[PATCH] arm64: dts: qcom: agatti: Make the ADSP remote heap no-map

[PATCH] arm64: dts: qcom: agatti: Make the ADSP remote heap no-map

[Benjamin Kelenyi]

The ADSP remote heap is declared as a reusable CMA pool. The ADSP has no
IOMMU, so fastrpc hands the whole region to the DSP with
qcom_scm_assign_mem() when it probes, while CMA keeps lending the pool's
pages to movable allocations. Once memory runs low the kernel touches a
page the DSP now owns, and the board resets without an oops.

On an Arduino UNO Q (QRB2210, 4 GB), writing and reading back 3.5 GB
through the page cache resets the board within seconds. With fastrpc
blacklisted, or with the heap declared no-map, the same test passes
repeatedly.

Declare the heap no-map, so the kernel never uses it, as the other
platforms' remote heaps are.

Fixes: 3fbf3b85bf86 ("arm64: dts: qcom: agatti: Add memory-region for audio PD")
Link: https://lore.kernel.org/all/20260908070331.2189A1F00A3A@smtp.kernel.org/
Signed-off-by: Benjamin Kelenyi <benjamin@wendy.sh>
---
 arch/arm64/boot/dts/qcom/agatti.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/qcom/agatti.dtsi b/arch/arm64/boot/dts/qcom/agatti.dtsi
index d9f4cbf..3ff97ea 100644
--- a/arch/arm64/boot/dts/qcom/agatti.dtsi
+++ b/arch/arm64/boot/dts/qcom/agatti.dtsi
@@ -385,7 +385,7 @@
 		adsp_rpc_remote_heap_mem: adsp-rpc-remote-heap {
 			compatible = "shared-dma-pool";
 			alloc-ranges = <0x0 0x0 0x1 0x0>;
-			reusable;
+			no-map;
 			alignment = <0x0 0x400000>;
 			size = <0x0 0x800000>;
 		};
-- 
2.43.0