The PLM supports the Copy to Memory and Deferred Image Handoff features. Based on the scenario, you might have to defer loading a certain subsystem image in the PDI after a certain boot milestone, or defer the handing off to a certain subsystem image. This establishes a certain boot order and can be used to decrease boot time.
Copy to Memory
Images with the copy = <DDR
address> attribute specified against them in the BIF file are stored
at the specified address in DDR and then loaded during boot PDI load. Specifying the
copy attribute takes a backup of the image in
DDR, while loading the image. Specifying delay_load
in BIF for an image skips the loading of the image altogether.
Specifying copy = <DDR address>,
delay_load in BIF takes the back up of the image in DDR and skips
loading of the image altogether.
Images are loaded by an IPI command 0x10702 that takes the image ID, function
ID as an argument. The IPI command loads and executes these images
after all other images start their run. You cannot specify delay_load and delay_handoff
simultaneously for an image.
However, you can specify copy and
delay_handoff simultaneously for an image.
For partial PDIs, the Copy to Memory feature is not supported.
Deferred Image Handoff
You can pass the delay_handoff attribute to
the selected image IDs in the BIF file, which is an input to Bootgen. The PLM reads
the delay_handoff attribute and defers the handoff
of the images till the end of boot PDI load. In other words, the images with the
delay_handoff attribute specified, only start
running after the images without the delay_handoff
and copy = 1 attributes start their run. Deferred
Image Handoff is supported for both full PDIs and partial PDIs.