ARM: dts: bcm2711: force CMA into first GB of memory

arm64 places the CMA in ZONE_DMA32, which is not good enough for the
Raspberry Pi 4 since it contains peripherals that can only address the
first GB of memory. Explicitly place the CMA into that area.

Signed-off-by: Nicolas Saenz Julienne <[email protected]>
Acked-by: Stefan Wahren <[email protected]>
Signed-off-by: Florian Fainelli <[email protected]>

Author: Nicolas Saenz Julienne

arch/arm/boot/dts/bcm2711.dtsi

@@ -12,6 +12,26 @@
 
 	interrupt-parent = <&gicv2>;
 
+	reserved-memory {
+		#address-cells = <2>;
+		#size-cells = <1>;
+		ranges;
+
+		/*
+		 * arm64 reserves the CMA by default somewhere in ZONE_DMA32,
+		 * that's not good enough for the BCM2711 as some devices can
+		 * only address the lower 1G of memory (ZONE_DMA).
+		 */
+		linux,cma {
+			compatible = "shared-dma-pool";
+			size = <0x2000000>; /* 32MB */
+			alloc-ranges = <0x0 0x00000000 0x40000000>;
+			reusable;
+			linux,cma-default;
+		};
+	};
+
+
 	soc {
 		/*
 		 * Defined ranges: