linux-kernel - Re: [PATCH v2] usb: typec: qcom-pmic-typec: split HPD bridge alloc and registration

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Date: Mon, 8 Apr 2024 09:11:32 +0200
From: Johan Hovold <johan@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Caleb Connolly <caleb.connolly@...aro.org>
Subject: Re: [PATCH v2] usb: typec: qcom-pmic-typec: split HPD bridge alloc
 and registration

On Mon, Apr 08, 2024 at 04:06:40AM +0300, Dmitry Baryshkov wrote:
> If a probe function returns -EPROBE_DEFER after creating another device
> there is a change of ending up in a probe deferral loop, (see commit
> fbc35b45f9f6 ("Add documentation on meaning of -EPROBE_DEFER").
> 
> In order to prevent such probe-defer loops caused by qcom-pmic-typec
> driver, use the API added by Johan Hovold and move HPD bridge
> registration to the end of the probe function.

You should be more specific here: which function called after
qcom_pmic_typec_probe() can trigger a probe deferral?

I doubt that applies to tcpm->port_start() and tcpm->pdphy_start() in
which case the bridge should be added before those calls unless there
are other reasons for not doing so, which then also should be mentioned.

I suspect the trouble is with tcpm_register_port(), but please spell
that out and mention in which scenarios that function may return
-EPROBE_DEFER.

Johan