Loading FPGA ITB from EXT4 partition via SPL (A10)

Boot
1

Hi all. Does anyone know if the SPL has support for loading an FPGA (.itb) file from an EXT4 filesystem?

I have modified the <u-boot_recipe>-u-boot.dtsi so that the SPL picks up my fit_spl_fpga.itb from the /boot partition of my rootfs located on partition 3, which is a EXT4 filesystem:

fs_loader0: fs-loader {
u-boot,dm-pre-reloc;
compatible = “u-boot,fs-loader”;
phandlepart = <&mmc 3>;
};

&fpga_mgr {
u-boot,dm-pre-reloc;
altr,bitstream = “/boot/fit_spl_fpga.itb”;
};

It seems to be able to program the peripheral fine, but once it tries to program the core it fails almost instantly, giving me a fs_devread %s read error - block

Does anyone have any experience with this? Is it possible?
It doesn’t seem like the SPL has support for reading from an EXT4 filesystem, whereas u-boot does.

U-boot version: u-boot-socfpga 2020.07

I’d appreciate any help or insight. Thanks.

2

I have no experience with A10 or itb files, but I’m sure you’ve looked at this link.

Just curious, why it needs to be ext4. Wouldn’t it be just as easy to write and read from fat?

3

I have dual-image functionality i.e two rootfs on two separate ext4 partitions. I’d like the SPL to pick up the FPGA from the image I’m booting into.

4

Again, without any knowledge of Arria 10 devices, can you load it from u-boot instead using a script that can be modified based on which ext4 partition you want to load it to? i.e. instead of modifying the device tree, just change the u-boot script?

I’m not sure about itb files, but on Cyclone V you can load rbf files in u-boot from fat using something like:

fatload mmc 0:1 0x3000000 sdr.rbf
fpga load 0 0x3000000 0x700000
5

For Arria 10, the FPGA is split into a peripheral and core section and the SPL must program at least the peripheral (DDR and IO initialization). It can also program the core (core FPGA design), or you can alternatively wait until u-boot to program the core using a script as you suggested.

However, ideally what I would like is to be able to have one .itb file (with core + peripheral) for each rootfs on an EXT4 partition. The SPL would then pick up the correct FPGA depending on which rootfs I’m booting into.

I could have one peripheral .itb file in a FAT partition that the SPL could load, and then in u-boot pick up the correct core from either rootfs BUT, the core and peripheral must be a matched pair i.e the one peripheral .itb file in the FAT partition would be out of sync with one or both of the core FPGA images on the ext4 partitions.

6

Thanks for explaining, that’s very interesting. I had a look around and it looks like ext4 support is enabled by setting this flag:

Have you enabled this when generating the SPL?

PS: I tried looking for a dev board with the Arria 10. Dam things cost an arm and a leg! Must be used for some super-speciality stuff.

7

Yes I have this config option set, and looking at Kconfig it states that the SPL should be able to load u-boot or Linux from an EXT4 partition:

But no mention of loading an FPGA. I haven’t seen anyone trying to do this anywhere as of yet so I’m just curious to see if anyone has!

Thanks.

8

Random shot in the dark - does it fail if you put the itb file in the root folder of the ext4 partition? i.e. instead /boot?

9

Yes same result! It was one of the first things I tried :laughing:

10

Ugh - sorry about that. I don’t have any other suggestions, I’ll shut up now.

I am curious if you ever do figure it out. It looks like a simple thing that should be doable but not sure where the problem could be. Good luck!

11

No problem, thanks for your suggestions.

I’ll be sure to report back if I figure it out. It is surely possible, just missing something!

12

Why don’t you let the u-Boot TPL load the core using something like below?

ext2loadfs mmc 0:3 ${addr} /boot/your_itb_file.itb
fpga loadmk 0 ${addr}:core-rbf-1

If you want to change the peripheral location without rebuilding the preloader, there appears to be some “secret” environment variables that might let you reference a different device /location (looking at fs_loader.c) if you remove them from the u-Boot device tree.

storage_interface=mmc
fw_dev_part=0:3

Using environment, you could let the uBoot TPL also use the same variables to force both SPL and u-Boot to reference the same partition…

I’ve not tried them, but it might help.

-Mike

13

I don’t make use of the TPL, just SPL → u-boot → Linux. Is there a benefit to having the TPL load the core instead of u-boot? I just don’t know much about the TPL as I haven’t had to use it.

-RD

14

Sorry, the terminology I have is the TPL (third program loader) is u-Boot running out of DRAM, the SPL (secondary program loader) is the what used to be called the “pre-loader”, running out of SRAM. u-Boot is much faster at accessing data for programming, so is desirable for CORE loading.

I think we are talking the same thing.

-Mike

15

Yeah my knowledge/experience with the TPL is pretty much non-existent!

But, I do think what you are suggesting is what I am currently doing in u-boot. I am deferring the programming of the core until I am within u-boot i.e more suitable for faster programming (and can handle loading bigger files, such as the core .itb, from an EXT4 partition). The SPL doesn’t seem to be able to successfully load files any bigger than ~300-400KB from an EXT4 partition. This is not an issue if the SPL is loading bigger files from FAT, the support seems to be there. Hence the reason for this thread, just to see if anyone else had tried this.

However, as we discussed in your thread (Arria10 u-Boot 2021.04 support reboot from linux - #3 by mawillia), I am actually quite happy with the SPL loading the peripheral, and u-boot loading the core, as it is more efficient.

Thanks,
-RD