apollo4x: build failure on kernel/cache/ Twister tests

[pillo79]

Describe the bug

The kernel/cache test suite fails on the apollo4p_evb and apollo4p_blue_kxr_evb boards due to missing symbols. It appears that (the HAL?) does not declare the SCB_* cache control functions that are used by arch/arm/core/cortex_m/cache.c when CONFIG_CACHE_MANAGEMENT is defined.

To Reproduce

Run west twister -c -T tests/kernel/cache/ -p apollo4p_evb.
On current Zephyr main (f5ce047, zephyrproject-rtos/hal_ambiq@f6858cb), tests fail to build with this error:

FAILED: zephyr/arch/arch/arm/core/cortex_m/CMakeFiles/arch__arm__core__cortex_m.dir/cache.c.obj 
ccache zephyr-sdk-0.16.4/arm-zephyr-eabi/bin/arm-zephyr-eabi-gcc -DKERNEL -DK_HEAP_MEM_POOL_SIZE=0 -DTC_RUNID=c0f20f410652dfe4df7d454c06f392ed -D__PROGRAM_START -D__ZEPHYR_SUPERVISOR__ -D__ZEPHYR__=1 -Izephyr/kernel/include -Izephyr/arch/arm/include -Izephyr/include -Izephyr/twister-out/apollo4p_evb/tests/kernel/cache/kernel.cache.api.minimallibc/zephyr/include/generated -Izephyr/soc/ambiq -Izephyr/soc/ambiq/apollo4x/. -Izephyr/soc/ambiq/. -Izephyr/subsys/testsuite/include -Izephyr/subsys/testsuite/ztest/include -Icore/include -Imodules/hal/cmsis/CMSIS/Core/Include -Izephyr/modules/cmsis/. -Imodules/hal/ambiq/CMSIS/AmbiqMicro/Include -Imodules/hal/ambiq/utils -Imodules/hal/ambiq/mcu/apollo4p -Imodules/hal/ambiq/mcu/apollo4p/hal -Imodules/hal/ambiq/components/bluetooth -isystem zephyr/lib/libc/minimal/include -isystem zephyr/lib/libc/common/include -isystem zephyr-sdk-0.16.4/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/include -isystem zephyr-sdk-0.16.4/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/include-fixed -Wshadow -fno-strict-aliasing -Werror -Os -imacros zephyr/twister-out/apollo4p_evb/tests/kernel/cache/kernel.cache.api.minimallibc/zephyr/include/generated/autoconf.h -ffreestanding -fno-common -g -gdwarf-4 -fdiagnostics-color=always -mcpu=cortex-m4 -mthumb -mabi=aapcs -mfp16-format=ieee --sysroot=zephyr-sdk-0.16.4/arm-zephyr-eabi/arm-zephyr-eabi -imacros zephyr/include/zephyr/toolchain/zephyr_stdint.h -Wall -Wformat -Wformat-security -Wno-format-zero-length -Wdouble-promotion -Wno-pointer-sign -Wpointer-arith -Wexpansion-to-defined -Wno-unused-but-set-variable -Werror=implicit-int -fno-pic -fno-pie -fno-asynchronous-unwind-tables -fno-reorder-functions --param=min-pagesize=0 -fno-defer-pop -fmacro-prefix-map=zephyr/tests/kernel/cache=CMAKE_SOURCE_DIR -fmacro-prefix-map=zephyr=ZEPHYR_BASE -fmacro-prefix-map=ZephyrCore=WEST_TOPDIR -ffunction-sections -fdata-sections -std=c99 -nostdinc -MD -MT zephyr/arch/arch/arm/core/cortex_m/CMakeFiles/arch__arm__core__cortex_m.dir/cache.c.obj -MF zephyr/arch/arch/arm/core/cortex_m/CMakeFiles/arch__arm__core__cortex_m.dir/cache.c.obj.d -o zephyr/arch/arch/arm/core/cortex_m/CMakeFiles/arch__arm__core__cortex_m.dir/cache.c.obj -c zephyr/arch/arm/core/cortex_m/cache.c
zephyr/arch/arm/core/cortex_m/cache.c: In function 'arch_dcache_enable':
zephyr/arch/arm/core/cortex_m/cache.c:20:9: error: implicit declaration of function 'SCB_EnableDCache' [-Werror=implicit-function-declaration]
   20 |         SCB_EnableDCache();
      |         ^~~~~~~~~~~~~~~~

(and all other SCB_* functions).

Impact

CI failures (sample log) on recent LLEXT PRs (such as #72358).

[RichardSWheatley]

I will take a look but we do not define CONFIG_CACHE_MANAGEMENT in our SOC and as such, this test is not compatible with our SOC at the moment.

This is planned for a future release but is not needed to run Zephyr.

[pillo79]

I see. Since we need that Kconfig in llext tests to ensure cache coherency, we will add an exclude to skip the Apollo targets for the time being. Thanks for looking into it!

[RichardSWheatley]

I see. Since we need that Kconfig in llext tests to ensure cache coherency, we will add an exclude to skip the Apollo targets for the time being. Thanks for looking into it!

It's being fixed today/tomorrow but it may take a week to get approved locally and then will be in PR for Zephyr. I will not tie any other code changes to it so that it should be approved quickly.

When we publish our SDK we do put the header files with the SCB_ functions in the SDK but they were removed (not sure why) when pushing the HAL to Zephyr.

So it is not a huge thing to update the HAL and add to the Kconfig for SOC.