From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:46164 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933483AbcIVNmi (ORCPT ); Thu, 22 Sep 2016 09:42:38 -0400 Subject: Patch "iio: accel: bmc150: reset chip at init time" has been added to the 4.4-stable tree To: olof@lixom.net, gregkh@linuxfoundation.org, jic23@kernel.org, srinivas.pandruvada@linux.intel.com Cc: , From: Date: Thu, 22 Sep 2016 15:41:44 +0200 Message-ID: <1474551704202214@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 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 4.4-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-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 1c500840934a138bd6b13556c210516e9301fbee Mon Sep 17 00:00:00 2001 From: Olof Johansson Date: Thu, 25 Aug 2016 09:45:33 -0700 Subject: iio: accel: bmc150: reset chip at init time From: Olof Johansson 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. Signed-off-by: Olof Johansson Reviewed-by: Srinivas Pandruvada Signed-off-by: Jonathan Cameron Signed-off-by: Greg Kroah-Hartman --- drivers/iio/accel/bmc150-accel-core.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/drivers/iio/accel/bmc150-accel-core.c +++ b/drivers/iio/accel/bmc150-accel-core.c @@ -68,6 +68,9 @@ #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) @@ -1487,6 +1490,14 @@ 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(data->dev, Patches currently in stable-queue which might be from olof@lixom.net are queue-4.4/iio-accel-bmc150-reset-chip-at-init-time.patch