linux-kernel - Re: [PATCH v5 1/3] usb: typec: tcpm: Add callbacks to mitigate wakeups due to contaminant

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Date:   Thu, 8 Dec 2022 08:03:47 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kyle Tso <kyletso@...gle.com>
Subject: Re: [PATCH v5 1/3] usb: typec: tcpm: Add callbacks to mitigate
 wakeups due to contaminant

On Wed, Dec 07, 2022 at 06:00:41PM -0800, Badhri Jagan Sridharan wrote:
> On some of the TCPC implementations, when the Type-C port is exposed
> to contaminants, such as water, TCPC stops toggling while reporting OPEN
> either by the time TCPM reads CC pin status or during CC debounce
> window. This causes TCPM to be stuck in TOGGLING state. If TCPM is made
> to restart toggling, the behavior recurs causing redundant CPU wakeups
> till the USB-C port is free of contaminant.
> 
> [206199.287817] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [206199.640337] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [206199.985789] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> ...
> 
> TCPM invokes is_potential_contaminant callback to allow low level chip
> drivers to monitor TCPM state machine transitions and notify TCPM when
> the Type-C port needs to be checked for potential contaminant presence.
> TCPCs which do have the needed hardware can implement the check_contaminant
> callback which is invoked by TCPM to evaluate for presence of contaminant.
> Lower level TCPC driver can restart toggling through TCPM_PORT_CLEAN event
> when the driver detects that USB-C port is free of contaminant.
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> Change-Id: I136d788bb46d871d12e64bd73fd50a77b4659dbf
> ---

Always run checkpatch.pl on your patches so you don't get a grumpy
maintainer asking why you didn't run checkpatch.pl on your patches :(