linux-kernel - [PATCH AUTOSEL for 4.9 24/24] iio: adc: ti-ads1015: add 10% to conversion wait time

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Date:   Wed, 22 Nov 2017 22:26:16 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Ladislav Michl <ladis@...ux-mips.org>,
        Daniel Baluta <daniel.baluta@...il.com>,
        Jonathan Cameron <jic23@...nel.org>,
        "Jonathan Cameron" <Jonathan.Cameron@...wei.com>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.9 24/24] iio: adc: ti-ads1015: add 10% to
 conversion wait time

From: Ladislav Michl <ladis@...ux-mips.org>

[ Upstream commit fe895ac88b9fbdf2026f0bfd56c82747bb9d7c48 ]

As user's guide "ADS1015EVM, ADS1115EVM, ADS1015EVM-PDK, ADS1115EVM-PDK
User Guide (Rev. B)" (http://www.ti.com/lit/ug/sbau157b/sbau157b.pdf)
states at page 16:
"Note that both the ADS1115 and ADS1015 have internal clocks with a ±10%
accuracy. If performing FFT tests, frequencies may appear to be incorrect
as a result of this tolerance range.", add those 10% to converion wait
time.

Cc: Daniel Baluta <daniel.baluta@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>
Signed-off-by: Ladislav Michl <ladis@...ux-mips.org>
Reviewed-by: Akinobu Mita <akinobu.mita@...il.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/iio/adc/ti-ads1015.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c
index 472641fc890c..af05e20c986b 100644
--- a/drivers/iio/adc/ti-ads1015.c
+++ b/drivers/iio/adc/ti-ads1015.c
@@ -269,6 +269,7 @@ int ads1015_get_adc_result(struct ads1015_data *data, int chan, int *val)
 
 		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr_old]);
 		conv_time += DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
+		conv_time += conv_time / 10; /* 10% internal clock inaccuracy */
 		usleep_range(conv_time, conv_time + 1);
 		data->conv_invalid = false;
 	}
-- 
2.11.0