Re: [edk2-platforms][PATCH 1/1] Platform/RaspberryPi/RPi4: Add _DSM ACPI method for 32-bit MMIO xHCI access


Ard Biesheuvel
 

On Wed, 1 Sept 2021 at 18:46, Pete Batard <pete@akeo.ie> wrote:

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.
Very nice!

Signed-off-by: Pete Batard <pete@akeo.ie>
Tested-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

Pushed as 6e68849e5545..901d3c52ed23

---
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

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