Current unstable-nios2mmu (v2.6.38) running on Nios2 without MMU

[Altera_Forum]

[this is a "cross-post" from the nios2-dev mailing list. Sorry for the noise to anyone following both.] 

 Hi all  With today's release of Linux Kernel 2.6.38 I thought it might be a good idea to put the final few bits together, needed to get the current Nios2 Linux Kernel port running on Nios2 without MMU too and as you can see below I was successful :-)  root:/> cat /proc/version  uClinux version 2.6.38-01035-g22583a7-dirty (tklauser@fermion) (gcc version 3.4.6)# 9 Tue Mar 15 15:40:49 CET 2011 root:/> cat /proc/cpuinfo  CPU: Nios II/fast MMU: none FPU: none Clocking: 50.00 MHz BogoMips: 23.04 Calibration: 11520000 loops HW:  MUL: yes  MULX: no  DIV: yes Icache: 4kB, line length: 32 Dcache: 2kB, line length: 32 root:/>   There are a few caveats though:  - Due to a bug in the handling of the __builtin_constant_p builtin in  the GCC version used for Nios2 NOMMU, a patch to kernel/sched.c is  needed [0].  [0] http://distanz.ch/nios2-linux/0001-omit-use-of-ilog2-macro-in-kernel-sched.c-for-nios2-.patch  - Quite a few options from the kernel and the userspace configuration  needed to be disabled (e.g. the whole block layer, the boa  webserver and others). You can find the configuration I used at [1].  I used a linked in device tree, so you need to adjust the path in  CONFIG_DTB_SOURCE to where your dts file lies.  - I didn't really stress test the running system yet. I also wasn't  able to get a network connection yet due to the missing device tree  support in the altera_tse driver.  - As recently announced by Thomas, the kernel now only runs with device  tree (it might still with the old board layer, but I doubt it and  didn't test it). Though you still need to adjust a few values in  arch/nios2/boards/generic-dts/include/asm/nios2.h to the values from  your generated custom_fpga.h.  [1] http://distanz.ch/nios2-linux/nommu_defconfig/  So as you see there are still some odds and ends to it, but we'll hopefully sort these out in the next few weeks. Also there is quite a bit of potential to unify some parts of the code even more (e.g. the whole cacheflushing)  I'd be glad for anyone interested in this to test the Kernel on their designs/boards and let us know any problems (patches prefered of course ;-). So here's what you need to do in order to get the NOMMU kernel running:  1) Prepare a SOPC design with a Nios2 w/o MMU (I took the MMU reference  design from the wiki, adapted it to our board and additionaly added a  watchdog timer and a sysid component).  2) Generate a dts file from your design using the sopc2dts tool. See  the [2] in the Altera Wiki for reference.  3) Pull the latest unstable-nios2mmu from the linux-2.6 repository on  sopc.et.ntust.edu.tw (tagged as v2.6.38-nios2) and check it out to a  local branch. Check out the trunk branch of the uClinux-dist repo.  4) Apply the patch from [0] to your Linux kernel sources.  5) Download the config.linux-2.6.x and config.vendor-2.6.x from [1] and  put them to vendors/Altera/nios2nommu in your uClinux-dist.  6) Select Altera/nios2nommu in the vendor/product selection, select  "Default all settings (lose changes)"  7) Set CONFIG_DTB_SOURCE in the kernel configuration to the generated  dts file.  8) Optional: Change the console to the JTAG UART.  9) Build your kernel, download your design and kernel and hopefully see  it boot :-)  [2] http://www.alterawiki.com/wiki/devicetree  That should be it, I hope I didn't forget anything and sorry for the lenghty email. I'll also post these instructions to the forum.  Cheers Tobias