On 11/13/2013 05:14 PM, Rob Herring wrote: > On 11/13/2013 07:40 AM, Michal Simek wrote: >> On 11/13/2013 11:19 AM, Michal Simek wrote: >>> On 11/12/2013 08:42 PM, Geert Uytterhoeven wrote: >>>> Kill the microblaze-specific __fdt_blob section, and start >>>> using .dtb.init.rodata from <asm-generic/sections.h> for >>>> built-in DTBs, like most other DT enabled architectures. >>>> >>>> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Cc: >>>> Michal Simek <monstr@xxxxxxxxx> Cc: Rob Herring >>>> <rob.herring@xxxxxxxxxxx> Cc: >>>> microblaze-uclinux@xxxxxxxxxxxxxx Cc: >>>> devicetree@xxxxxxxxxxxxxxx --- Untested, but the resulting >>>> vmlinux after "make simpleImage.system" looks sane. >>>> >>>> QUESTION: The padding of the DTB is gone, is this OK? >>> >>> Removing this kernel padding should be fine. I can't remember why >>> it was there from the beginning. >> >> I know why is this here. The reason is process how dtb is passed to >> the kernel via command line. head.S code just copy that dtb to the >> same location where compiled-in dts is expected and kernel doesn't >> need to care about position of dtb because this copy is done >> without MMU. And the full kernel is covered by 2 tlbs and we don't >> need to use another TLB for dtb mapping. >> >> It means pad matters a lot. Because u-boot ITS format doesn't use >> simpleImage target but the kernel need to have a space for copying >> dtb to this kernel location. >> >> Let me think about if there is an easy way to handle dtbs which are >> passed from bootloader. > > Isn't the built-in dtb in a RO init section? Seems like a bad idea to > write to it. Also, it will be a double copy because a built-in dtb has > to be copied out of init section. Microblaze has it currently out of RO section. This patch is adding it there. I have looked at powerpc flow which is probably the closest to our version. head.S Saving dtb pointer to r31 then initial_mmu which setups 16MB tlb for kernel then some exception and calling machine_init()->early_init_devtree() ->move_device_tree() where also change initial_boot_params location for unflatten_device_tree() in setup_arch(). Ben: I didn't find any TLB entry for DTB itself. Does it mean that I missed it or that powerpc can access in machine_init() the whole memory space? Thanks, Michal -- Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91 w: www.monstr.eu p: +42-0-721842854 Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/ Maintainer of Linux kernel - Xilinx Zynq ARM architecture Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform
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