Re: Barebox for Zedboard

[Johannes Roith <johannes@gnu-linux.rocks>]

Am Mon, Mar 23, 2020 at 03:18:22PM +0000 schrieb Michael Graichen:
Hi Michael, hi Lucas,
> 
> ________________________________________
> Von: Lucas Stach <l.stach@pengutronix.de>
> Gesendet: Donnerstag, 19. März 2020 11:53
> An: Michael Graichen; barebox@lists.infradead.org
> Betreff: Re: Barebox for Zedboard
> 
> Hi Michael,
> 
> Am Donnerstag, den 19.03.2020, 10:38 +0000 schrieb Michael Graichen:
> > Hey,
> >
> > i have just started working on a Zedboard (http://zedboard.org/product/zedboard) with an Xilinx Zynq XC7Z020 SOC.
> > I have seen that Barebox has an defconfig for the zynq
> > so i tried
> >
> > export ARCH=arm
> > export CROSS_COMPILE=arm-cortexa9-linux-gnueabihf-
> > export PATH=/opt/OSELAS.Toolchain/arm-cortexa9-linux-gnueabihf/bin:$PATH
> > make zynq_defconfig
> > make -j`nproc`
> >
> > which compiles me the image
> >
> > barebox-flash-image -> images/barebox-avnet-zedboard.img
> >
> > when using u-boot i had to generate a BOOT.bin file with Xilinx's ./bootgen tool
> >
> > dev$ bootgen -image bootimage.bif -o i BOOT.bin
> >
> > and .bif file was
> >
> > dev$ cat bootimage.bif
> > //arch = zynq; split = false; format = BIN
> > the_ROM_image:
> > {
> >      [bootloader]FSBL.elf
> >      design_1_wrapper.bit
> >      u-boot.elf
> > }
> >
> >
> > that i copied onto an SD-Card and powed up the board.
> >
> > But since i want to use Barebox how do i produce the BOOT.bin file?
> 
> The barebox-avnet-zedboard.img already is the BOOT.bin image, just copy
> it to the SD card with this name and you are done.
> 
> > and how is the programming of the FPGA Logic done?

Michael, did you implement something here? In the latest barebox version
I can't find anything related to FPGA loading. But if you have developed
something and you could share it, it would be interesting for me and 
highly appreciated.

> 
> Barebox currently doesn't support loading the FPGA bitstream. We are
> still lacking a driver for the DevC PCAP interface. Zynq support in
> Barebox is only a spare time (and thus toy) project at this time. It
> works okay for booting Linux on the PS part of the system, but almost
> fully lacks support for the PL part.

I would like to try bringing PL support to barebox, but I need a bit of
guidance. In the Linux kernel there are drivers available for the ZYNQ
FPGA and there is the FPGA manager. As barebox "reuses" Linux drivers
maybe that would be the way to go.

I would love to have one barebox command available to load a bitstream
to the PL. For doing so I would need to implement a fpgamgr-lib where I
provide the interfaces used by the Linux FPGA drivers. The drivers also
need to be modified a bit. Then finally I can implement the command.

Am I missing something? Do you have any advice or sample code I could
take a look at or use for orientation? Any comments are welcome.

The big advantage of using such an approach would be support for similar
devices (e.g. the UltraScale+ ZYNQMP devices) could be added easily by
porting the Linux drivers to barebox.

> 
> That said I wouldn't mind helping with getting the missing bits added
> by reviewing/testing patches. :)
> 
> Regards,
> Lucas
> 
> Hey Lucas, 
> 
> "That said I wouldn't mind helping with getting the missing bits added
> by reviewing/testing patches. :)"
> 
> Did you made any attempts to do this?
> 
> As far as I can see there are basicly two ways.  
> The "Xilinx-Way" by packing everything in Boot.bin.
> https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18841976/Prepare+boot+image
> and the "Linux-Way"
> https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18841645/Solution+Zynq+PL+Programming+With+FPGA+Manager
> using the FPGA manager 
> https://elixir.bootlin.com/linux/latest/source/drivers/fpga/zynq-fpga.c
> 
> Best regards
> Michael
> 
> 
>  
> 
> 
> 
> 
> 
> _______________________________________________
> barebox mailing list
> barebox@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/barebox

Best regards,
Johannes