linux-kernel - Re: IIO timestamp get skewed when suspending (st

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Message-ID: <fbef0ac8-e313-c20c-9300-9dee00588102@geanix.com>
Date:   Mon, 8 Jun 2020 14:20:40 +0200
From:   Sean Nyekjaer <sean@...nix.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     linux-iio <linux-iio@...r.kernel.org>
Subject: Re: IIO timestamp get skewed when suspending (st_lsm6dsx)

Hi Thomas,

I have a question regarding CLOCK_REALTIME and CLOCK_BOOTTIME when 
resuming from suspend.

We have run into problems with 
drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c + the first patch from 
Lorenzo Bianconi in this thread.
The accelerometer have an internal FIFO that includes a timestamp. When 
we resume from suspend,
the driver resets the fifo ts counter and sets an internal reference to 
that time.
But to me it looks like both CLOCK_REALTIME and CLOCK_BOOTIME aren't 
ready when st_lsm6dsx_resume() is called.

If this is a limitation, can you point to other drivers that have been 
able to workaround it?
Or can we wait for a flag or similar?

Best regards,
Sean Nyekjaer