Hello,
The imx8mp.dtsi device tree include shipped in https://github.com/nxp-imx/linux-imx (all branches) defined a `isp0_reserved` memory region which is unmapped by linux even if isp0 itself is disabled.
Disabling the memory region immediately frees up 256MB of memory (just disabling the node is enough, see below patch)
The comment immediately above states "used only by tuning tool, can be removed for normal case" so there probably is no reason to keep it enabled by default, please report this to whomever if may concern (the linux upstream dtsi does not contain this section)
From c26321365174d71cf8642f309f16eeefda36c7c9 Mon Sep 17 00:00:00 2001
From: Dominique Martinet <dominique.martinet@atmark-techno.com>
Date: Fri, 28 Apr 2023 12:48:47 +0900
Subject: [PATCH] arm64: imx8mp.dtsi: disable isp0_reserved by default
isp0_reserved is 256MB big and described as "used only by tuning tool,
can be removed for normal case": so disable it by default,
and anyone enabling isp0 must enable the reserved memory as well
manually
(why wouldn't linux automatically do this...)
This increases the available memory on Armadillo IoT G4 as confirmed
below.
Before:
armadillo:~# free -m
total used free shared buff/cache available
Mem: 1668 884 209 67 575 629
After:
armadillo:~# free -m
total used free shared buff/cache available
Mem: 1924 341 1531 1 52 1524
Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
---
arch/arm64/boot/dts/freescale/imx8mp.dtsi | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
index dccf24c90862..dde207a7f348 100755
--- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
@@ -217,6 +217,7 @@ dsp_vdev0buffer: vdev0buffer@94300000 {
isp0_reserved: isp0@94400000 {
no-map;
reg = <0 0x94400000 0 0x10000000>;
+ status = "disabled";
};
};
--
2.39.2
Thanks.
