• Linus Walleij's avatar
    iio: st_sensors: switch to a threaded interrupt · 65925b65
    Linus Walleij authored
    commit 98ad8b41f58dff6b30713d7f09ae3834b8df7ded
    ("iio: st_sensors: verify interrupt event to status") caused
    a regression when reading ST sensors from a HRTimer trigger
    rather than the intrinsic interrupts: the HRTimer may
    trigger faster than the sensor provides new values, and
    as the check against new values available as a cause of
    the interrupt trigger was done in the poll function,
    this would bail out of the HRTimer interrupt with
    IRQ_NONE.
    
    So clearly we need to only check the new values available
    from the proper interrupt handler and not from the poll
    function, which should rather just read the raw values
    from the registers, put them into the buffer and be happy.
    
    To achieve this: switch the ST Sensors over to using a true
    threaded interrupt handler.
    
    In the interrupt thread, check if new values are available,
    else yield to the (potential) next device on the same
    interrupt line to check the registers. If the interrupt
    was ours, proceed to poll the values.
    
    Instead of relying on iio_trigger_generic_data_rdy_poll() as
    a top half to wake up the thread that polls the sensor for
    new data, have the thread call iio_trigger_poll_chained()
    after determining that is is the proper source of the
    interrupt. This is modelled on drivers/iio/accel/mma8452.c
    which is already using a properly threaded interrupt handler.
    
    In order to get the same precision in timestamps as
    previously, where samples would be timestamped in the
    poll function pf->timestamp when calling
    iio_trigger_generic_data_rdy_poll() we introduce a
    local timestamp in the sensor data, set it in the top half
    (fastpath) of the interrupt handler and provide that to the
    core when calling iio_push_to_buffers_with_timestamp().
    
    Additionally: if the active scanmask is not set for the
    sensor no IRQs should be enabled and we need to bail out
    with IRQ_NONE. This can happen if spurious IRQs fire when
    installing the threaded interrupt handler.
    
    Tested with hard interrupt triggers on LIS331DL, then also
    tested with hrtimers on the same sensor by creating a 75Hz
    HRTimer and using it to poll the sensor.
    Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    Cc: Giuseppe Barba <giuseppe.barba@st.com>
    Cc: Denis Ciocca <denis.ciocca@st.com>
    Reported-by: default avatarCrestez Dan Leonard <cdleonard@gmail.com>
    Tested-by: default avatarCrestez Dan Leonard <cdleonard@gmail.com>
    Tested-by: default avatarJonathan Cameron <jic23@kernel.org>
    Fixes: 97865fe4 ("iio: st_sensors: verify interrupt event to status")
    Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
    65925b65
st_accel_core.c 24.3 KB