Hi, On 03/04/18 12:34, Maxime Ripard wrote: > On Tue, Apr 03, 2018 at 11:13:17AM +0100, Andre Przywara wrote: >>>>>> For hacking it, see my implementation in v1, which assumes the >>>>>> only size supported bigger than 2GiB is 3GiB (which is >>>>>> acceptable on sunxi, but might not work on other platforms). >>>>>> >>>>>> As Andre said, that function has another big problem -- it detects >>>>>> memory with writing to it. This is risky. >>>>> >>>>> How is it risky when it's done by the SPL? >>>> >>>> Originally that was my confusion as well: It's not the SPL calling that >>>> function. The DRAM controller init function in there knows very >>>> precisely how much DRAM we have, but we don't communicate this to U-Boot >>>> proper. So U-Boot *proper* goes ahead and probes the DRAM. This means it >>>> could step into secure memory, for instance. On sunxi64 we have the ATF >>>> running between SPL and U-Boot, also all kind of secure payloads could >>>> already have been registered. >>>> So I wonder if it would be easier to somehow pass on this *one* word of >>>> information between SPL and U-Boot proper to avoid calling this function >>>> altogether? >>> >>> That would definitely make sense yes. >> >> So since the SPL loads the DT anyway (from the FIT image) and puts it at >> the end of the U-Boot (proper) binary, wouldn't it be the easiest to >> just patch the actual DRAM size in there? >> IIRC we don't have any FDT write code in the SPL at the moment, and >> pulling it in would probably push it over the edge again, but: > > That assumes that you are loading a FIT image, which might or might > not be the case, and on most arm32 chips, most likely won't.
That's true, but my understanding is that this >4GB is only relevant for 64-bit SoCs, where we mandate FIT images, don't we? > I guess we'd need to find another way (put some information in an > SRAM somewhere?) to try to do that for all variants. Oh, so your aim at getting rid of the call to the memory probing function at all? I was just assuming that we change it for the purpose of this 3GB support, which would be 64-bit only? Cheers, Andre _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
