Partition alignment

[MarkusHess]

Hi,

in the flash_l4t_t194_spi_emmc_p3668_rootfs_ab.xml, the secure-os_b and RECNAME partitions have the start_location parameter set which is aligned to 0x100000:

        <partition name="secure-os_b" type="tos" oem_sign="true">
            <allocation_policy> sequential </allocation_policy>
            <filesystem_type> basic </filesystem_type>
            <start_location> 0x386100000 </start_location> <!-- aligned to 0x100000 -->
            <size> 2621440 </size>
            <file_system_attribute> 0 </file_system_attribute>
            <allocation_attribute> 8 </allocation_attribute>
            <percent_reserved> 0 </percent_reserved>
            <filename> TOSFILE </filename>
            <description> **Required.** Chain B; contains the trusted OS. </description>
        </partition>
...
        <partition name="RECNAME" type="kernel">
            <allocation_policy> sequential </allocation_policy>
            <filesystem_type> basic </filesystem_type>
            <start_location> 0x38CA00000 </start_location> <!-- aligned to 0x100000 -->
            <size> RECSIZE </size>
            <file_system_attribute> 0 </file_system_attribute>
            <allocation_attribute> 8 </allocation_attribute>
            <percent_reserved> 0 </percent_reserved>
            <description> **Required.** Contains recovery image. </description>
            <filename> RECFILE </filename>
        </partition>

I have a huge gap in front of the secure-os_b and would like to reduce this gap to gain more space for the UDA partition. Is it safe to remove the start_location elements so that they start right after the previous partitions? Or is a gap and/or the alignement necessary?

[KevinFFF]

Hi MarkusHess,

Are you using the devkit or custom board for Xavier NX?
What’s your Jetpack version in use?

We don’t suggest to modify the offset for the partition since it may affect image-based OTA feature that the new partition layout does not match the previous one.

Have you considered to use external NVMe SSD for more available space?

[MarkusHess]

Hi KevinFFF,

we use a custom carrier board and L4T 35.5. Could you describe what could happen if we modify the offset? It is not clear for me in which cases OTA would break.

[KevinFFF]

If you know what you are doing, then it should be find to customize the offset.
You have to customize the exact same partition layout in every release for OTA update since it does not support for partition layout change during OTA.