950-0640-ARM-dts-bcm2711-Restrict-CMA-to-first-768MB.patch

From 7b307016ed13cbb65e08b6a704912e5c9e5b81ac Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Tue, 14 Apr 2020 15:25:02 +0100
Subject: [PATCH] ARM: dts: bcm2711: Restrict CMA to first 768MB

The downstream 32-bit 2711 kernel configuration enables HIGHMEM for
access to more physical RAM. The HIGHMEM zone starts at 0x30000000
(768MB), and allowing the CMA zone to overlap that area causes a
failure during CMA activation.

Avoid the overlap by limiting CMA to the first 768MB. This is overly
restrictive on a 64-bit kernel, but shouldn't cause any practical
problems.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 arch/arm/boot/dts/bcm2711-rpi.dtsi | 5 +++++
 1 file changed, 5 insertions(+)

--- a/arch/arm/boot/dts/bcm2711-rpi.dtsi
+++ b/arch/arm/boot/dts/bcm2711-rpi.dtsi
@@ -45,6 +45,11 @@
 	};
 };
 
+&cma {
+	/* Limit cma to the lower 768MB to allow room for HIGHMEM on 32-bit */
+	alloc-ranges = <0x0 0x00000000 0x30000000>;
+};
+
 &soc {
 	thermal: thermal@7d5d2200 {
 		compatible = "brcm,avs-tmon-bcm2711";