On 02/18/2015 09:35 AM, menon.nisha...@gmail.com wrote: > On Wed, Feb 18, 2015 at 7:12 AM, Vitaly Andrianov <vita...@ti.com> wrote: >> >> >> On 02/17/2015 05:47 PM, Nishanth Menon wrote: >>> >>> On Tue, Feb 17, 2015 at 4:27 PM, Murali Karicheri <m-kariche...@ti.com> >>> wrote: >>>>>> >>>>>> is complete the boot-loader sets the PC to the first MSMC address >>>>>> 0x0c000000. The u-boot.bin is linked to the address 0x0c001000. >>>>> >>>>> >>>>> why not just shift u-boot.bin to start of MSMC address? >>>> >>>> >>>> What is wrong with the current implementation? NAND and SPI NOR boot >>>> modes >>>> use the >>>> GPH headers that has the load address defined. But in the case of UART, >>>> RBL >>> >>> >>> So it GPH header has the load address defined, it does mean that we >>> could infact change the start address to 0xc000000 (instead of current >>> 0xc001000) and appropriately update the GPH headers to point there? >>> that way we can use 0xc000000 without padding on UART, as well as use >>> the same in NAND/SPI as well? correct? >>> >>>> loads it to start of MSMC and adding 1K of NOP just avoid a jump >>>> instruction >>>> at >>>> the start of the memory to jump to 0xc001000. This way we can keep the >>>> same >>>> start address across all boot modes. >>> >>> >>> Padding a 4kbytes (1K NOP at 32bits each) just because there is a >>> difference between linked address and start address in a specific mode >>> makes one wonder. This probably is not definitely a uniquely KS2 issue >>> - we probably have similar behavior on other platforms as well. what >>> if we chose a link address 2MB away (as an example)? agreed that the >>> specific usage has no such size story in place, but conceptually we >>> might be able to do better. >>> >>>>>> In order to use the u-boot.bin as an image for UART download, we need >>>>>> to >>>>>> add 4K zeros prefix that act as 1K NOP instructions before reaching >>>>>> 0xc001000. >>>>> >>>>> >>>>> OR, add a relocation logic which saves the 1k NOP and resultant load >>>>> time? >>>> >>>> >>>> What saving are you talking about? Miliseconds? seconds? >>> >>> >>> Maintainability? lets say we change link address tomorrow, we have to >>> adjust padding appropriately, further we just dont need padding when >>> we can just relocate self by being position independent in the first >>> place!. >>> >>> we have learnt that over years OMAP3 link address has gone through a >>> few transitions as we discovered better ways to do things. doing >>> padding based on link address does, on the first look, seem >>> unnecessary, makes sense only if all of the following are wrong: >>> a) cannot change start address to the common start address for all boot >>> modes. >>> b) cannot add relocation and position independent u-boot code. >>> >>> And even when we do need to add padding, it is not a good idea to hard >>> code the pad size, instead do it algorithmically (basically query the >>> start and add the delta) allowing changes to link address to be >>> something folks can do at a later point in time without >>> unintentionally breaking uart boot. >>> > [...] >> As I've already mentioned this patch is not about improving or changing >> current u-boot.bin, but just providing a way to download it over UART port. >> Any improvements, if they are required, shall be done in other patches. > > > We would not need a u-boot.uart if current u-boot.bin can do the job, do we? >
I just noticed this: http://git.denx.de/?p=u-boot.git;a=blob;f=doc/README.arm-relocation;h=645b3746c8a88fe25f7c9a33cd9b8b17aa7b5a57;hb=HEAD#l37 without relocation capability, a board might be liable for removal? -- Regards, Nishanth Menon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
