Hi Graeme, On Wed, Feb 8, 2012 at 7:38 PM, Graeme Russ <graeme.r...@gmail.com> wrote: > Hi Simon, > > On Wed, Feb 8, 2012 at 6:12 PM, Simon Glass <s...@chromium.org> wrote: > >> Also make sure that the I-Cache is on as early as possible. Relocation >> is done with the d-cache off so is slow. Takes about 40ms for me from > > Have a close look at the latest x86 patches (not yet pulled into mainline) > as an example of how this does not need to be the case. The sequence I > now use is: > > 1) Initialise 'Cache-As-RAM' (CAR) - Cache cannot be used to cache > SDRAM, otherwise the Stack and Global Data get trashed > 2) Create Stack and Global Data in CAR > 3) Initialise SDRAM > 4) Create a new stack in SDRAM > 5) 'Pivot' U-Boot - Move stack from CAR to SDRAM (U-Boot still running > in Flash) > 6) Copy Global Data into SDRAM (adjust the global data pointer to point > to the in-RAM copy) > 7) CAR is no longer used - Enable caching of SDRAM > 8) Copy U-Boot to RAM > 9) Perform relocation adjustments to in-RAM copy > 10) Jump to in-RAM copy > 11) Continue initialisation > >> memory, but we do have things which can speed it up. But d-cache >> matters more than just about anything.
Yes I went through these carefully at the time - remember the discussion about board_init_f_r()? I hope we can do something similar on generic board, but of course in general there is a trade-off between the time to set up the MMU tables and the time to do the copy. > > Now it may be the case (going by Wolfgang's comments) that some amount of > high-memory needs to be reserved, and the amount to be reserved is not > known until environment has been read. So there may be a need to put > the initial in-RAM stack and global data somewhere 'safe' while high- > memory space is calculated and U-Boot copied into RAM. Stack and global- > data can then be moved again (stack probably doesn't need moving, just > re-initialised at a new location) just below U-Boot. This would still be > a lot cheaper than copying U-Boot with D-Cache off Yes. With a chance of 'epsilon' of this patch getting in, I am dropping it. While I agree what you have done is much better than what was there, I have my eyes on the higher goal of unifying the board init code for all archs. Will revisit when/if generic board goes into mainline. If you have time, please take a look at that series. Regards, Simon > > Regards, > > Graeme _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
