于 2018年4月3日 GMT+08:00 下午7:41:41, Andre Przywara <[email protected]> 写到: >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?
It's also relevant with A80, theortically. And Allwinner is continously producing Cortex-A7 SoCs, which might use this design. > >> 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
