usb: typec: ucsi: Work around PPM losing change information

commit 217504a0

 upstream.

Some/many PPMs are simply clearing the change bitfield when a
notification on a port is acknowledge. Unfortunately, doing so means
that any changes between the GET_CONNECTOR_STATUS and ACK_CC_CI commands
is simply lost.

Work around this by re-fetching the connector status afterwards. We can
then infer any changes that we see have happened but that may not be
respresented in the change bitfield.

We end up with the following actions:
 1. UCSI_GET_CONNECTOR_STATUS, store result, update unprocessed_changes
 2. UCSI_GET_CAM_SUPPORTED, discard result
 3. ACK connector change
 4. UCSI_GET_CONNECTOR_STATUS, store result
 5. Infere lost changes by comparing UCSI_GET_CONNECTOR_STATUS results
 6. If PPM reported a new change, then restart in order to ACK
 7. Process everything as usual.

The worker is also changed to re-schedule itself if a new change
notification happened while it was running.

Doing this fixes quite commonly occurring issues where e.g. the UCSI
power supply would remain online even thought the ThunderBolt cable was
unplugged.

Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Benjamin Berg <bberg@redhat.com>
Link: https://lore.kernel.org/r/20201009144047.505957-3-benjamin@sipsolutions.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>