undefined | Better HN

0 pointstranspute2y ago0 comments

> The ARM SoC do not have an IME though...

RPi 4 boots from GPU/VPU running closed firmware (incl. Microsoft ThreadX RTOS), which retains full control over the OS application processor, https://www.fsf.org/resources/hw/single-board-computers

  Boards based on the Broadcom VideoCore 4 family, such as the Raspberry Pi, require non-free software to startup, although signature checks are not enforced. A free proof-of-concept replacement firmware has been developed, but it is not in a usable state, and development has halted.

  By default, the GPU requires a blob running in this same startup firmware. However, Broadcom also supplies an "experimental" free software stack, which could run without blobs, if the startup firmware were free.

0 comments

2 comments · 1 top-level

Joel_Mckay2y ago· 1 in thread

A boot-loader or GPU driver blob is different from an entire copy of Minix OS running on the Intel CPU that will boot-loop the hardware every 20 minutes if wiped.

The RISCV also offers something unique over Pi ARM chips, but little economic incentive to stop the shenanigans. ;)

transputeOP2y ago

Comment by the developer who attempted to create open firmware for RPi, https://github.com/christinaa/rpi-open-firmware/issues/37

> a lot of corners were cut to save time leading to what I believe is poor ARMv7+ Cortex IP integration (GIC, TrustZone, etc). So I stopped working on it. If those things were not the case (GIC working, "TZPCs" working, security working as intended, instead of NS forced to high on bridge, at least in my understanding) I would still work on it ...

ARM isn't a second class citizen on this platform, it's a third class citizen since BCM2709 (again this is an opinion) ... the features I wanted to tinker with the most are absent by design (cutting corners) and I'm not willing to resort to SW emulation of them through clever uses of the VPU.

Hopefully RPi 5 silicon offers a better foundation for open firmware.

j / k navigate · click thread line to collapse

Boards based on the Broadcom VideoCore 4 family, such as the Raspberry Pi, require non-free software to startup, although signature checks are not enforced. A free proof-of-concept replacement firmware has been developed, but it is not in a usable state, and development has halted. By default, the GPU requires a blob running in this same startup firmware. However, Broadcom also supplies an "experimental" free software stack, which could run without blobs, if the startup firmware were free.