Opened 2 years ago
serial console for EHCI debug port
|Reported by:||pulkomandy||Owned by:||mmlr|
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).
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.