Thanks to both of you. This is quite helpful.

On Tue, Aug 8, 2023 at 1:47 AM Indan Zupancic <[email protected]> wrote:

> [CAUTION: Non-UBC Email]
>
> Hello Sid,
>
> On 2023-08-08 05:20, Sid Agrawal wrote:
> > 1. Looking at the DTS files for tqma8xqp-1gb in the seL4 repo. I see
> > one big file and another overlay. Why are there two for the same
> > board? I would have understood if one was for the SoC and another
> > for the board.
> > - tools/dts/tqma8xqp1gb.dts
> >
> > - src/plat/tqma8xqp1gb/overlay-tqma8xqp1gb.dts
>
> See Ivan's answer. As I was involved with the tqma port, I can confirm
> that tools/dts/tqma8xqp1gb.dts is the de-compiled Linux DTB that came
> on the SD card with the STKa8Xx dev board, see:
>
> https://www.tq-group.com/en/products/tq-embedded/arm-architecture/stka8xx/
>
> Specifically, I think it's based on version 25 of the SDK:
>
> https://support.tq-group.com/en/arm/tqma8xx/linux/yocto/overview
>
> The reason there is no board DTS file is because tqma is a module
> which exposes almost all pins, so there are very few module hardware
> choices made. And seL4 only uses on-chip peripherals, so nothing
> board specific is left. In hindsight the tqma8xqp1gb platform would
> have been better named imx8qxp, with configurable UART and memory
> amount.
>
> > 2. I see that the VMM example
> > (https://github.com/Ivan-Velickovic/sel4cp_vmm), as well as the sDDF
> > example (https://github.com/lucypa/sDDF/tree/main/echo_server), uses
> > the iMX8MM-EVK board.
> > - How different are iMX8MM-EVK and tqma8xqp1gb?
>
> Very different for SoCs in the same product range, the iMX8MM-EVK
> is based on the i.MX8M Mini SoC. But most changes aren't really
> software visible.
>
> The imx8qxp SoC is very complex and annoying because of the SCU.
> If you don't need ECC memory, GPU, multiple displays and Ethernet
> ports, go for a different SoC without SCU. That said, if U-Boot
> configures the SCU correctly for your needs, you can ignore the
> whole SCU mess for a while.
>
> > - What is the preferred board for the sel4cp effort at Trustworthy
> > Systems? This way, I will just get that board, and it would be easier
> > for me to follow your efforts along the way and maybe even contribute
> > :)
>
> I don't know what board they use, but STKa8Xx, the tqma dev board,
> used to be very expensive.
>
> > 3. For the VMM example in particular.
> > - Is it correct to say that there are two dts files at play, one
> > needed by seL4(which we get from the seL4 repo) and the other needed
> > by the Linux Guest, which we get from the sel4cp_vmm repo?
>
> The seL4 one describes all hardware peripherals so that all
> the device untyped memory regions can be created. Assuming it
> correctly describes the SoC, it never needs to be changed or
> updated.
>
> The VMM one is needed to tell the Linux VM what hardware and
> memory it can actually use. Not all boards have all peripherals
> connected, so the sel4cp_vmm DTS file is also the board file
> describing the actual hardware available.
>
> Greetings,
>
> Indan
>
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