Re: [PATCH] usb: ehci: skip companion handoff when no companion exists

[sashiko-bot@kernel.org]

> EHCI controllers without an integrated root-hub transaction translator
> unconditionally set PORT_OWNER whenever a root port sees low-speed line
> state before reset, finishes reset without enabling High-Speed mode, or
> is relinquished by usbcore after enumeration fails. When no companion
> controller is present or enabled, setting PORT_OWNER routes the port
> away from EHCI to a nonexistent or disabled controller. A single missed
> High-Speed chirp or transient D+/D- bounce during reset then strands
> downstream USB 2.0 hubs until EHCI is rebound, and connecting a USB 1.1
> device leaves the port dead to later USB 2.0 devices.
> 
> Check during ehci_setup() whether HCSPARAMS reports zero companions
> (HCS_N_CC == 0), both CONFIG_USB_OHCI_HCD and CONFIG_USB_UHCI_HCD are
> disabled in Kconfig (such as in aspeed_g4_defconfig,
> aspeed_g5_defconfig, and BMC builds without UHCI or OHCI), or a Device
> Tree companion phandle points to a disabled node. Runtime companion
> binding is intentionally not checked at setup time so modular or
> later-probing companion drivers still receive handoffs.
> 
> When no companion is available, set ehci->no_companion to skip
> PORT_OWNER handoffs and omit the companion sysfs attribute, matching
> the integrated-TT path so usbcore keeps port ownership on EHCI. USB 1.1
> full- and low-speed devices still cannot enumerate without an
> integrated TT or companion controller and will fail usbcore's normal
> reset retries instead of triggering a PORT_OWNER handoff.
> 
> Signed-off-by: William A. Kennington III <william@wkennington.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261114051653.1353346-1-william@wkennington.com?part=1