Hi Simon,
This is reading a lot of DT stuff very early, which may be slow. It is also reading from the DT in the bind() step which we sometimes have to do, but try to avoid.
Could we set up the livetree pre-bind? What about MMU? On armv8 at least this would have a huge impact on performance. I've done some measurements and there is at least 1 order of magnitude difference between parsing FDT with no caches vs parsing livetree with, it's huge.
That seems like a great idea to me, in general. The fact that SPL sets up the MMU on armv8 makes it more practical.
Well, on qcom we don't use SPL (yet?), we did have a cyclical dependency since we rely on DTB for the memory layout, although I have some patches to do all the memory parsing in board_fdt_blob_setup() since that's needed for multi-dtb FIT. So I guess we could enable caches at the same time.
Yes...it seems that enabling cache in SPL has become common on armv8.
As to the memory layout, I'm not sure what is happening there, but it seems that the DT does not describe it in general (at least not until U-Boot adds the nodes).
I suppose this depends on the platform. On Qualcomm we use DT as the source of truth as it lets us support many platforms (with totally different memory maps) with a single U-Boot binary, at least for development this is quite nice.
But for this series I believe we are going to have to define what happens in what phase. We have power_init_board() which is the old way of doing this...but perhaps we could use that as a way to start up regulators which are needed.
As to my question about whether this happens in SPL / pre-reloc / proper, I forgot that we have the bootph tags for that, so it should be fine. The main issue is that in U-Boot proper we will re-init the regulators even though that has already been done. Probably that can be handled by Kconfig or a flag in SPL handoff.
Ensuring that it isn't done multiple times sounds like the right approach to me.
OK...I wonder how we can solve this. Needs some though.
Also this seems to happen in SPL and again pre-reloc and again in U-Boot post-reloc?
Should we have a step in the init sequence where we set up the regulators, by calling regulators_enable_boot_on() ?
Regards, Simon