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From: Petre Rodan <petre.rodan@subdimension.ro>
To: linux-iio@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: Petre Rodan <petre.rodan@subdimension.ro>,
	Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>
Subject: [PATCH 4/6] iio: pressure: hsc030pa add mandatory delay
Date: Wed, 10 Jan 2024 19:22:39 +0200
Message-ID: <20240110172306.31273-5-petre.rodan@subdimension.ro>
In-Reply-To: <20240110172306.31273-1-petre.rodan@subdimension.ro>
References: <20240110172306.31273-1-petre.rodan@subdimension.ro>
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Add a mandatory 2ms delay between consecutive chip reads.

I found a new Technical Note pdf that specifies that the measurement cycle
in these chips takes around 1.26ms. By adding this 2ms delay we make sure
that we never get stale measurements.

This feature is also needed by the "iio: pressure: hsc030pa add sleep mode"
patch below.

For more details, please see "Figure 1" in the pdf below:

https://prod-edam.honeywell.com/content/dam/honeywell-edam/sps/siot/en-us/products/sensors/pressure-sensors/common/documents/sps-siot-sleep-mode-technical-note-008286-1-en-ciid-155793.pdf

Signed-off-by: Petre Rodan <petre.rodan@subdimension.ro>
---
 drivers/iio/pressure/hsc030pa.h     | 1 +
 drivers/iio/pressure/hsc030pa_i2c.c | 3 +++
 drivers/iio/pressure/hsc030pa_spi.c | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/drivers/iio/pressure/hsc030pa.h b/drivers/iio/pressure/hsc030pa.h
index f1079a70799f..56dc8e88194b 100644
--- a/drivers/iio/pressure/hsc030pa.h
+++ b/drivers/iio/pressure/hsc030pa.h
@@ -13,6 +13,7 @@
 #include <linux/iio/iio.h>

 #define HSC_REG_MEASUREMENT_RD_SIZE 4
+#define HSC_RESP_TIME_MS            2

 struct device;

diff --git a/drivers/iio/pressure/hsc030pa_i2c.c b/drivers/iio/pressure/hsc030pa_i2c.c
index b5810bafef40..b3fd230e71da 100644
--- a/drivers/iio/pressure/hsc030pa_i2c.c
+++ b/drivers/iio/pressure/hsc030pa_i2c.c
@@ -8,6 +8,7 @@
  * Datasheet: https://prod-edam.honeywell.com/content/dam/honeywell-edam/sps/siot/en-us/products/sensors/pressure-sensors/common/documents/sps-siot-sleep-mode-technical-note-008286-1-en-ciid-155793.pdf
  */

+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/errno.h>
 #include <linux/i2c.h>
@@ -25,6 +26,8 @@ static int hsc_i2c_recv(struct hsc_data *data)
 	struct i2c_msg msg;
 	int ret;

+	msleep_interruptible(HSC_RESP_TIME_MS);
+
 	msg.addr = client->addr;
 	msg.flags = client->flags | I2C_M_RD;
 	msg.len = HSC_REG_MEASUREMENT_RD_SIZE;
diff --git a/drivers/iio/pressure/hsc030pa_spi.c b/drivers/iio/pressure/hsc030pa_spi.c
index 8d3441f1dcf9..737197eddff0 100644
--- a/drivers/iio/pressure/hsc030pa_spi.c
+++ b/drivers/iio/pressure/hsc030pa_spi.c
@@ -8,6 +8,7 @@
  * Datasheet: https://prod-edam.honeywell.com/content/dam/honeywell-edam/sps/siot/en-us/products/sensors/pressure-sensors/common/documents/sps-siot-sleep-mode-technical-note-008286-1-en-ciid-155793.pdf
  */

+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
@@ -28,6 +29,8 @@ static int hsc_spi_recv(struct hsc_data *data)
 		.len = HSC_REG_MEASUREMENT_RD_SIZE,
 	};

+	msleep_interruptible(HSC_RESP_TIME_MS);
+
 	return spi_sync_transfer(spi, &xfer, 1);
 }

--
2.41.0