Hi All, I am trying to boot linux on lowRISC using a custom Virtex-7 board. Unfortunately, the SD card interface has some issues and I am unable to use it. I was able to bring up the lowRISC design and run hello world and dram test successfully. Since, I do not have the SD Card, I tried to load the BBL directly on to DDR using the custom AXI interface provided by the board vendor. It loads successfully and a few debug prints from the BBL also show up on the UART terminal. I had to modify the boot.c code inorder to get this working. Going forward, I was curious to know if I can load the vmlinux and root.bin also to DDR and boot linux. I understand that the base address for vmlinux is fixed to 0x80000000+OFFSET. Will it be possible for me to change this and boot linux directly from DDR ? Thanks & Regards, Anup Kini.

Thank You Jonathan for the explanation. It looks rather cumbersome to go ahead with this option. I looked at the Flash & Jump baremetal examples in v0.5. I was wondering if we could use the onboard 1Gbit QSPI Flash in place of the SD Card. I tried to load the VMLINUX and BBL file directly using Xilinx Hardware Manager, but the tool expects a bin file. Something similar to zImage for ZYNQ. is it possible to boot lowRISC using the onboard QSPI Flash? Thanks & Regards, Anup Kini. On Mon, Mar 19, 2018 at 4:09 PM, Dr Jonathan Kimmitt <jrrk2(a)cam.ac.uk <mailto:jrrk2@cam.ac.uk>> wrote: It's possible to change the base address of RAM in Linux from 0x80000000 but this has an impact on page tables, Berkeley boot loader, spike simulator and chisel etc. You might find it easier to modify your custom AXI interface address if that is possible. Alternatively if you have dynamic memory on board your card, you could adapt the Xilinx MIG config to use this memory and save the overhead of the custom AXI interface. Most cards come with an example MIG config to reduce the burden of setting all the parameters correctly. If you want to have a go at changing the kernel address, you need to be aware that it is BBL that loads at 0x80000000 and not the kernel itself. Typically the kernel address will be loaded at the next megapage which is typically 0x80200000. And the kernel never accesses this address because it runs in supervisor mode which sets the kernel address to 0xffffffff80000000 using the MMU. If you change the base address you need to make sure any calculations involving BBL address or MMU page tables are corrected. All very simple NOT! On 19/03/18 06:57, Anup Kini wrote: Hi All, I am trying to boot linux on lowRISC using a custom Virtex-7 board. Unfortunately, the SD card interface has some issues and I am unable to use it. I was able to bring up the lowRISC design and run hello world and dram test successfully. Since, I do not have the SD Card, I tried to load the BBL directly on to DDR using the custom AXI interface provided by the board vendor. It loads successfully and a few debug prints from the BBL also show up on the UART terminal. I had to modify the boot.c code inorder to get this working. Going forward, I was curious to know if I can load the vmlinux and root.bin also to DDR and boot linux. I understand that the base address for vmlinux is fixed to 0x80000000+OFFSET. Will it be possible for me to change this and boot linux directly from DDR ? Thanks & Regards, Anup Kini.