Re: [PATCH RFC 1/2] usb: dwc3: Let the glue keep the host bus suspended across suspend-to-idle

[sashiko-bot@kernel.org]

> From: Arun Iyengar <aiyengar1990@gmail.com>
> 
> In host mode, dwc3_suspend_common() tears the core down for system
> suspend (dwc3_core_exit(): PHYs off, core reset) unless the controller
> is a wakeup source. By then xhci-plat has already suspended the bus:
> the root ports and every device behind them are in U3/suspend and
> expect to keep their power session (Documentation/driver-api/usb/
> persist.rst). Resetting the core ends all of them. On resume xhci-plat
> finds a reset controller ("root hub lost power or was reset") and the
> USB core has to reset-resume every device, which only works for devices
> that come back within the 2 s that usb_port_resume() waits for a
> connection.
> 
> Devices that are cut off in U3 do not necessarily come back that fast.
> On an Orange Pi 5 (RK3588S) a SanDisk Extreme drive on the Type-A USB3
> [ ... ]
> exactly when suspend tore it down, which xhci_power_lost now records.
> Nothing changes for platforms that do not set the flag, nor for
> suspend-to-RAM, hibernation and needs_full_reinit controllers.
> 
> Signed-off-by: Arun Iyengar <aiyengar1990@gmail.com>

Sashiko has reviewed this patch and found no issues.

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