Example locating interrupt and main stacks in DTCM

[DerekSnell]

The attached example uses a linker script to place the pinned linker sections in DTCM. This includes the z_interrupt_stacks and z_main_stack. On the NXP i.MX RT SOCs, this can increase the performance substantially compared to leaving in the default external SDRAM.

The example is tested on the mimxrt1170_evk//cm7 board, and built with Zephyr v4.0.0.

pinned_hello_world.zip

[DerekSnell]

Marking as answered

[ofirshe]

Hey @DerekSnell,
I've tried applying this enhancement to the mimxrt1060_evk board but encountered a compilation error during the build process:

c:/users/ofirs/bsp/zephyr-sdk-0.16.8/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: zephyr/libzephyr.a(cbprintf_packaged.c.obj): in function `linker_is_in_rodata':
C:/Users/ofirs/bsp/zephyr/include/zephyr/linker/utils.h:54: undefined reference to `lnkr_pinned_rodata_start'
c:/users/ofirs/bsp/zephyr-sdk-0.16.8/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: C:/Users/ofirs/bsp/zephyr/include/zephyr/linker/utils.h:54: undefined reference to `lnkr_pinned_rodata_end'
collect2.exe: error: ld returned 1 exit status
ninja: build stopped: subcommand failed

The error seems to stem from missing linker symbols lnkr_pinned_rodata_start and lnkr_pinned_rodata_end.

For context, I'm using Zephyr version 4.0.99 (commit hash: 305ceba9204d9a7ee4bae0a6103ef4cbd9a1c54e).

Could you share how you resolved this issue on your end?

Thanks!

[DerekSnell]

Hi @ofirshe ,
Thanks for making me aware. My simple example did not have that issue. But I was able to replicate the build issue. I updated the example to include the pinned_rodata section, and I tested this on the mimxrt1060_evk board.

Best regards

[JaagupAverin]

We got this working on a more complicated application but also had to add pinned_data and pinned_text sections.

Additionally we moved ALL stacks to the DTCM with this patch:

From 094a29a8c938ab7c9a323c746991aeef4c8dcd1b Mon Sep 17 00:00:00 2001
From: JaagupA <[email protected]>
Date: Wed, 27 Aug 2025 14:44:14 +0300
Subject: [PATCH 2/2] Add CONFIG_LINKER_PINNED_STACKS.

Can be used to place all kernel stacks into the .pinned memory region, which can then in turn be moved by the application to whatever region desired, e.g DTCM.
---
 Kconfig.zephyr                       | 7 +++++++
 include/zephyr/linker/section_tags.h | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/Kconfig.zephyr b/Kconfig.zephyr
index c6cf8ded2ab..cf81078e6be 100644
--- a/Kconfig.zephyr
+++ b/Kconfig.zephyr
@@ -254,6 +254,13 @@ config LINKER_USE_PINNED_SECTION
 	  Requires that pinned sections exist in the architecture, SoC,
 	  board or custom linker script.
 
+
+config LINKER_PINNED_STACKS
+	bool "Place all stacks into pinned memory"
+	depends on LINKER_USE_PINNED_SECTION
+	help
+	  When selected, all kernel stacks will be placed into pinned memory.
+
 config LINKER_USE_ONDEMAND_SECTION
 	bool "Use Evictable Linker Section"
 	depends on DEMAND_MAPPING
diff --git a/include/zephyr/linker/section_tags.h b/include/zephyr/linker/section_tags.h
index ab73c044501..f86524ef228 100644
--- a/include/zephyr/linker/section_tags.h
+++ b/include/zephyr/linker/section_tags.h
@@ -70,7 +70,11 @@
 #else
 #define __incoherent
 #define __stackmem Z_GENERIC_SECTION(.user_stacks)
+#if defined(CONFIG_LINKER_PINNED_STACKS)
+#define __kstackmem __pinned_noinit
+#else
 #define __kstackmem __noinit
+#endif
 #endif /* CONFIG_KERNEL_COHERENCE */
 
 #if defined(CONFIG_LINKER_USE_BOOT_SECTION)

Does that seem valid?