Patch "iio: accel: bmc150: reset chip at init time" has been added to the 4.7-stable tree

This is a note to let you know that I've just added the patch titled

iio: accel: bmc150: reset chip at init time

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iio-accel-bmc150-reset-chip-at-init-time.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Olof Johansson <[email protected]>
Date: Thu, 25 Aug 2016 09:45:33 -0700
Subject: iio: accel: bmc150: reset chip at init time

From: Olof Johansson <[email protected]>

commit 1c500840934a138bd6b13556c210516e9301fbee upstream.

In at least one known setup, the chip comes up in a state where reading the chip ID returns garbage unless it's been reset, due to noise on the wires during system boot.

All supported chips have the same reset method, and based on the datasheets they all need 1.3 or 1.8ms to recover after reset. So, do the conservative thing here and always reset the chip.

---
 drivers/iio/accel/bmc150-accel-core.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

@@ -67,6 +67,9 @@
 #define BMC150_ACCEL_REG_PMU_BW		0x10
 #define BMC150_ACCEL_DEF_BW			125
 
+#define BMC150_ACCEL_REG_RESET			0x14
+#define BMC150_ACCEL_RESET_VAL			0xB6
+
 #define BMC150_ACCEL_REG_INT_MAP_0		0x19
 #define BMC150_ACCEL_INT_MAP_0_BIT_SLOPE	BIT(2)
 

@@ -1497,6 +1500,14 @@ static int bmc150_accel_chip_init(struct
 	int ret, i;
 	unsigned int val;
 
+	/*
+	 * Reset chip to get it in a known good state. A delay of 1.8ms after
+	 * reset is required according to the data sheets of supported chips.
+	 */
+	regmap_write(data->regmap, BMC150_ACCEL_REG_RESET,
+		     BMC150_ACCEL_RESET_VAL);
+	usleep_range(1800, 2500);
+
 	ret = regmap_read(data->regmap, BMC150_ACCEL_REG_CHIP_ID, &val);
 	if (ret < 0) {
 		dev_err(dev, "Error: Reading chip id\n");

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/iio-accel-bmc150-reset-chip-at-init-time.patch