On Thu, Aug 21, 2008 at 3:43 AM, David Jander <[EMAIL PROTECTED]> wrote: > On Thursday 21 August 2008 01:24:46 Laxmikant Rashinkar wrote: >> Hi, >> >> I have an embedded PowerPC (MPC8347) board that works fine with uboot and >> Linux 2.6.15. >> >> I am trying to upgrade the kernel so that it runs on the latest release - >> Linux 2.6.27. So far, I have gotten the kernel to compile on my platform, >> but of course it does not boot. > > Well, honestly I don't know where to look for information either (other than > the source-code and examples from others), but here is a list with points to > look out for (I have just done the same thing as you for a MPC5200B-based > board): > > 1. Upgrade to latest u-boot first (recent git seems to be fine). There have > been a lot of changes in u-boot lately about OF and device-tree related > things. I suspect you need a fairly recent version of u-boot to go well with > the latest kernel. It's also generally a good idea IMHO.
You don't *have* to do this though. There is a target called 'cuImage.<myboard>' which will embed the device tree blob in the kernel image and is backwards compatible with older u-boot versions. See arch/powerpc/boot/Makefile and arch/powerpc/boot/wrapper to see how this is generated. There is a new document that might help in Documentation/powerpc/bootwrapper.txt > 2. I assume you are porting to arch/powerpc (the old arch/ppc you used back in > 2.6.15 is obsolete and broken now). Not just broken; completely removed! :-) > 3. Look at other platforms that use the same processor, and pick a simple one > as starting point. Look out for the dts (device-tree-source file in > arch/powerpc/boot/dts), copy and modify one to reflect your hardware. > Recently a lot of changes happend in the kernel, changing device names, > obsoleting "device-type" tags, etc..., so some of the current DTS sources > included in the kernel might not even work (wrong device name, missing > information, wrong use of "device-type", etc...), so watch out for these kind > of issues too. The goal is *not* to break existing device trees because we do not know what has been deployed already and it some cases it is not feasible to update the device tree on a device. So, even though conventions have been refined and changed, backwards compatibility with older trees is supposed to be preserved. 3b. Once you've written your device tree, post it to the [EMAIL PROTECTED] mailing list and ask for review. > 4. Be sure that the device(s) necessary to produce output on your console are > correctly placed in the DT. Also make sure that u-boot knows about it > (#define OF_STDOUT_PATH... in your u-boot board config file) > > 5. When compiling the device tree, it may be necessary to add some extra > reserved entries to the compiled tree (I am using dtc -p 10240 -R 20, which > might be slightly exaggerated), because u-boot may add something to it, and > if it can't, linux won't boot. > > 6. Remember to always specify the "rootfstype=" option on the commandline if > booting from anything other than NFS. This was not necessary back in the > 2.6.15-times AFAICR. > > 7. Boot with a device-tree (in u-boot: "bootm $addrofkernel - $addrofdtb", > don't forget the dash if you are not using an initrd). If you don't do this, > u-boot can't fix your DT, and the kernel probably won't find it either. > > 8. Be sure to use the correct version of the DTC (DT compiler) for your kernel > (the sources are included nowadays, somewhere in arch/powerpc/boot IIRC). The > command used to compile, should probably be something like this: > > $ ./dtc -p 10240 -R 20 -I dts -o myplatform.dtb -O dtb -b 0 dts/myplatform.dts There is a makefile target now to help you with this and pass the right options for reserving entries: $ make myplatform.dtb The dtb image will appear in arch/powerpc/boot > Load the resulting .dtb file directly with u-boot (don't make an u-image out > of it). > > That's all I remember right now... hope it helps. > > Regards, > > -- > David Jander > _______________________________________________ > Linuxppc-embedded mailing list > Linuxppc-embedded@ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-embedded > -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. _______________________________________________ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
