linux-kernel - [PATCH] ARM: dts: bcm283x: Unify CMA configuration

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Date:   Fri, 10 Jan 2020 18:29:35 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Stefan Wahren <wahrenst@....net>
Cc:     phil@...pberrypi.org, devicetree@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ARM: dts: bcm283x: Unify CMA configuration

With the introduction of the Raspberry Pi 4 we were forced to explicitly
configure CMA's location, since arm64 defaults it into the ZONE_DMA32
memory area, which is not good enough to perform DMA operations on that
device. To bypass this limitation a dedicated CMA DT node was created,
explicitly indicating the acceptable memory range and size.

That said, compatibility between boards is a must on the Raspberry Pi
ecosystem so this creates a common CMA DT node so as for DT overlays to
be able to update CMA's properties regardless of the board being used.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
---

If this doesn't make it into v5.5 I'd be tempted to add:
Fixes: d98a8dbdaec6 ("ARM: dts: bcm2711: force CMA into first GB of memory")

 arch/arm/boot/dts/bcm2711.dtsi | 33 +++++++++++++--------------------
 arch/arm/boot/dts/bcm283x.dtsi | 13 +++++++++++++
 2 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi
index 8687534d4528..c8e4041308e0 100644
--- a/arch/arm/boot/dts/bcm2711.dtsi
+++ b/arch/arm/boot/dts/bcm2711.dtsi
@@ -12,26 +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;
-		};
-	};
-
-
 	soc {
 		/*
 		 * Defined ranges:
@@ -869,6 +849,19 @@ pin-rts {
 	};
 };
 
+&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>;
diff --git a/arch/arm/boot/dts/bcm283x.dtsi b/arch/arm/boot/dts/bcm283x.dtsi
index 839491628e87..6128baed83c2 100644
--- a/arch/arm/boot/dts/bcm283x.dtsi
+++ b/arch/arm/boot/dts/bcm283x.dtsi
@@ -30,6 +30,19 @@ chosen {
 		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>;
-- 
2.24.1