Re: [PATCH v4 2/6] iio: accel: mma8452: Optimize struct mm8452_data member orders

[Esben Haabendal]

"Jonathan Cameron" <jic23@xxxxxxxxxx> writes:

> On Wed, 12 Aug 2026 16:30:33 +0200
> Esben Haabendal <esben@xxxxxxxxxx> wrote:
>
>> Reorder struct mma8452_data members to avoid holes.
> Trivial but sashiko pointed out mm[a]_8452 in the title.
> I'll tidy that up if nothing significant comes up.
>
> Interestingly Sashiko also thinks it found a deadlock.
> Given you are working with this driver if you have time could
> you take a look at that.
>
> https://sashiko.dev/#/patchset/20260812-mma8452-open-drain-v4-0-bfca15d02b59%40geanix.com
>
> I'm rather surprised to see the lock taken in the runtime
> pm suspend callback. It is probably there to close a race
> where the device is being suspended and the sampling
> frequency is being written.  I'm not immediately sure what
> the best way to fix it is. One thing that would work is to
> do pm_runtime_get* to raise the reference counter and stop
> there being any chance of an autosuspend.

The mma8452_change_config() function is grabbing &data->lock, and is
forcing chip in stand mode while applying change. This needs to be
synchronized with mma8452_runtime_suspend() switching to standby mode,
to avoid a race condition where mma8452_change_config() would end up
undoing the change made by runtime PM, due to it keeping the old state
in is_active local variable. So far it makes sense.

But I don't see the reason for mma8452_read_raw(IIO_CHAN_INFO_RAW)
grabbing the lock for the call to mma8452_read(). And when
mma8452_trigger_handler() calls mma8452_read() it does so without
data->lock held.

So maybe we we can simply drop the &data->lock from mma8452_read_raw()?

/Esben