The Thingy:91 X board files allocate only 32 kB to the TF-M secure
partition (slot0_s_partition). This is too small to support
CONFIG_TFM_PROFILE_TYPE_MEDIUM, which is required for ECDSA / PSA
Crypto persistent key storage. The nRF9151 DK board files allocate
256 kB to the same partition and work correctly.
Could Nordic provide an alternate partition layout for the Thingy:91 X
-- similar to the nrf91_crypto_partitions.dtsi pattern used for other
nRF91 Series targets -- that allocates sufficient secure flash for the
Medium profile?
Details
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The problem shows up at runtime as -134 (ENOTSUP) from
psa_generate_key(). The root cause is that the Thingy:91 X board
default enables CONFIG_TFM_PROFILE_TYPE_MINIMAL, which does not support
ECDSA. Switching to the Medium profile requires more secure flash than
the current partition provides.
Comparing the two board partition layouts makes the problem clear:
DK Thingy:91X
slot0_s_partition 256 kB 32 kB
slot0_ns_partition 192 kB 800 kB
MCUboot overhead 64 kB 192 kB
TF-M Medium profile ~160 kB overflows
The DK build with CONFIG_TFM_PROFILE_TYPE_MEDIUM in sysbuild/tfm.conf
produces a working ECDSA build. The identical configuration overflows
immediately on the Thingy:91 X.
We are not asking for help debugging our specific build. We are asking
Nordic to provide an official, tested partition layout for the
Thingy:91 X that supports the Medium TF-M profile -- the same way
nrf91_crypto_partitions.dtsi serves that purpose for other nRF91
Series boards.