> On 15 Mar, 2016, at 05:47, [email protected] wrote:
> 
> SoCs often have multiple functional units on the same die. For radios that 
> allows for a pipeline. You can limit what an EPROM will accept with a crypto 
> signature.
> 
> This is common stuff.

As an example of this, AMD’s APUs and GPUs require several different firmware 
blobs to bring up their 3D capabilities.  The on-board BIOS supplies only what 
is necessary for basic SVGA framebuffer mode, which the operating system can 
use as a stopgap until the drivers are installed.

In Linux, these firmware blobs are identified by the IP block’s codename.  Most 
APUs and GPUs require a SUMO or SUMO2 blob to bring up the RAMDACs, and a 
separate GPU-specific blob (VERDE for my 7770) for the graphics engine itself, 
which takes up a much larger portion of the die.

I’m not sure whether these blobs are signed in AMD’s system, but they could be. 
 Their APUs have a Cortex-A5 based “secure processor” which could in principle 
be tied into the firmware-loading process, and probably has its own secure ROM. 
 A Cortex-M microcontroller core and ROM to do the job on a GPU would be tiny.

 - Jonathan Morton

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