Re: [PATCH] i2c: s3c2410: remove superfluous runtime PM calls

On Wed, Dec 16, 2015 at 02:53:07PM +0100, Sylwester Nawrocki wrote:

On 15/12/15 19:14, Wolfram Sang wrote:

quoted

Since commit 6ada5c1e1b077a ("i2c: Mark adapter devices with
pm_runtime_no_callbacks"), runtime PM on adapters turned into a no-op.
So, we can remove these calls.

Won't this break i2c client devices that use runtime PM? Not sure
if any cases of such client exist now, I'll try to find some time
to test this change.

Our CODECs can be controlled over I2C and use runtime PM.
However, this change doesn't seem to have any adverse effect on
them that I can find.

Tested-by: Charles Keepax <redacted>

IIRC client's pm_runtime* calls return error if their parent device's
runtime PM is not enabled. Also enabling runtime PM on the i2c adapter
allows propagating runtime PM calls up to its parent - the i2c
controller platform device.

So perhaps in your patch we should only remove pm_runtime_get_sync,
pm_runtime_put calls, leaving runtime PM on the adapter enabled.
For any future cases where the Exynos I2C controller is not in an
always on power domain the runtime PM handling in this driver would
need to be further reworked anyway.

Perhaps we could just enable/disable adapter's runtime PM in i2c core.

Afraid not sure I can comment on this part.

Thanks,
Charles