Re: [PATCH v2 0/2] iio: magnetometer: fix the register restore on resume in mmc35240 and mmc5633

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 12 Oct 2026 10:30:53 +0530
Shashank Mohan Jain <jain.sm@gmail.com> wrote:

> The resume callbacks of mmc35240 and mmc5633 call
> regcache_sync_region() before they take the regmap out of cache-only
> mode. Since v7.3-rc1 regmap refuses a sync in cache-only mode with a
> WARN and -EINVAL (86fc3483a4d6 and afc8e3ee8307), so both drivers now
> warn on every resume and no longer restore their control registers.
> 
> The kernel-doc added by 86fc3483a4d6 says that the caller has to
> disable cache-only mode before the sync, so the two patches change the
> order in the drivers.
> 
> The Fixes tags name the commit that added each resume callback
> (553a776b7908 for mmc35240, 6e5f6bf2e3f0 for mmc5633), as suggested by
> Bui Duc Phuc in review of v1: the wrong order predates the regcache
> change (86fc3483a4d6 / afc8e3ee8307), which only turned it into a WARN
> and a failed restore.
> 
> I have no hardware for either chip. The patches were tested in qemu
> with the drivers bound to an i2c-stub device and a suspend/resume
> cycle through /sys/power/pm_test; the details are in the changelogs.
> A scan of drivers/ and sound/ for other resume paths which sync before
> leaving cache-only mode in the same function found only these two.
> 
> Based on mainline (a5ebb76233b7, v7.3-rc6+); the patches also apply
> to next-20261009.
Applied both to the fixes-togreg branch of iio.git and marked them
for stable.  Seems harmless if they get backported further than
the change that added the error.

Jonathan

> 
> Changes since v1:
>  - repoint the Fixes tags to the commits that added the resume
>    callbacks (553a776b7908, 6e5f6bf2e3f0), per Bui Duc Phuc's review;
>    the code change is unchanged.
>  - note in each changelog that the ordering predates the regcache
>    change that exposed it.
> 
> Shashank Mohan Jain (2):
>   iio: magnetometer: mmc35240: leave cache-only mode before the cache
>     sync
>   iio: magnetometer: mmc5633: leave cache-only mode before the cache
>     sync
> 
>  drivers/iio/magnetometer/mmc35240.c | 3 +--
>  drivers/iio/magnetometer/mmc5633.c  | 3 +--
>  2 files changed, 2 insertions(+), 4 deletions(-)
> 
> 
> base-commit: a5ebb76233b79db01e82e061173cb73c6d2b5c6b