Opened 5 years 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: | ||
| 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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