[PATCH 1/3] arm64: dts: mediatek: mt8188-geralt: Reserve SCP dual-core memory region

[Michał Kopeć]

The trusted firmware on MT8188 protects 0x70000000-0x79ffffff (the SCP
core1 DRAM region) in the EMI MPU. Only the application processor and
the SCP may access it; accesses from other bus masters, including the
GPU, are silently dropped on write and return zeros on read.

The region is not reserved in the device tree, so Linux hands it out as
ordinary memory. Under memory pressure, GPU buffers and GPU page tables
end up there, which causes silent loss of GPU writes, translation
faults on page-table entries that are valid from the CPU's point of
view, and the GPU resets that follow.

Reserve the region, as the ChromeOS device tree does. No driver uses
it, so describe it as a plain no-map reservation.

Fixes: 5e6af7f54189 ("arm64: dts: mediatek: Introduce MT8188 Geralt platform based Ciri")
Signed-off-by: Michał Kopeć <michal@nozomi.space>
---
 arch/arm64/boot/dts/mediatek/mt8188-geralt.dtsi | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/boot/dts/mediatek/mt8188-geralt.dtsi b/arch/arm64/boot/dts/mediatek/mt8188-geralt.dtsi
index 801eee735afe6..d8edbde6ee4ac 100644
--- a/arch/arm64/boot/dts/mediatek/mt8188-geralt.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt8188-geralt.dtsi
@@ -197,6 +197,11 @@ adsp_dma_mem: memory@61000000 {
 			reg = <0 0x61000000 0 0x100000>;
 			no-map;
 		};
+
+		scp_dual_mem: memory@70000000 {
+			reg = <0 0x70000000 0 0xa000000>;
+			no-map;
+		};
 	};
 };
 
-- 
2.55.0