Opened 11 months ago

#14844 new bug

serial console for EHCI debug port

Reported by: pulkomandy Owned by: mmlr
Priority: normal Milestone: Unscheduled
Component: Drivers/USB/EHCI Version: R1/Development
Keywords: Cc:
Blocked By: Blocking:
Has a Patch: no Platform: All

Description

I discovered that EHCI has support for a "debug port". It's a simplified protocol for sending data to a specific USB device (of which DIY versions exist).

https://www.coreboot.org/EHCI_Debug_Port

Documented in EHCI specs.

On machines/chipsets which support this, only one of the USB ports can be used for this purpose. It's a low level interface, meaning we can use it even early on in the boot process, without setting up EHCI. So our serial output could be routed there.

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