Re: [PATCH v11 3/6] arm64: dts: allwinner: Add Allwinner H616 .dtsi file

[Samuel Holland <samuel@sholland.org>]

Hi Andre, Jernej,

On 7/6/22 8:16 AM, Andre Przywara wrote:
> so after seemingly having finished writing this email, I realised that
> this won't really help, as I think this diverts the discussion. And the
> problem has been around for a while, and won't probably be solved easily
> or quickly. I think we agree to disagree here, or we should admit that
> there are different approaches ("bundled firmware" vs. "UEFI"), so in the
> interest of not blocking the H616 series:
> 
> Shall I just keep the firmware node? This would work both ways, whereas
> dropping the node would impede the "bundled firmware" approach?

Let me try to sum up the relevant portion of my thoughts (and save the rest for
elsewhere):

The only reason to add the reserved-memory node is to support externally-loaded
DTBs. By adding the node, we are committing to support externally-loaded DTBs on
this SoC.

Upgrading the kernel is not allowed to break boot. If we support
externally-loaded DTBs, that rule extends to DTBs shipped with the kernel.

If we remove the reserved-memory node, the combination of old U-Boot + new
externally-loaded DTB will stop booting (the kernel version is irrelevant).
Therefore, if we add the node, we can never remove it, full stop.

I will (begrudgingly) accept that, as long as the node matches what TF-A
actually generates today. That means, please:
 - Drop the label and update the node name
 - Reduce the size to 256 KiB, matching (BL31_LIMIT - BL31_BASE)

Regards,
Samuel