On Mon, 2 Nov 2020 19:59:46 +0100
Lorenzo Bianconi <lorenzo@xxxxxxxxxx> wrote:
> If the device is configured to trigger edge interrupts it is possible to
> miss samples since the sensor can generate an interrupt while the driver
> is still processing the previous one but it has already read the fifo
> status register. Poll FIFO status register to check if there is any pending
> interrupt to process.
>
> Fixes: 89ca88a7cdf2 ("iio: imu: st_lsm6dsx: support active-low interrupts")
> Fixes: 290a6ce11d93 ("iio: imu: add support to lsm6dsx driver")
> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
Sorry, I've been a bit slow on replying to the v1 patch. Lets finish
the discussion in that thread before we move on with this.
I suspect the patch may end up the same, but the explanation may well
be different!
Jonathan
> ---
> Changes since v1:
> - add missing fixes tags
> - keep IRQF_ONESHOT even for edge-interrupts
> ---
> drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> index 5e584c6026f1..86c50136219b 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> @@ -2460,19 +2460,29 @@ st_lsm6dsx_report_motion_event(struct st_lsm6dsx_hw *hw)
> static irqreturn_t st_lsm6dsx_handler_thread(int irq, void *private)
> {
> struct st_lsm6dsx_hw *hw = private;
> + int fifo_len = 0, len;
> bool event;
> - int count;
>
> event = st_lsm6dsx_report_motion_event(hw);
>
> if (!hw->settings->fifo_ops.read_fifo)
> return event ? IRQ_HANDLED : IRQ_NONE;
>
> - mutex_lock(&hw->fifo_lock);
> - count = hw->settings->fifo_ops.read_fifo(hw);
> - mutex_unlock(&hw->fifo_lock);
> + /*
> + * If we are using edge IRQs, new samples can arrive while
> + * processing current IRQ and those may be missed unless we
> + * pick them here, so let's try read FIFO status again
> + */
> + do {
> + mutex_lock(&hw->fifo_lock);
> + len = hw->settings->fifo_ops.read_fifo(hw);
> + mutex_unlock(&hw->fifo_lock);
> +
> + if (len > 0)
> + fifo_len += len;
> + } while (len > 0);
>
> - return count || event ? IRQ_HANDLED : IRQ_NONE;
> + return fifo_len || event ? IRQ_HANDLED : IRQ_NONE;
> }
>
> static int st_lsm6dsx_irq_setup(struct st_lsm6dsx_hw *hw)
