Raspberry Pi 4

Hmm, the whole of SPI1 is not working. There is no data at all read back, it seems.
Do you know whether data actually gets sent out? You have your own FPGA setup; maybe you can put an oscilloscope on the lines and see whether this is a read problem or a complete fail on all the SPI1 lines? That may narrow the problem down.

Also, do you have a RPi3? Now I am wondering if the older version actually still works. You should be able to swap the SD card and boot if you have not locked the kernel to the new SoC.

unfortunately I locked the kernel to the new SoC.
But i own a raspberry pi 3 and i found a image on Gene website so i'm gonna try

Just tried with a RPi3 and unfortunatly the only image that i found on Gene website is an old one (dec 2016)
HM2_rpspi seems to be really old ("spi_probe=16" is unreconized same for "spi_debug")
i have a too small oscilloscope (1 mhz max) so it will be difficult to monitor SPI1

You didn't look in the right place. Add /lathe-stf to the link in my sig, which should get you a directory containing linixcnc4rpi4, click on that and you'll find a build but not stripped kernel, and the debs that are running linuxcnc on my rpi4 and have been for a couple months. The debs ae ready to install and supposedly have Bertho's latest rpspi. driver. I couldn't make the read and write speed commands work, and my lashup will not read from a 7i90HD any faster that 25 megabits, so the code is hard built for a 31 megabit write and a 25 megabit read. Untested with the other two cards.

That kernel contains the newer much faster video drivers and will make 60 fps glxgears on a full 1920x1080 screen, which is about 58 fps faster than the older kernel can do.

Sorry the kernel is about 2.5 gigabytes but its fully built, just follow Big Johns instructions to install what you need from it.

I don't have upload bw to spare, so its slow. And I've blocked about 40 of the nets less well trained bots from mirroring my site.

And my blocks are /24 wide. So I you can't get it,, send an email to gheskett@shentel.net, containing your outside ipv4 address and I'll clear that block if you are in its /24 reach, meaning the first 3 numbers match.

Be my guest.

Thanks Gene
I'm downloading your kernel. Seems really promising.