[PATCH v2 0/3] usb: dwc3: qcom: Keep USB 2.0 working in DisplayPort-only modes

[Joonhoe Kim <26rote@gmail.com>]

With a USB-C monitor in DisplayPort pin assignment C or E, the QMP
USB3-DP combo PHY gives all four lanes to DisplayPort and keeps its USB
PCS powered down. The USB 2.0 pair still works. Such monitors often
have a USB 2.0 hub. But the dwc3 controller still depends on the USB3
PIPE clock. On Kaanapali the next xHCI reset in this state times out
("Host halt failed, -110"). USB stays lost until the cable is replugged.
Commit f546912bcac6 ("phy: qcom: qmp-combo: Move pipe_clk on/off to
common") keeps the pipe clock branch enabled. That is not enough here.

This series lets the controller be a Type-C mode switch next to the PHY
and moves it to the UTMI clock, the way "qcom,select-utmi-as-pipe-clk"
does statically, before the PHY switches to DP-only mode.

On Kaanapali the PHY becomes a mode switch with Balaji Kalkonda's
DisplayPort series [1]; patch 3 is the controller side for the same
SoC. Other SoCs whose PHY is already a mode switch (e.g. SM8650,
SM8750) may need the same property on their controller node (not
tested).

Related fixes sent separately: "phy: qcom: qmp-combo: Leave the USB PCS
alone in DP-only mode" (suspend in DP-only mode) [2] and "usb: typec:
mux: fsa4480: Keep the USB 2.0 switch on in DP-only modes" (boards with
an FSA4480 on the USB 2.0 pair) [3].

Patch 2 conflicts with Vladyslav Tymoshchuk's "usb: dwc3: qcom: Defer
VBUS override update during system suspend" [4] in
dwc3_qcom_pm_suspend() and dwc3_qcom_pm_resume(). Both add a lock
there. Like [4], the mux callback defers the QSCRATCH write while the
glue is suspended for system sleep. On top of [4] the two locks can
become one.

Patches 1-2 are for the USB tree. Patch 3 must not be applied before
patch 2: with "mode-switch" on the controller and no mux registered by
dwc3-qcom, pmic_glink_altmode defers its probe indefinitely.

Tested on a Lenovo Y700 Gen 5 (TB323FU, Kaanapali) with the series
backported to v7.3, plus [2] and [3]. A USB-C monitor ran over 4-lane
HBR3. Its USB 2.0 hub worked after 10 replugs and after a plug-in during
s2idle. In the s2idle case the mux state came after resume, so the
deferred clock switch was not exercised. With the monitor
unplugged, a USB 3 stick enumerated at SuperSpeed. Quick replugs (under
a second) worked 9 times out of 10. The other time no PD contract was
made, so no alternate mode was entered.

Changes in v2:
- Patch 1: use the common usb-switch schema
- Patch 2: switch back to the PIPE clock in the mux callback, when a
  USB state follows the safe state. v1 waited for the next role change,
  which can come before the mux state (Sashiko)
- Patch 2: keep the UTMI clock on a change of pin assignment while
  DisplayPort is active, as the PHY keeps its mode then
- Patch 2: while the glue is suspended for system sleep, only record
  the mux state and select the clock on resume
- Patch 2: depend on TYPEC || TYPEC=n. Skip the mux without
  CONFIG_TYPEC. The arm64 defconfig has USB_DWC3_QCOM=y and TYPEC=m,
  which failed to link (Sashiko). It now builds the glue as a module
- Patch 2: no change to the role notifier
- Patch 3: note the dependency on [1] for the PHY's "mode-switch"
- Patch 3: add Reviewed-by from Abel
- Link to v1: https://lore.kernel.org/all/20261102215121.738-1-26rote@gmail.com/

[1] https://lore.kernel.org/all/20261022-kaanapali_dp-v3-0-b5ae8e6083c3@oss.qualcomm.com/
[2] https://lore.kernel.org/all/20261023123512.1912-1-26rote@gmail.com/
[3] https://lore.kernel.org/all/20261022165143.1327-1-26rote@gmail.com/
[4] https://lore.kernel.org/all/20261018143126.3978-1-tvlad744@gmail.com/

Joonhoe Kim (3):
  dt-bindings: usb: qcom,snps-dwc3: Add mode-switch
  usb: dwc3: qcom: Use the UTMI clock as PIPE clock in DisplayPort-only
    modes
  arm64: dts: qcom: kaanapali: Mark the USB controller as a Type-C mode
    switch

 .../bindings/usb/qcom,snps-dwc3.yaml          |   3 +
 arch/arm64/boot/dts/qcom/kaanapali.dtsi       |   1 +
 drivers/usb/dwc3/Kconfig                      |   1 +
 drivers/usb/dwc3/dwc3-qcom.c                  | 103 +++++++++++++++---
 4 files changed, 95 insertions(+), 13 deletions(-)


base-commit: 7649ba73f9e7e1e04d0b46213e39c79ae09dd55c
-- 
2.43.0