Configure CMA using DT

arch/arm/boot/dts/bcm2711-rpi-4-b.dts

@@ -195,7 +195,7 @@
 
 / {
 	chosen {
-		bootargs = "coherent_pool=1M 8250.nr_uarts=1 cma=64M";
+		bootargs = "coherent_pool=1M 8250.nr_uarts=1";
 	};
 
 	aliases {
@@ -215,10 +215,6 @@
 	};
 
 	/delete-node/ wifi-pwrseq;
-
-	reserved-memory {
-		/delete-node/ linux,cma;
-	};
 };
 
 &mmcnr {

arch/arm/boot/dts/bcm2711.dtsi

@@ -12,25 +12,6 @@
 
 	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;
-		};
-	};
-
 	vc4: gpu {
 		compatible = "brcm,bcm2711-vc5";
 		status = "disabled";
@@ -992,6 +973,19 @@
 	};
 };
 
+&rmem {
+	#address-cells = <2>;
+};
+
+&cma {
+	/*
+	 * 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).
+	 */
+	alloc-ranges = <0x0 0x00000000 0x40000000>;
+};
+
 &i2c0 {
 	compatible = "brcm,bcm2711-i2c", "brcm,bcm2835-i2c";
 	interrupts = <GIC_SPI 117 IRQ_TYPE_LEVEL_HIGH>;

arch/arm/boot/dts/bcm283x.dtsi

@@ -30,6 +30,19 @@
 		stdout-path = "serial0:115200n8";
 	};
 
+	rmem: reserved-memory {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+
+		cma: linux,cma {
+			compatible = "shared-dma-pool";
+			size = <0x4000000>; /* 64MB */
+			reusable;
+			linux,cma-default;
+		};
+	};
+
 	thermal-zones {
 		cpu_thermal: cpu-thermal {
 			polling-delay-passive = <0>;

arch/arm/boot/dts/overlays/Makefile

@@ -28,6 +28,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	audiosense-pi.dtbo \
 	audremap.dtbo \
 	balena-fin.dtbo \
+	cma.dtbo \
 	dht11.dtbo \
 	dionaudio-loco.dtbo \
 	dionaudio-loco-v2.dtbo \

arch/arm/boot/dts/overlays/README

@@ -554,6 +554,19 @@ Info:   This overlay is now deprecated - see i2c-sensor
 Load:   <Deprecated>
 
 
+Name:   cma
+Info:   Set custom CMA sizes, only use if you know what you are doing, might
+        clash with other overlays like vc4-fkms-v3d and vc4-kms-v3d.
+Load:   dtoverlay=cma,<param>=<val>
+Params: cma-256                 CMA is 256MB (needs 1GB)
+        cma-192                 CMA is 192MB (needs 1GB)
+        cma-128                 CMA is 128MB
+        cma-96                  CMA is 96MB
+        cma-64                  CMA is 64MB
+        cma-size                CMA size in bytes, 4MB aligned
+        cma-default             Use upstream's default value
+
+
 Name:   dht11
 Info:   Overlay for the DHT11/DHT21/DHT22 humidity/temperature sensors
         Also sometimes found with the part number(s) AM230x.
@@ -2675,6 +2688,8 @@ Params: cma-256                 CMA is 256MB (needs 1GB)
         cma-128                 CMA is 128MB
         cma-96                  CMA is 96MB
         cma-64                  CMA is 64MB
+        cma-size                CMA size in bytes, 4MB aligned
+        cma-default             Use upstream's default value
 
 
 Name:   vc4-kms-kippah-7inch
@@ -2692,6 +2707,8 @@ Params: cma-256                 CMA is 256MB (needs 1GB)
         cma-128                 CMA is 128MB
         cma-96                  CMA is 96MB
         cma-64                  CMA is 64MB
+        cma-size                CMA size in bytes, 4MB aligned
+        cma-default             Use upstream's default value
         audio                   Enable or disable audio over HDMI (default "on")
 
