diff --git a/s/USB b/s/USB
index 01f048de88568b66fa050ea5da873d8da8420738..54b3057c920986f9343c97165407cdfcbe6902dd 100644
--- a/s/USB
+++ b/s/USB
@@ -63,7 +63,11 @@ HAL_USBControllerInfo
                 STR     a4, [a2, #HALUSBControllerInfo_DevNo]
                 LDR     a4, FB_CacheMode
                 STR     a4, [a2, #HALUSBControllerInfo_DMAOffset]
-                ADD     a4, ip, #MPHI_Base
+                CPUDetect a3
+                ; Raspberry Pi 4 / BCM2838 has no MPHI to do FIQ downgrade, but
+                ; does have a GIC which can fulfil the same requirement
+                LDRHI   a4, GICD_Base_Address
+                ADDLS   a4, ip, #MPHI_Base
                 STR     a4, [a2, #HALUSBControllerInfo_HW_MPHI]
                 MOV     a4, #iDev_GPU_HostPort
                 STR     a4, [a2, #HALUSBControllerInfo_DevNo_MPHI]