From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
To: Joonhoe Kim <26rote@gmail.com>, vkoul@kernel.org
Cc: neil.armstrong@linaro.org, mani@kernel.org,
dmitry.baryshkov@oss.qualcomm.com, val@packett.cool,
wesley.cheng@oss.qualcomm.com, linux-arm-msm@vger.kernel.org,
linux-phy@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] phy: qcom: qmp-combo: Leave the USB PCS alone in DP-only mode
Date: Mon, 2 Nov 2026 14:34:18 +0100 [thread overview]
Message-ID: <6cd9240d-5628-4c35-b7ca-bbbae7f62fe9@oss.qualcomm.com> (raw)
In-Reply-To: <20261023123512.1912-1-26rote@gmail.com>
On 10/23/26 2:35 PM, Joonhoe Kim wrote:
> In DP-only mode (DisplayPort pin assignments C and E) all four lanes
> belong to the DisplayPort PHY and the USB PCS stays powered down.
> Three paths still touch the USB PCS in this state:
>
> - The USB controller can exit and re-init its PHY in DP-only mode, e.g.
> across a system suspend that loses power. qmp_combo_usb_init() then
> programs the USB serdes, lane and PCS tables over the DisplayPort
> configuration and times out waiting for PHYSTATUS, and
> qmp_combo_usb_exit() resets and powers down a PCS that is not in use.
> - qmp_combo_typec_switch_set() powers the USB PCS off and on when the
> orientation changes in DP-only mode, e.g. when a DP-only sink is
> plugged in the other way round while the mux is still in DP-only
> mode.
> - qmp_combo_reconfigure_phy() powers the USB PCS off again when the
> port leaves DP-only mode.
>
> Skip the USB PCS in these paths in DP-only mode. Keep the
> qmp_combo_com_init()/qmp_combo_com_exit() reference and usb_init_count,
> so that qmp_combo_reconfigure_phy() powers the USB PCS up when the port
> leaves DP-only mode.
>
> On a Lenovo Y700 Gen 5 (TB323FU, Kaanapali) with a USB-C monitor
> in pin assignment C, resume from s2idle fails with "phy initialization
> timed-out", the dwc3 resume returns -110 and the following xHCI resume
> hangs the system.
This sounds like a gap in the DWC3 driver, we should bail out of r/w
any registers if resume failed
Konrad
prev parent reply other threads:[~2026-11-02 13:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-23 12:35 Joonhoe Kim
2026-10-27 11:20 ` Abel Vesa
2026-11-01 11:06 ` Manivannan Sadhasivam
2026-11-02 13:32 ` Konrad Dybcio
2026-11-02 13:34 ` Konrad Dybcio [this message]
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