Add pcie-32bit-dma-overlay-pi5 to enable 32bit DMA on the Pi 5's external PCIe

Changes dma-ranges in the pcie1 component of the bcm2712 dts in order to ensure that the DMA addressing space is 32bits, at the expense of having to bounce buffers.

Signed-off-by: Rodrigo Rosmaninho <[email protected]>

Author: RodrigoRosmaninho

arch/arm/boot/dts/overlays/Makefile

@@ -183,6 +183,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	pca953x.dtbo \
 	pcf857x.dtbo \
 	pcie-32bit-dma.dtbo \
+	pcie-32bit-dma-pi5.dtbo \
 	pibell.dtbo \
 	pifacedigital.dtbo \
 	pifi-40.dtbo \

arch/arm/boot/dts/overlays/README

@@ -3394,6 +3394,12 @@ Load:   dtoverlay=pcie-32bit-dma
 Params: <None>
 
 
+Name:   pcie-32bit-dma-pi5
+Info:   Force PCIe config to support 32bit DMA addresses at the expense of
+        having to bounce buffers (on the Pi 5).
+Load:   dtoverlay=pcie-32bit-dma-pi5
+Params: <None>
+
 [ The pcf2127-rtc overlay has been deleted. See i2c-rtc. ]
 
 

arch/arm/boot/dts/overlays/overlay_map.dts

@@ -185,6 +185,11 @@
 
 	pcie-32bit-dma {
 		bcm2711;
+		bcm2712 = "pcie-32bit-dma-pi5";
+	};
+
+	pcie-32bit-dma-pi5 {
+		bcm2712;
 	};
 
 	pi3-act-led {

arch/arm/boot/dts/overlays/pcie-32bit-dma-pi5-overlay.dts

@@ -0,0 +1,26 @@
+/*
+ * pcie-32bit-dma-pi5-overlay.dts
+ */
+
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2712";
+
+	fragment@0 {
+		target = <&pcie1>;
+		__overlay__ {
+			/*
+			 * The size of the range is rounded up to a power of 2,
+			 * so the range ends up being 0-4GB, and the MSI vector
+			 * gets pushed beyond 4GB.
+			 */
+			#address-cells = <3>;
+			#size-cells = <2>;
+			dma-ranges = <0x02000000 0x0 0x00000000 0x0 0x00000000
+				      0x0 0x80000000>;
+		};
+	};
+
+};