linux-kernel - [PATCH 4.19 54/65] iio: light: vcnl4000: update sampling periods for vcnl4200

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Date:   Tue, 24 Mar 2020 14:11:15 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Guido Günther <agx@...xcpu.org>,
        Tomas Novotny <tomas@...otny.cz>, Stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 54/65] iio: light: vcnl4000: update sampling periods for vcnl4200

From: Tomas Novotny <tomas@...otny.cz>

[ Upstream commit b42aa97ed5f1169cfd37175ef388ea62ff2dcf43 ]

Vishay has published a new version of "Designing the VCNL4200 Into an
Application" application note in October 2019. The new version specifies
that there is +-20% of part to part tolerance. This explains the drift
seen during experiments. The proximity pulse width is also changed from
32us to 30us. According to the support, the tolerance also applies to
ambient light.

So update the sampling periods. As the reading is blocking, current
users may notice slightly longer response time.

Fixes: be38866fbb97 ("iio: vcnl4000: add support for VCNL4200")
Reviewed-by: Guido Günther <agx@...xcpu.org>
Signed-off-by: Tomas Novotny <tomas@...otny.cz>
Cc: <Stable@...r.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iio/light/vcnl4000.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/light/vcnl4000.c b/drivers/iio/light/vcnl4000.c
index 04fd0d4b6f198..d3d65ecb30a5b 100644
--- a/drivers/iio/light/vcnl4000.c
+++ b/drivers/iio/light/vcnl4000.c
@@ -150,9 +150,10 @@ static int vcnl4200_init(struct vcnl4000_data *data)
 	data->al_scale = 24000;
 	data->vcnl4200_al.reg = VCNL4200_AL_DATA;
 	data->vcnl4200_ps.reg = VCNL4200_PS_DATA;
-	/* Integration time is 50ms, but the experiments show 54ms in total. */
-	data->vcnl4200_al.sampling_rate = ktime_set(0, 54000 * 1000);
-	data->vcnl4200_ps.sampling_rate = ktime_set(0, 4200 * 1000);
+	/* Default wait time is 50ms, add 20% tolerance. */
+	data->vcnl4200_al.sampling_rate = ktime_set(0, 60000 * 1000);
+	/* Default wait time is 4.8ms, add 20% tolerance. */
+	data->vcnl4200_ps.sampling_rate = ktime_set(0, 5760 * 1000);
 	data->vcnl4200_al.last_measurement = ktime_set(0, 0);
 	data->vcnl4200_ps.last_measurement = ktime_set(0, 0);
 	mutex_init(&data->vcnl4200_al.lock);
-- 
2.20.1