patch "iio: accel: bmc150: reset chip at init time" added to staging-linus

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 my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

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

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(+)

index bf17aae66145..59b380dbf27f 100644
@@ -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 bmc150_accel_data *data)
 	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");

2.9.3