Emmc partition size align size for secure os

[weileng]

Hi,

For Jetson Xavier NX platform, JP5.02 GA version emmc partition table definition secure-os as follows.
flash_l4t_t194_spi_emmc_p3668.xml

<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>


<start_location> 0x386100000 </start_location> <!-- aligned to 0x100000 -->

if we want to adjust start_location, which just need to align to 0x10000, right?
or it must be 0x386100000. This definition location will cause emmc partition size to leave about 2G of space. For emmc only customer scenario, the total size is about 14G, such definition waste too much room size. Could you let us know why so setting? Thanks.

[JerryChang]

hello weileng,

it’s partition for trusty image, tos-trusty_t194.img. please see-also Trusty session for more details.
it’ll also need spare size, if not large enough for Trusty and its trusted applications you’ll see flash failure.
thanks

[weileng]

Hi Jerry,

Yes, it’s tos-trusty_t194.img. the total size is about 32M.
My two questions:
#1 Why “<start_location> 0x386100000 </start_location>”, it’s above 2G size room size offset, what’s the minimum room size should be keep.
#2 If we haven’t enable security boot, such “<start_location> 0x386100000 </start_location>” can be comments out or removed from flash_l4t_t194_spi_emmc_p3668.xml, right?

[JerryChang]

hello weileng,

it separates the partitions on slot-A and slot-B into different areas. so, the partition changes for one slot is handled in its own area, in order to keep it not affect the other slot.
and, yes, you may modify the partition layout with your own design.