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arch: common: Make nocache region loadable

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The `nocache` is not loadable, thus data stored therein cannot be
initialized by the startup code. This might be needed in special
cases. E.g. One might have a buffer which one wants to DMA into,
and which is a member of a struct. Other members of the struct one
may want to have initialized by the startup code.
The buffer thus should be placed in the `nocache` region, but for
the other members of the buffer to be initialized by the startup
code, the `nocache` region needs to be loadable.

Fix it by making the `nocache` region loadable. Adding a KConfig
symbol to do this optionally was considered, but deemed unnecessary
during the PR.

Signed-off-by: Julian Achatzi <mail@achatzi.pro>
This commit is contained in:
Julian Achatzi 2025-03-28 14:55:31 +01:00 • committed by Benjamin Cabé
commit f9168ae464
3 changed files with 10 additions and 2 deletions
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5
arch/common/nocache.ld
View file

@ -8,7 +8,7 @@
/* Copied from linker.ld */
/* Non-cached region of RAM */
SECTION_DATA_PROLOGUE(_NOCACHE_SECTION_NAME,(NOLOAD),)
SECTION_DATA_PROLOGUE(_NOCACHE_SECTION_NAME,,)
{
#if defined(CONFIG_MMU)
MMU_ALIGN;
@ -27,5 +27,6 @@ SECTION_DATA_PROLOGUE(_NOCACHE_SECTION_NAME,(NOLOAD),)
MPU_ALIGN(_nocache_ram_size);
#endif
_nocache_ram_end = .;
} GROUP_DATA_LINK_IN(RAMABLE_REGION, RAMABLE_REGION)
} GROUP_DATA_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)
_nocache_ram_size = _nocache_ram_end - _nocache_ram_start;
_nocache_load_start = LOADADDR(_NOCACHE_SECTION_NAME);

1
include/zephyr/linker/linker-defs.h
View file

@ -225,6 +225,7 @@ extern char __sg_size[];
extern char _nocache_ram_start[];
extern char _nocache_ram_end[];
extern char _nocache_ram_size[];
extern char _nocache_load_start[];
#endif /* CONFIG_NOCACHE_MEMORY */
/* Memory owned by the kernel. Start and end will be aligned for memory

6
kernel/xip.c
View file

@ -31,6 +31,12 @@ void z_data_copy(void)
z_early_memcpy(&__ramfunc_region_start, &__ramfunc_load_start,
__ramfunc_end - __ramfunc_region_start);
#endif /* CONFIG_ARCH_HAS_RAMFUNC_SUPPORT */
#ifdef CONFIG_ARCH_HAS_NOCACHE_MEMORY_SUPPORT
#if CONFIG_NOCACHE_MEMORY
z_early_memcpy(&_nocache_ram_start, &_nocache_load_start,
(uintptr_t) &_nocache_ram_size);
#endif /* CONFIG_NOCACHE_MEMORY */
#endif /* CONFIG_ARCH_HAS_NOCACHE_MEMORY_SUPPORT */
#if DT_NODE_HAS_STATUS_OKAY(DT_CHOSEN(zephyr_ccm))
z_early_memcpy(&__ccm_data_start, &__ccm_data_load_start,
__ccm_data_end - __ccm_data_start);