Re: [PATCH 0/5] Fix various races in UCSI

Heikki Krogerus
2024-03-22T10:03:03Z

On Wed, Mar 20, 2024 at 08:39:21AM +0100, Christian A. Ehrhardt wrote:
> 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.

That sounds good to me.

thanks,

--
heikki