On 10/02/2012 13:28, Marek Vasut wrote: >> Hi, >> >> because we are fast able to boot the kernel directly from SPL, I am >> experimenting now how we can speed up the process. Mainly my focus is >> how to make copy from storage (=NAND) to RAM faster. >> >> There are two approaches I can see: using DMA in NAND driver, or/and >> enabling cache. I have not yet patches (I hacked the code dirtly), but I >> have some results I cannot understand. >> >> First of all, DMA. DMA for OMAP is mainlined now with Simon's patches, >> enabling DMA in nand_spl_simple.c as sent by Simon does not work for me, >> but I have adapted the patch to my platform (twister board, mainlined, >> with TI AM3517). Here the results measuring between start of the copy >> and before giving the control to the kernel (kernel size is 2188100): >> >> Seconds >> ----------------------------------------------------------------- >> No cache, no DMA 1.700 >> DMA in NAND driver 1.190 >> Enabling Cache 2.120 >> >> With enabled DMA I won on my platform ~600mSec. However, enabling cache >> is worse than disabling, and this let me really confused. >> >> I have not done any special things to enable cache, and I reused code >> already provided. I have only set to an arbitrary address in RAM (but >> 64KB aligned) gd->tbl, and then I called enable_caches(). I can see that >> mmu_setup() is called, and at the end icache_status() and >> dcache_status() return both that cache is enabled. >> >> But copying from NAND takes longer enabling cache, and this does not >> really make sense. Does anybody have an hint what I am missing ? > > L2 is on too?
As far as I have understood, I can disable L2 on TI-omap3 only if I set CONFIG_SYS_L2CACHE_OFF, and this is not my case. And there should be then any apparent difference between SPL and U-Boot by enabling the cache (I mean, if L2 is off, is off also in u-boot). When U-boot runs, I see only that enable_caches() is called after setting the page tables, and that is enough in u-boot to get dcache working. I did the same in SPL, but it seems really something is missing... Stefano -- ===================================================================== DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: [email protected] ===================================================================== _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
