linux-kernel - Re: [PATCH] usb: typec: tpcm: Fix issues with power being removed during reset

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Message-ID: <3a09ea3b-3a42-4fce-85f8-f8408a4a2206@sirena.org.uk>
Date: Tue, 13 Feb 2024 13:13:41 +0000
From: Mark Brown <broonie@...nel.org>
To: Badhri Jagan Sridharan <badhri@...gle.com>
Cc: Guenter Roeck <linux@...ck-us.net>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Gábor Stefanik <netrolller.3d@...il.com>,
	rdbabiera@...gle.com, amitsd@...gle.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: tpcm: Fix issues with power being removed
 during reset

On Tue, Feb 13, 2024 at 02:09:16AM -0800, Badhri Jagan Sridharan wrote:
> Hi Mark,

Please don't top post, reply in line with needed context.  This allows
readers to readily follow the flow of conversation and understand what
you are talking about and also helps ensure that everything in the
discussion is being addressed.

> While HI-Zing CC pins disrupts power for batteryless devices, not
> Hi-Zing CC pins would prevent clean error recovery for self powered
> devices which is why "usb: typec: tcpm: fix cc role at port reset" was reverted.
> Please note that the breakage in error recovery behavior is a
> regression as well.
> Hi-Zing CC pins would make the port partner recognize it as disconnect
> and will result in bringup the connection back cleanly.
> 
> How about leveraging "self-powered" device tree property and Hi-Zing
> CC pins only when using "self-powered" ?
> This should help devices which don't have batteries while NOT regressing
> the error recovery behavior for the self powered devices.

I don't super care so long as the boards I care about continue to
function, I submitted this patch because the only response to my report
about the rk3399-roc-pc having been broken in mainline was a
confirmation that the failure was expected.  As I noted in the commit
log checking if there is an alternative power source does seem like a
viable option here, I am not particularly familiar with this code.

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