Comment # 38 on bug 922529 from Thomas Renninger

Ok, sorry for not looking into logs earlier.
As you can access the device later, everything is there in the linux kernel.
The question is:
1) What is missing in dracut (kernel driver)
2) What has to be done to activate and be able to access the rootfs
(possibly/hopefully nothing).

For 1. I found this in dmesg:
[   19.294260] shpchp: Standard Hot Plug PCI Controller Driver version: 0.4
[   19.371483] sdhci: Secure Digital Host Controller Interface driver
[   19.371487] sdhci: Copyright(c) Pierre Ossman
[   19.553752] mei_txe 0000:00:1a.0: irq 106 for MSI/MSI-X
[   19.614409] sdhci-pci 0000:00:12.0: SDHCI controller found [8086:0f16] (rev
e)
[   19.615623] mmc0: no vqmmc regulator found
[   19.615627] mmc0: no vmmc regulator found
[   19.616847] mmc0: SDHCI controller on PCI [0000:00:12.0] using ADMA
[   19.616878] sdhci-pci 0000:00:17.0: SDHCI controller found [8086:0f50] (rev
e)
[   19.618097] mmc1: no vqmmc regulator found
[   19.618102] mmc1: no vmmc regulator found
[   19.619299] mmc1: SDHCI controller on PCI [0000:00:17.0] using ADMA
[   19.677741] ACPI: Deprecated procfs I/F for AC is loaded, please retry with
CONFIG\
_ACPI_PROCFS_POWER cleared
[   19.677944] ACPI: AC Adapter [ACAD] (on-line)
[   19.764855] mmc1: BKOPS_EN bit is not set
[   19.829371] mmc1: new HS200 MMC card at address 0001

So (at least) these look like the relevant drivers you have to have in the
initrd:
shpchp, sdhci, sdhci-pci

So please add a file:
/etc/dracut.conf.d/05-eMMC.conf

and add this line:
add_drivers+="shpchp sdhci sdhci-pci"

then call "dracut" and restart with the newly generated initrd.

Hm, these instructions would apply for a normal installed system. Let me
re-read and think about how to test this on your live system.