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From f3e5f85353153a6941fc9e32871b5037e875d1ae Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Wed, 17 May 2023 13:39:18 +0100
Subject: [PATCH] ARM: dts: bcm2711-rpi: Set a 1GB ZONE_DMA limit
The arm64 initialisation uses the physical address reachable by all
DMA controllers to set the size of ZONE_DMA. This fails on BCM2711
with the current dts files because the declaration of the I/O space
fools it into thinking the legacy 30-bit DMA channels can see most
of the 32-bit space.
Take advantage of the simple nature of the implementation by adding
a node with a restricted dma-ranges property solely so to act as the
limiting factor in the calculation.
See: https://github.com/raspberrypi/linux/issues/5470
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
arch/arm/boot/dts/bcm2711-rpi-ds.dtsi | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/arch/arm/boot/dts/bcm2711-rpi-ds.dtsi
+++ b/arch/arm/boot/dts/bcm2711-rpi-ds.dtsi
@@ -63,6 +63,16 @@
spi6 = &spi6;
/delete-property/ intc;
};
+
+ /*
+ * Add a node with a dma-ranges value that exists only to be found
+ * by of_dma_get_max_cpu_address, and hence limit the DMA zone.
+ */
+ zone_dma {
+ #address-cells = <1>;
+ #size-cells = <1>;
+ dma-ranges = <0x0 0x0 0x0 0x40000000>;
+ };
};
&vc4 {
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