Re: [PATCH 2/2] usb: dwc3: Keep the host bus suspended, not torn down, across suspend-to-idle

[Vlad <tvlad744@gmail.com>]

From: Vladyslav Tymoshchuk <tvlad744@gmail.com>

On Tue, Nov 10, 2026 at 07:16:44AM +0000, Arun Iyengar wrote:
> Suspend-to-idle does not power anything down behind the drivers'
> back, so there is no reason to end the power sessions there. Keep the
> core, its PHYs and the suspended ports, as is already done for wakeup,
> and mark the device as being on the awake path so that a power domain
> with GENPD_FLAG_ACTIVE_WAKEUP stays on as well.

A data point from a Qualcomm board where the first sentence does not
hold. I have not run this series; what follows is the existing "kept
for wakeup" path, which this patch extends to every suspend-to-idle.

On SM8750 (OnePlus Pad 3, v7.3-rc5 plus board patches) the controller
node is a wakeup source, so dwc3 keeps the core in host mode. The USB
GDSCs are PWRSTS_OFF_ON in gcc-sm8750 and the qcom GDSC driver does not
set GENPD_FLAG_ACTIVE_WAKEUP, so genpd powers them off in s2idle all
the same. With a USB stick on the port the xHCI then comes back like
this, in 3 of 3 cycles of 150 s:

  arm-smmu 15000000.iommu: Unhandled context fault: fsr=0x402, iova=0x669fd3200, fsynr=0x370011, cbfrsynra=0x40, cb=5
  xhci-hcd xhci-hcd.3.auto: WARNING: Host System Error
  xhci-hcd xhci-hcd.3.auto: xHCI host not responding to stop endpoint command
  xhci-hcd xhci-hcd.3.auto: xHCI host controller not responding, assume dead
  xhci-hcd xhci-hcd.3.auto: HC died; cleaning up

With the GDSCs in retention [1], as SM8650 and X1E80100 have them, the
same 150 s cycle passed 5 of 5 times, and two shorter cycles of 25 s
passed as well.

This is the third point of the Sashiko review seen on hardware:
device_set_awake_path() does nothing for a domain without the flag,
and the core is treated as kept although its power went away. I would
expect 2/2 to bring this failure to SM8750 controllers with wakeup
disabled too, unless [1] is applied.

[1] https://lore.kernel.org/all/20261110213346.1359-1-tvlad744@gmail.com/