I believe you do have some serious misconceptions here.
Our carrier board design requires to be able to boot (u-boot included) from SD as a recovery precaution and I guess the proper way is to use the recovery pin available on the module.
I’m seriously wondering where you got such strange idea from but the recovery mode has definitely absolutely nothing to do with such SD boot.
In my understanding, the recovery pin is expected to trigger the Serial Downloader boot in the iMX8M
i.MX 8M Mini that is.
,so, I expect to be able to use the “SDMMC manufacture mode”.
No, the SDMMC manufacture mode is only to be used during manufacturing on un-fused completely pristine SoCs.
I also checked the DISABLE_SDMMC_MFG which seems still in default 0 value:
Verdin iMX8MM # md.l 0x30350490 1
30350490: 00000000 …
I don’t think any such masters. Anyway, I do know for sure that this SDMMC manufacture mode does actually work on completely pristine un-fused modules but even then it only works on a special carrier board resp. the Verdin Development board if the SD card power signal is bypassed.
When I power on the module (SD inserted, Recovery pressed, USB OTD disconnected) seems that nothis is loaded from the SD.
I’m using an SD Image geneated by Yocto wich seems to have a proper IVT and a proper u-boot.
Even here I do have my doubts as our regular images are eMMC fastboot images while an SD card image would likely need to be different.
As a last resort before posting I also copied the eMMC first 4MB into the SD, but still nothing on the u-boot console. When I boot from the eMMC everything is ok.
That’s exactly what I’m talking about. This is not how our modules boot. They boot from the primary eMMC hardware area boot partition in a mode which is called eMMC fastboot.