 
@@ -2703,6 +2720,8 @@ Params: cma-256                 CMA is 256MB
         cma-128                 CMA is 128MB
         cma-96                  CMA is 96MB
         cma-64                  CMA is 64MB
+        cma-size                CMA size in bytes, 4MB aligned
+        cma-default             Use upstream's default value
         audio                   Enable or disable audio over HDMI0 (default
                                 "on")
         audio1                  Enable or disable audio over HDMI1 (default

arch/arm/boot/dts/overlays/cma-overlay.dts

@@ -0,0 +1,32 @@
+/*
+ * cma.dts
+ */
+
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2835";
+
+	fragment@0 {
+		target = <&cma>;
+		frag0: __overlay__ {
+			/*
+			 * The default size when using this overlay is 256 MB
+			 * and should be kept as is for backwards
+			 * compatibility.
+			 */
+			size = <0x10000000>;
+		};
+	};
+
+	__overrides__ {
+		cma-256 = <&frag0>,"size:0=",<0x10000000>;
+		cma-192 = <&frag0>,"size:0=",<0xC000000>;
+		cma-128 = <&frag0>,"size:0=",<0x8000000>;
+		cma-96  = <&frag0>,"size:0=",<0x6000000>;
+		cma-64  = <&frag0>,"size:0=",<0x4000000>;
+		cma-size = <&frag0>,"size:0"; /* in bytes, 4MB aligned */
+		cma-default = <0>,"-0";
+	};
+};

arch/arm/boot/dts/overlays/upstream-overlay.dts

@@ -1,4 +1,4 @@
-// redo: ovmerge -c vc4-kms-v3d-overlay.dts,cma-96 dwc2-overlay.dts,dr_mode=otg
+// redo: ovmerge -c vc4-kms-v3d-overlay.dts,cma-default dwc2-overlay.dts,dr_mode=otg
 
 /dts-v1/;
 /plugin/;
@@ -8,114 +8,90 @@
 / {
 	compatible = "brcm,bcm2835";
 	fragment@0 {
-		target-path = "/chosen";
+		target = <&cma>;
 		__dormant__ {
-			bootargs = "cma=256M";
+			size = <0x10000000>;
 		};
 	};
 	fragment@1 {
-		target-path = "/chosen";
-		__dormant__ {
-			bootargs = "cma=192M";
-		};
-	};
-	fragment@2 {
-		target-path = "/chosen";
-		__dormant__ {
-			bootargs = "cma=128M";
-		};
-	};
-	fragment@3 {
-		target-path = "/chosen";
-		__overlay__ {
-			bootargs = "cma=96M";
-		};
-	};
-	fragment@4 {
-		target-path = "/chosen";
-		__dormant__ {
-			bootargs = "cma=64M";
-		};
-	};
-	fragment@5 {
 		target = <&i2c2>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@6 {
+	fragment@2 {
 		target = <&fb>;
 		__overlay__ {
 			status = "disabled";
 		};
 	};
-	fragment@7 {
+	fragment@3 {
 		target = <&pixelvalve0>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@8 {
+	fragment@4 {
 		target = <&pixelvalve1>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@9 {
+	fragment@5 {
 		target = <&pixelvalve2>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@10 {
+	fragment@6 {
 		target = <&hvs>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@11 {
+	fragment@7 {
 		target = <&hdmi>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@12 {
+	fragment@8 {
 		target = <&v3d>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@13 {
+	fragment@9 {
 		target = <&vc4>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@14 {
+	fragment@10 {
 		target = <&clocks>;
 		__overlay__ {
 			claim-clocks = <BCM2835_PLLD_DSI0 BCM2835_PLLD_DSI1 BCM2835_PLLH_AUX BCM2835_PLLH_PIX>;
 		};
 	};
-	fragment@15 {
+	fragment@11 {
 		target = <&vec>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@16 {
+	fragment@12 {
 		target = <&txp>;
 		__overlay__ {
 			status = "okay";
 		};
 	};
-	fragment@17 {
+	fragment@13 {
 		target = <&hdmi>;
 		__dormant__ {
 			dmas;
 		};
 	};
-	fragment@18 {
+	fragment@14 {
 		target = <&usb>;
 		#address-cells = <1>;
 		#size-cells = <1>;