On 10/26/2016 01:12 PM, Stephen Warren wrote: > On 10/26/2016 01:54 PM, york sun wrote: >> On 10/26/2016 12:47 PM, Stephen Warren wrote: >>> >>> There are two data structures in ARM U-Boot that describe memory layout: >>> >>> 1) A list of RAM memory regions. U-Boot uses these to know where to >>> relocate itself to (it relocates itself to the top of RAM at boot), and >>> to fill in the /memory node when booting an OS using DT (and other >>> equivalent mechanisms when not using DT.) >>> >>> 2) For AArch64 specifically, there's a memory map table that defines all >>> RAM and MMIO regions, and the translation table attributes required for >>> those regions. >>> >>> Judging by your comments later in the original message, it sounds like >>> it'd be fine to read from these structures during any dcache clean >>> routine provided the table has already been cleaned. That makes using >>> the tables much more tractable:-) >>> >> >> I think we need to benchmark walking through the MMU tables. It can map >> huge amount of memory. For our case, it is more than 16GB. I have been >> reluctant to do so for the size. I am now back testing to revert _this_ >> patch, hoping to confirm what I learned from this discussion. After >> that, I will see how long it takes to flush all cached addresses by VA. > > Given the existence of the two data structures I mentioned above, I > don't think we'd ever need to walk the MMU translation tables (assuming > you mean the data structures U-Boot creates and configures into the > CPU's MMU), rather than just walking over the tiny number of entries in > those data structures? >
The list of RAM used by U-Boot is different from the total memory. U-Boot relocates itself to the gd->ram_top. We may have memory in second region, or even the third region. We also have other cached region other than RAM. I know for Layerscape SoCs, there is QMan portal has 64MB cached. If we consider to flush _all_ address, they should be included. I think the 2nd data structure you mentioned is the MMU table for aarch64, isn't it? York _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
