>From 98d9a672f7da10abf7bb3cb36ec5dc755cf6a70d Mon Sep 17 00:00:00 2001 From: Lorenzo Bianconi Date: Sat, 14 Nov 2020 19:39:05 +0100 Subject: [PATCH 2/2] iio: imu: st_lsm6dsx: fix edge-trigger interrupts commit 3f9bce7a22a3f8ac9d885c9d75bc45569f24ac8b upstream If we are using edge IRQs, new samples can arrive while processing current interrupt since there are no hw guarantees the irq line stays "low" long enough to properly detect the new interrupt. In this case the new sample will be missed. Polling FIFO status register in st_lsm6dsx_handler_thread routine allow us to read new samples even if the interrupt arrives while processing previous data and the timeslot where the line is "low" is too short to be properly detected. Fixes: 89ca88a7cdf2 ("iio: imu: st_lsm6dsx: support active-low interrupts") Fixes: 290a6ce11d93 ("iio: imu: add support to lsm6dsx driver") Signed-off-by: Lorenzo Bianconi Link: https://lore.kernel.org/r/5e93cda7dc1e665f5685c53ad8e9ea71dbae782d.1605378871.git.lorenzo@kernel.org Cc: Signed-off-by: Jonathan Cameron [sudip: manual backport to old irq handler path] Signed-off-by: Sudip Mukherjee --- drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c index 8974d7ba657b..4d89de0be58b 100644 --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c @@ -475,13 +475,29 @@ static irqreturn_t st_lsm6dsx_handler_irq(int irq, void *private) static irqreturn_t st_lsm6dsx_handler_thread(int irq, void *private) { struct st_lsm6dsx_hw *hw = private; - int count; + int fifo_len = 0, len; - mutex_lock(&hw->fifo_lock); - count = st_lsm6dsx_read_fifo(hw); - mutex_unlock(&hw->fifo_lock); + /* + * If we are using edge IRQs, new samples can arrive while + * processing current interrupt since there are no hw + * guarantees the irq line stays "low" long enough to properly + * detect the new interrupt. In this case the new sample will + * be missed. + * Polling FIFO status register allow us to read new + * samples even if the interrupt arrives while processing + * previous data and the timeslot where the line is "low" is + * too short to be properly detected. + */ + do { + mutex_lock(&hw->fifo_lock); + len = st_lsm6dsx_read_fifo(hw); + mutex_unlock(&hw->fifo_lock); + + if (len > 0) + fifo_len += len; + } while (len > 0); - return count ? IRQ_HANDLED : IRQ_NONE; + return fifo_len ? IRQ_HANDLED : IRQ_NONE; } static int st_lsm6dsx_buffer_preenable(struct iio_dev *iio_dev) -- 2.11.0