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[PATCH 4.4 11/32] iio: bmg160: reset chip when probing

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Quentin Schulz <quentin.schulz@free-electrons.com>

commit 4bdc9029685ac03be50b320b29691766d2326c2b upstream.

The gyroscope chip might need to be reset to be used.

Without the chip being reset, the driver stopped at the first
regmap_read (to get the CHIP_ID) and failed to probe.

The datasheet of the gyroscope says that a minimum wait of 30ms after
the reset has to be done.

This patch has been checked on a BMX055 and the datasheet of the BMG160
and the BMI055 give the same reset register and bits.

Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/iio/gyro/bmg160_core.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/drivers/iio/gyro/bmg160_core.c
+++ b/drivers/iio/gyro/bmg160_core.c
@@ -28,6 +28,7 @@
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
 #include <linux/regmap.h>
+#include <linux/delay.h>
 #include "bmg160.h"
 
 #define BMG160_IRQ_NAME		"bmg160_event"
@@ -53,6 +54,9 @@
 #define BMG160_NO_FILTER		0
 #define BMG160_DEF_BW			100
 
+#define BMG160_GYRO_REG_RESET		0x14
+#define BMG160_GYRO_RESET_VAL		0xb6
+
 #define BMG160_REG_INT_MAP_0		0x17
 #define BMG160_INT_MAP_0_BIT_ANY	BIT(1)
 
@@ -186,6 +190,14 @@ static int bmg160_chip_init(struct bmg16
 	int ret;
 	unsigned int val;
 
+	/*
+	 * Reset chip to get it in a known good state. A delay of 30ms after
+	 * reset is required according to the datasheet.
+	 */
+	regmap_write(data->regmap, BMG160_GYRO_REG_RESET,
+		     BMG160_GYRO_RESET_VAL);
+	usleep_range(30000, 30700);
+
 	ret = regmap_read(data->regmap, BMG160_REG_CHIP_ID, &val);
 	if (ret < 0) {
 		dev_err(data->dev, "Error reading reg_chip_id\n");

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[PATCH 4.4 00/32] 4.4.61-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 05/32] drm/vmwgfx: Remove getparam error message Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 01/32] drm/vmwgfx: Type-check lookups of fence objects Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 06/32] drm/vmwgfx: fix integer overflow in vmw_surface_define_ioctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 28/32] MIPS: ralink: Fix typos in rt3883 pinctrl Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 09/32] arm/arm64: KVM: Take mmap_sem in stage2_unmap_vm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 16/32] metag/usercopy: Fix alignment error checking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 30/32] MIPS: Lantiq: fix missing xbar kernel panic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 32/32] mm/mempolicy.c: fix error handling in set_mempolicy and mbind. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 23/32] powerpc: Dont try to fix up misaligned load-with-reservation instructions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 20/32] metag/usercopy: Fix src fixup in from user rapf loops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 08/32] staging: android: ashmem: lseek failed due to no FMODE_LSEEK. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 29/32] MIPS: End spinlocks with .insn Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6 kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
    Re: [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6  kernels "Maciej W. Rozycki" <macro@linux-mips.org> - 2017-04-15 01:50 +0200
      Re: [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6  kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 15:20 +0200
  [PATCH 4.4 26/32] s390/uaccess: get_user() should zero on failure (again) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 31/32] MIPS: Flush wrong invalid FTLB entry for huge page Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 14/32] ring-buffer: Fix return value check in test_ringbuffer() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 17/32] metag/usercopy: Add early abort to copy_to_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 22/32] powerpc/mm: Add missing global TLB invalidate if cxl is active Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 04/32] drm/ttm, drm/vmwgfx: Relax permission checking when opening surfaces Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 25/32] s390/decompressor: fix initrd corruption caused by bss clear Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 15/32] metag/usercopy: Drop unused macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 24/32] nios2: reserve boot memory for device tree Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 21/32] metag/usercopy: Add missing fixups Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 11/32] iio: bmg160: reset chip when probing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 19/32] metag/usercopy: Set flags before ADDZ Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 13/32] ptrace: fix PTRACE_LISTEN race corrupting task->state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 18/32] metag/usercopy: Zero rest of buffer from copy_from_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 10/32] arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 12/32] Reset TreeId to zero on SMB2 TREE_CONNECT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 02/32] drm/vmwgfx: NULL pointer dereference in vmw_surface_define_ioctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 07/32] sysfs: be careful of error returns from ops->show() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  Re: [PATCH 4.4 00/32] 4.4.61-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-04-10 22:40 +0200

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