gpoulios commented on code in PR #16729:
URL: https://github.com/apache/nuttx/pull/16729#discussion_r2208318032


##########
drivers/misc/optee.c:
##########
@@ -345,6 +346,10 @@ optee_shm_to_page_list(FAR struct optee_shm *shm, FAR 
uintptr_t *list_pa)
       *list_pa = optee_va_to_pa(list) | pgoff;
     }
 
+#ifndef CONFIG_ARCH_USE_MMU

Review Comment:
   If you’re asking why the MMU has this behaviour, I believe it is because the 
DRAM regions are typically configured as `MT_NORMAL` 
([eg1](https://github.com/apache/nuttx/blob/master/arch/arm64/src/qemu/qemu_boot.c#L65),
 
[eg2](https://github.com/apache/nuttx/blob/master/arch/arm64/src/common/arm64_mmu.c#L201),
 
[eg3](https://github.com/apache/nuttx/blob/master/arch/arm64/src/imx9/imx9_boot.c#L65))
 which translates in page tables [marked as 
inner-shareable](https://github.com/apache/nuttx/blob/def76c90d5648f64b2ef51175fb3327e2d8d9352/arch/arm64/src/imx9/imx9_boot.c#L65).
 According to A-profile ref. manual, B2.10.1.1.1:
   
   > Each Inner Shareability domain contains a set of observers that are data 
coherent for each member of that set for data accesses with the Inner Shareable 
attribute made by any member of that set.



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