The PLM supports storing of images in the DDR memory during boot time so
that the images can be used later in cases like delay load, subsystem restart, and
suspend/resume. This helps in reducing the load times because loading images from the
DDR memory is faster than loading them from other boot devices. The
imagestore attribute in the bif of the boot PDI can be used
to specify the Image Store PDI sections.
PLM has access to a dedicated DDR memory location for storing user-requested PDIs. The allocated DDR location address and size is populated in the pre-defined RTCA region space for the PLM to get the Image Store configuration details.
You can also create or upgrade the image store during runtime by using partial PDIs. The address of the partial PDI loaded in the DDR memory along with the PDI ID can be passed to PLM using an IPI command (Add Image Store) and the PLM adds it into a PDI list. So, the PLM maintains a PDI list whose first entry is Boot PDI and rest of them are the PDI Addresses added during runtime. During any of these use cases where an image has to be restarted, the PLM goes through the PDI list from the latest entry and checks if the required image is present in the PDI and loads it. If an image is not found or if the loading fails, the PLM performs a fallback to the next entry of the list until it reaches the Boot PDI.