Drivers that allocate from the unencrypted PSRAM carve-out via
MALLOC_CAP_SPIRAM_NO_ENC currently have no way to verify after the fact
which pool a buffer came from. This is particularly relevant for callers
using heap_caps_malloc_prefer(MALLOC_CAP_SPIRAM_NO_ENC, MALLOC_CAP_SPIRAM),
where a silent fallback to encrypted PSRAM would still pass the typical
esp_ptr_external_ram() check.
Expose esp_psram_ptr_is_no_enc() in the public esp_psram.h header. It
performs a range check against the carve-out's virtual-address window and
returns false when PSRAM is not initialized or CONFIG_SPIRAM_ENC_EXEMPT is
disabled, so callers do not need to guard the call site with #if.
Also reference the helper from the External RAM documentation alongside
the heap_caps_malloc(MALLOC_CAP_SPIRAM_NO_ENC) usage example.
If the virtual-address pool is exhausted when reserving the unencrypted
PSRAM carve-out (the warning at L388 may already have fired for the main
mapping), esp_mmu_map_reserve_block_with_caps() returns an error rather
than aborting. Convert the previous assert() into a logged fallback that
disables the carve-out for this boot, mirroring the SPIRAM_ENC_EXEMPT_SIZE
>= psram_available_size path.
Also extend esp_psram_extram_test() to run the standard memory test on
the carve-out region when CONFIG_SPIRAM_ENC_EXEMPT is enabled, so the
unencrypted mapping is exercised on startup like the other PSRAM regions.
Adds CONFIG_SPIRAM_ENC_EXEMPT, available on chips that support per-page
PSRAM encryption configuration (esp32c5, esp32c61, esp32p4). When
enabled, esp_psram carves CONFIG_SPIRAM_ENC_EXEMPT_SIZE off the top of
PSRAM and maps it via the new mmu_hal_map_region_no_enc() helper, which
writes MMU entries without the SENSITIVE bit. The region is registered
as a separate heap pool reachable only through the new
MALLOC_CAP_SPIRAM_NO_ENC capability bit, so default SPIRAM allocations
cannot accidentally land there.
PSRAM encryption imposes alignment constraints that some DMA engines
(e.g. 2D-DMA) cannot satisfy. This option lets such workloads place
their buffers in unencrypted PSRAM while keeping the rest of PSRAM
(and flash) encrypted. Default disabled; security implications are
documented in the Kconfig help text.
