Re: IIO timestamp get skewed when suspending (st_lsm6dsx)

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> Hi,

Hi Sean,

> 
> I don't know if it's normal behavior or maybe just a problem related to the
> buffered reads in st_lsm6dsx.
> 
> But when we have the buffered reads enabled and suspending for x amount of
> time. The iio timestamps is, x amount of time is delayed. As seen here:
> 
> https://gist.github.com/sknsean/60e20c2fa3a3c6d69ef128c703ed43fc
> 
> From your own software (but I'm able to reproduce with libiio/iio_readdev)
> 
> First col is system time,
> Second timestamp is the iio timestamp
> 
> Could a solution, be to call st_lsm6dsx_reset_hw_ts() in st_lsm6dsx_resume()
> ?

yes, I think so. Could you please try to patch below? Thanks.

Regards,
Lorenzo

> 
> /Sean

From f4ea9019d3b6fb1ad80747cf378bf1fbdebd3dd8 Mon Sep 17 00:00:00 2001
Message-Id: <f4ea9019d3b6fb1ad80747cf378bf1fbdebd3dd8.1590699935.git.lorenzo@kernel.org>
From: Lorenzo Bianconi <lorenzo@kernel.org>
Date: Thu, 28 May 2020 23:05:16 +0200
Subject: [PATCH] iio: imu: st_lsm6dsx: reset hw ts after resume

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h       |  3 +--
 .../iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c    | 23 ++++++++++++-------
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c  |  2 +-
 3 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
index b56df409ed0f..529970195b39 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
@@ -436,8 +436,7 @@ int st_lsm6dsx_update_watermark(struct st_lsm6dsx_sensor *sensor,
 				u16 watermark);
 int st_lsm6dsx_update_fifo(struct st_lsm6dsx_sensor *sensor, bool enable);
 int st_lsm6dsx_flush_fifo(struct st_lsm6dsx_hw *hw);
-int st_lsm6dsx_set_fifo_mode(struct st_lsm6dsx_hw *hw,
-			     enum st_lsm6dsx_fifo_mode fifo_mode);
+int st_lsm6dsx_resume_fifo(struct st_lsm6dsx_hw *hw);
 int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw);
 int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw);
 int st_lsm6dsx_check_odr(struct st_lsm6dsx_sensor *sensor, u32 odr, u8 *val);
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
index afd00daeefb2..7de10bd636ea 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
@@ -184,8 +184,8 @@ static int st_lsm6dsx_update_decimators(struct st_lsm6dsx_hw *hw)
 	return err;
 }
 
-int st_lsm6dsx_set_fifo_mode(struct st_lsm6dsx_hw *hw,
-			     enum st_lsm6dsx_fifo_mode fifo_mode)
+static int st_lsm6dsx_set_fifo_mode(struct st_lsm6dsx_hw *hw,
+				    enum st_lsm6dsx_fifo_mode fifo_mode)
 {
 	unsigned int data;
 
@@ -302,6 +302,18 @@ static int st_lsm6dsx_reset_hw_ts(struct st_lsm6dsx_hw *hw)
 	return 0;
 }
 
+int st_lsm6dsx_resume_fifo(struct st_lsm6dsx_hw *hw)
+{
+	int err;
+
+	/* reset hw ts counter */
+	err = st_lsm6dsx_reset_hw_ts(hw);
+	if (err < 0)
+		return err;
+
+	return st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
+}
+
 /*
  * Set max bulk read to ST_LSM6DSX_MAX_WORD_LEN/ST_LSM6DSX_MAX_TAGGED_WORD_LEN
  * in order to avoid a kmalloc for each bus access
@@ -675,12 +687,7 @@ int st_lsm6dsx_update_fifo(struct st_lsm6dsx_sensor *sensor, bool enable)
 		goto out;
 
 	if (fifo_mask) {
-		/* reset hw ts counter */
-		err = st_lsm6dsx_reset_hw_ts(hw);
-		if (err < 0)
-			goto out;
-
-		err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
+		err = st_lsm6dsx_resume_fifo(hw);
 		if (err < 0)
 			goto out;
 	}
diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
index 0b776cb91928..b3a08e3e2359 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
@@ -2458,7 +2458,7 @@ static int __maybe_unused st_lsm6dsx_resume(struct device *dev)
 	}
 
 	if (hw->fifo_mask)
-		err = st_lsm6dsx_set_fifo_mode(hw, ST_LSM6DSX_FIFO_CONT);
+		err = st_lsm6dsx_resume_fifo(hw);
 
 	return err;
 }
-- 
2.26.2


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