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[RFC PATCH 0/9] iio: Fix ABBA deadlock in inv-mpu6050

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  [RFC PATCH 0/9] iio: Fix ABBA deadlock in inv-mpu6050 Daniel Baluta <daniel.baluta@intel.com> - 2016-02-18 17:00 +0100
    Re: [RFC PATCH 0/9] iio: Fix ABBA deadlock in inv-mpu6050 Wolfram Sang <wsa@the-dreams.de> - 2016-02-22 00:20 +0100
      Re: [RFC PATCH 0/9] iio: Fix ABBA deadlock in inv-mpu6050 Daniel Baluta <daniel.baluta@intel.com> - 2016-02-22 10:50 +0100

#1337485 — [RFC PATCH 0/9] iio: Fix ABBA deadlock in inv-mpu6050

Sending this as an RFC because I don't know if style fixes are appropriate
for this driver and also not sure if deadlock fix is the best solution.

I2C people should only look at patches 8/9 and 9/9.

The mpu6050 accel+gyro combo has an auxiliary I2C bus, allowing for
an auxiliary sensor to be connected (eg. a magnetometer).

The mpu can either act as an I2C master (functionality not currently
implemented in the driver) or it can use a bypass multiplexer which
directly connects the auxiliary I2C bus pins to the main I2C bus pins [1]
Currently the driver implements the bypass mode via an I2C mux.

This patchset fixes a deadlock in inv-mpu6050 IMU which happens when
magnetometer (on auxiliary I2C bus) runs in parallel with accel or gyro.

First 7 patches do some cleanup in order to make INV MPU6050 code easier
to read.

Patch number 8 allows passing NULL select callbacks to i2c_mux_master_xfer
and i2c_mux_smbus_xfer.

Patch number 9 actually fixes the deadlock.

[1] (page 28, https://www.cdiweb.com/datasheets/invensense/MPU-6050_DataSheet_V3%204.pdf)

Adriana Reus (2):
  i2c: i2c-mux: Allow for NULL select callback
  iio: imu: inv_mpu6050: Fix deadlock between i2c adapter lock and mpu
    lock

Daniel Baluta (7):
  iio: imu: inv_mpu6050: Fix multiline comments style
  iio: imu: inv_mpu6050: Fix Yoda conditions
  iio: imu: inv_mpu6050: Fix newlines to make code easier to read
  iio: imu: inv_mpu6050: Remove unnecessary parentheses
  iio: imu: inv_mpu6050: Delete space before comma
  iio: imu: inv_mpu6050: Fix code indent for if statement
  iio: imu: inv_mpu6050: Fix alignment with open parenthesis

 drivers/i2c/i2c-mux.c                         |  10 ++-
 drivers/iio/imu/inv_mpu6050/inv_mpu_acpi.c    |   6 +-
 drivers/iio/imu/inv_mpu6050/inv_mpu_core.c    | 101 ++++++++++++++------------
 drivers/iio/imu/inv_mpu6050/inv_mpu_i2c.c     |  90 ++++-------------------
 drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c    |  23 +++---
 drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c |  22 +++---
 6 files changed, 102 insertions(+), 150 deletions(-)

-- 
2.5.0

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#1339009

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On Thu, Feb 18, 2016 at 05:53:05PM +0200, Daniel Baluta wrote:
> Sending this as an RFC because I don't know if style fixes are appropriate
> for this driver and also not sure if deadlock fix is the best solution.
> 
> I2C people should only look at patches 8/9 and 9/9.
> 
> The mpu6050 accel+gyro combo has an auxiliary I2C bus, allowing for
> an auxiliary sensor to be connected (eg. a magnetometer).
> 
> The mpu can either act as an I2C master (functionality not currently
> implemented in the driver) or it can use a bypass multiplexer which
> directly connects the auxiliary I2C bus pins to the main I2C bus pins [1]
> Currently the driver implements the bypass mode via an I2C mux.
> 
> This patchset fixes a deadlock in inv-mpu6050 IMU which happens when
> magnetometer (on auxiliary I2C bus) runs in parallel with accel or gyro.
> 
> First 7 patches do some cleanup in order to make INV MPU6050 code easier
> to read.
> 
> Patch number 8 allows passing NULL select callbacks to i2c_mux_master_xfer
> and i2c_mux_smbus_xfer.
> 
> Patch number 9 actually fixes the deadlock.

We recently had a bigger patch series fixing locking problems related to
muxes. I sadly didn't have the time to review it. Can you have a look if
it helps your case?

http://thread.gmane.org/gmane.linux.drivers.i2c/26169

Thanks,

   Wolfram

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#1339299

On Mon, Feb 22, 2016 at 1:17 AM, Wolfram Sang <wsa@the-dreams.de> wrote:
> On Thu, Feb 18, 2016 at 05:53:05PM +0200, Daniel Baluta wrote:
>> Sending this as an RFC because I don't know if style fixes are appropriate
>> for this driver and also not sure if deadlock fix is the best solution.
>>
>> I2C people should only look at patches 8/9 and 9/9.
>>
>> The mpu6050 accel+gyro combo has an auxiliary I2C bus, allowing for
>> an auxiliary sensor to be connected (eg. a magnetometer).
>>
>> The mpu can either act as an I2C master (functionality not currently
>> implemented in the driver) or it can use a bypass multiplexer which
>> directly connects the auxiliary I2C bus pins to the main I2C bus pins [1]
>> Currently the driver implements the bypass mode via an I2C mux.
>>
>> This patchset fixes a deadlock in inv-mpu6050 IMU which happens when
>> magnetometer (on auxiliary I2C bus) runs in parallel with accel or gyro.
>>
>> First 7 patches do some cleanup in order to make INV MPU6050 code easier
>> to read.
>>
>> Patch number 8 allows passing NULL select callbacks to i2c_mux_master_xfer
>> and i2c_mux_smbus_xfer.
>>
>> Patch number 9 actually fixes the deadlock.
>
> We recently had a bigger patch series fixing locking problems related to
> muxes. I sadly didn't have the time to review it. Can you have a look if
> it helps your case?
>
> http://thread.gmane.org/gmane.linux.drivers.i2c/26169

Thanks Wolfram,

Will look into it.

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