Hi Simon,
2014-09-06 3:59 GMT+09:00 Simon Glass <s...@chromium.org>: > Hi Masahiro, > > On 4 September 2014 23:50, Masahiro Yamada <yamad...@jp.panasonic.com> wrote: >> init_page_table > > Why do you need a full page table in this code? Can you not use the > existing page table features in U-Boot? I assume you mentioned mmu_setup() function in arch/arm/lib/cache-cp15.c. I do know it and actually my boards are using it too. The hardware specification of UniPhier platform is a little special and unfortunate in terms of RAM / Cache handling. UniPhier SoCs have no on-chip SRAM! Let's assume U-boot is booting from NOR Flash. We have to setup the stack before junping to board_f(), but there is no writable memory at this moment on our SoCs. (UniPhier has SDRAMs, of course, but it is intialized in board_f().) To solve the problem, our SoCs use a trick to have stack on L2Cache. To use cache, MMU must be turned on. (This is ARM specification) That's why hard-coded, full page table must be placed in the code. When SDRAM is available, the page table is switched to the one created in arch/arm/lib/cached-cp15.c, but which is much lator (board_r() func.) Best Regards Masahiro Yamada _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
