linux-kernel - [PATCH v2 1/2] ARM: dts: bcm2711: force CMA into first GB of memory

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Message-Id: <20191106095945.22933-2-nsaenzjulienne@suse.de>
Date:   Wed,  6 Nov 2019 10:59:44 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     catalin.marinas@....com, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Eric Anholt <eric@...olt.net>, Stefan Wahren <wahrenst@....net>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        devicetree@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v2 1/2] 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 <nsaenzjulienne@...e.de>

---

Changes since v1:
  - Move into bcm2711.dtsi

 arch/arm/boot/dts/bcm2711.dtsi | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/arm/boot/dts/bcm2711.dtsi b/arch/arm/boot/dts/bcm2711.dtsi
index 1f3acd3363ea..6000a01652fa 100644
--- a/arch/arm/boot/dts/bcm2711.dtsi
+++ b/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 Raspberry Pi 4 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:
-- 
2.23.0