linux-kernel - Re: [PATCH 2/3] usb: typec: ps883x: fix missing accessibility check

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Message-ID: <Z8VVGBDh2VnxyHw0@hovoldconsulting.com>
Date: Mon, 3 Mar 2025 08:07:04 +0100
From: Johan Hovold <johan@...nel.org>
To: Jens Glathe <jens.glathe@...schoolsolutions.biz>
Cc: Johan Hovold <johan+linaro@...nel.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Abel Vesa <abel.vesa@...aro.org>,
	Stephan Gerhold <stephan.gerhold@...aro.org>,
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] usb: typec: ps883x: fix missing accessibility check

Hi Jens,

On Sun, Mar 02, 2025 at 02:34:41PM +0100, Jens Glathe wrote:
> On 2/18/25 16:29, Johan Hovold wrote:
> > Make sure that the retimer is accessible before registering to avoid
> > having later consumer calls fail to configure it, something which, for
> > example, can lead to a hotplugged display not being recognised:
> >
> > 	[drm:msm_dp_panel_read_sink_caps [msm]] *ERROR* read dpcd failed -110
> >
> > Fixes: 257a087c8b52 ("usb: typec: Add support for Parade PS8830 Type-C Retimer")
> > Cc: Abel Vesa <abel.vesa@...aro.org>
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> 
> unfortunately, this one goes south on the HP Omnibook X14, and also on
> the Elitebook G1Q. After excluding a lot of other causes, like inverted
> resets and wrong i2c channels, I did a bisect and landed at this commit.

According to the X14 ACPI tables there is no ps8830 on &i2c7i (I2C8),
which means that the devicetree is broken.

> Looking at it, I speculatively increased the firmware initialization
> delay to 200ms. To no effect. Reverting this patch "resolves" the issue.

This patch (series) only makes sure that there actually is a retimer at
the described address so it appears to work as intended.

You may unknowingly have been relying on firmware configuration or reset
values. Does orientation switching (SuperSpeed in both orientations) and
DP altmode work at all on the second USB-C port with this patch
reverted?

Johan