[PATCH 0/5] Fix various races in UCSI

Christian A. Ehrhardt
2024-03-20T07:48:36Z

Fix various races in UCSI code:
- The EVENT_PENDING bit should be cleared under the PPM lock to
avoid spurious re-checking of the connector status.
- The initial connector change notification during init may be
lost which can cause a stuck UCSI controller. Observed by me
and others during resume or after module reload.
- Unsupported commands must be ACKed. This was uncovered by the
recent change from Jameson Thies that did sent unsupported commands.
- The DELL quirk still isn't quite complete and I've found a more
elegant way to handle this. A connector change ack _is_ accepted
on affected systems if it is bundled with a command ack.
- If we do two consecutive resets or the controller is already
reset at boog the second reset might complete early because the
reset complete bit is already set. ucsi_ccg.c has a work around
for this but it looks like an more general issue to me.

NOTE:
As a result of these individual fixes we could think about the
question if there are additional cases where we send some type
of command to the PPM while the bit that indicates its completion
is already set in CCI. And in fact there is one more case where
this can happen: The ack command that clears the connector change
is sent directly after the ack command for the previous command.
It might be possible to simply ack the connector change along with
the first command ucsi_handle_connector_change() and not at the
end. AFAICS the connector lock should protect us from races that
might arise out of this.

Christian A. Ehrhardt (5):
usb: typec: ucsi: Clear EVENT_PENDING under PPM lock
usb: typec: ucsi: Check for notifications after init
usb: typec: ucsi: Ack unsupported commands
usb: typec: ucsi_acpi: Refactor and fix DELL quirk
usb: typec: ucsi: Clear UCSI_CCI_RESET_COMPLETE before reset

drivers/usb/typec/ucsi/ucsi.c | 56 ++++++++++++++++++++--
drivers/usb/typec/ucsi/ucsi_acpi.c | 75 +++++++++++++-----------------
2 files changed, 84 insertions(+), 47 deletions(-)

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2.40.1