hwmon: (ucd90320) Add minimum delay between bus accesses
authorLars-Peter Clausen <lars@metafoo.de>
Sun, 12 Mar 2023 16:03:12 +0000 (09:03 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 22 Mar 2023 12:33:52 +0000 (13:33 +0100)
commit634b3304f78d3cdc724fb7811dc42f540d3d6442
treebd40d3dfad7c65c9e4866b04a464cd8cf849840b
parent265656c43eb9e256d15ee594fd9dbcb88cee1b75
hwmon: (ucd90320) Add minimum delay between bus accesses

[ Upstream commit 8d655e65237643c48ada2c131b83679bf1105373 ]

When probing the ucd90320 access to some of the registers randomly fails.
Sometimes it NACKs a transfer, sometimes it returns just random data and
the PEC check fails.

Experimentation shows that this seems to be triggered by a register access
directly back to back with a previous register write. Experimentation also
shows that inserting a small delay after register writes makes the issue go
away.

Use a similar solution to what the max15301 driver does to solve the same
problem. Create a custom set of bus read and write functions that make sure
that the delay is added.

Fixes: a470f11c5ba2 ("hwmon: (pmbus/ucd9000) Add support for UCD90320 Power Sequencer")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20230312160312.2227405-1-lars@metafoo.de
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
drivers/hwmon/pmbus/ucd9000.c