RPi4B: edk2-platforms updated because _DMA method for XHCI DMA issue insufficient for Linux; pftf/RPi4 v1.21 has the change

[Mark Millard]

Quoting https://github.com/tianocore/edk2-platforms/commit/dac891da5cf326d2b4e9aa5adab1d9320b2dd443 :

Add an IORT table that will limit XHCI DMA to 2 GB, by setting the
DMA width to 31 bits. This is needed for Linux/arm64, which can
only reliably deal with devices that are unable to perform DMA to
the entire 32-bit address range if it can discover their existence
early during boot, and this is before the ACPI interpreter is up
and running (which rules out calling the _DMA method of the XHC0
object)

End Quote

https://github.com/pftf/RPi4/releases/tag/v1.21 includes this change.
(It also updates the RPI4B firmware to quit using the broken start4.elf
that corrupted Device Tree information.)

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)