With the upcoming release of Windows 11, Microsoft has introduced a new USB Device-Specific Method (_DSM) function to enforce 64-bit xHCI registers to be accessed through two sequential 32-bit requests. The new function (Query controller register access type - Function 6) is documented at: https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/usb-device-specific-method---dsm-
Support for this feature is required on the raspberry Pi 4 where there is a bug/limitation in the xHCI stack that prevents full range 64-bit access from working correctly. It should be noted that an equivalent for this _DSM is not required on Linux, as 64-bit xHCI register access is already broken down into 2x32-bit by the drivers there. With this _DSM, and unlike what is the case for Windows 10, Windows 11 can now be installed on the Raspberry Pi 4 without having to alter any of the installation files, as we were able to validate using the latest Windows 11 Build 22000 Insider image. Signed-off-by: Pete Batard <p...@akeo.ie> Tested-by: Pete Batard <p...@akeo.ie> --- Platform/RaspberryPi/AcpiTables/Xhci.asl | 21 ++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/Platform/RaspberryPi/AcpiTables/Xhci.asl b/Platform/RaspberryPi/AcpiTables/Xhci.asl index 9b37277956d9..00b0cd29c69c 100644 --- a/Platform/RaspberryPi/AcpiTables/Xhci.asl +++ b/Platform/RaspberryPi/AcpiTables/Xhci.asl @@ -138,6 +138,27 @@ DefinitionBlock (__FILE__, "SSDT", 5, "RPIFDN", "RPI4XHCI", 2) Debug = "xHCI enable" Store (0x6, CMND) } + + /* + * Microsoft's USB Device-Specific Methods. See: + * https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/usb-device-specific-method---dsm- + */ + Name (DSMU, ToUUID ("ce2ee385-00e6-48cb-9f05-2edb927c4899")) + + Method (_DSM, 4, Serialized) { + If (LEqual (Arg0, DSMU)) { // USB capabilities UUID + Switch (ToInteger (Arg2)) { + Case (0) { // Function 0: List of supported functions + Return (Buffer () { 0x41 }) // 0x41 - Functions 0 and 6 supported + } + Case (6) { // Function 6: RegisterAccessType + Return (Buffer () { 0x01 }) // 0x01 - Must use 32bit register access + } + Default { } // Unsupported + } + } + return (Buffer () { 0x00 }) // Return 0x00 for anything unsupported + } } // end XHC0 } //end SCB0 } //end scope sb -- 2.30.2.windows.1 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#80106): https://edk2.groups.io/g/devel/message/80106 Mute This Topic: https://groups.io/mt/85307462/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-