iio@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] iio: hx711: fix bug in reset functionality

return value in hx711_reset() should indicate status of dout
otherwise the calling function is reporting an error als false positive

wait up to 1 second until the device is in normal state
by changing the channel on every trigger event it turned out that the
former 100 ms are not enough for waiting until the device is in normal mode

Signed-off-by: Andreas Klinger <ak@...klinger.de>
---
 drivers/iio/adc/hx711.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c
index d773fd69a76d..eabd2e66aca3 100644
--- a/drivers/iio/adc/hx711.c
+++ b/drivers/iio/adc/hx711.c
@@ -153,15 +153,16 @@ static int hx711_wait_for_ready(struct hx711_data *hx711_data)
 	int i, val;
 
 	/*
-	 * a maximum reset cycle time of 56 ms was measured.
-	 * we round it up to 100 ms
+	 * in some rare cases the reset takes quite a long time
+	 * especially when the channel is changed.
+	 * Allow up to one second for it
 	 */
 	for (i = 0; i < 100; i++) {
 		val = gpiod_get_value(hx711_data->gpiod_dout);
 		if (!val)
 			break;
-		/* sleep at least 1 ms */
-		msleep(1);
+		/* sleep at least 10 ms */
+		msleep(10);
 	}
 	if (val)
 		return -EIO;
@@ -203,9 +204,7 @@ static int hx711_reset(struct hx711_data *hx711_data)
 		 * after a dummy read we need to wait vor readiness
 		 * for not mixing gain pulses with the clock
 		 */
-		ret = hx711_wait_for_ready(hx711_data);
-		if (ret)
-			return ret;
+		val = hx711_wait_for_ready(hx711_data);
 	}
 
 	return val;
-- 
2.1.4


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