MMC0 error

Installation Home Assistant OS
1

Hello everyone,

I have recently installed HAOS (Generic x86-64 image) directly on a Mini PC, and I am seeing constant critical errors and register dumps in my system logs:

2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x0000a402
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Blk size:  0x00000000 | Blk cnt:  0x00000000
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000000
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Present:   0x000f0000 | Host ctl: 0x00000001
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Power:     0x0000000f | Blk gap:  0x00000000
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x0000f447
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Timeout:   0x00000000 | Int stat: 0x000c8000
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Int enab:  0x00ff0003 | Sig enab: 0x00ff0003
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Caps:      0x67ea64b2 | Caps_1:   0x00000000
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Cmd:       0x0000371a | Max curr: 0x00000001
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Resp[0]:   0x00000000 | Resp[1]:  0x00000000
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Resp[2]:   0x00000000 | Resp[3]:  0x00000000
2026-06-17 08:45:38.927 homeassistant kernel: mmc0: sdhci: Host ctl2: 0x00000000

My Setup:

  • Hardware: Mini PC SOYO Y5PLUS (Intel Core i7-4650U, 8GB RAM, 256GB M.2 SSD)
  • Installation Type: HAOS (Home Assistant OS for x86-64) installed bare-metal on the internal SSD.

The system is up and running, but these lines keep flooding the log. Since this is an x86 Mini PC and NOT a Raspberry Pi, I suspect this mmc0 controller issue is related to the built-in MicroSD card reader on the motherboard, which is not on the board at all.

Questions:

  1. Is there a known bug with the generic x86-64 sdhci driver and certain Chinese Mini PC card readers?
  2. Is it safe to ignore these log entries, or could it indicate that my primary M.2 SSD is being recognized as an MMC device by mistake?
  3. Is there a way to disable the mmc/sdhci module or blacklist the built-in card reader in HAOS via cmdline.txt / grub to stop the log spam?

Thanks in advance!

2

Are you running on an SD card? If so I suspect the card itself.
An SD card is not meant for the constant writes that the HA database needs to do, and is the by far #1 failure point when people use RasPI based servers.
If you are trying to use an SD card on this mini PC, don't. Connect an SSD or even HDD to that thing and use that instead.

3

No, it's written above.

4

I would check that. That is if it came with the pc. It may just be a emmc in disguise.

5

56316
563161920×2560 1.4 MB

56317
563171920×2560 1.07 MB

I think this is a normal SSD, even though it is an ultra-budget one.

6

Yup, look like a m.2 ssd.
Could run a speed test on the drive to determine that it's true.

Search Google for "how to tell a emmc in disguise as a M.2 SSD" well give some suggestions.

7

I did a search on the nand chip "k9ckgy8h5a".
It comes up as a Samsung chip.
I highly doubt that. As this is a no named brand.

Have a look at this drive https://www.aliexpress.com/i/3256809755030853.html .
It's and ssd format but has the same chips as the m.2 in the pc.

8

Get OS access on your HAOS and then edit /mnt/boot/cmdline.txt via vi /mnt/boot/cmdline.txt and append this

module_blacklist=sdhci,sdhci_pci,sdhci_acpi

For example

console=ttyS0 console=tty1 module_blacklist=sdhci,sdhci_pci,sdhci_acpi

Reboot and see if that solves your issue. Verify the args are applied via cat /proc/cmdline.
To test this temporarily you can also just press e at the bootloader screen and append it there.

9

It's definitely not the SSD, I installed a different one and the problem persists.

10

I did it, checked it, and the problem remained.

11

It was noticed that the error spam continues for 600 seconds, after which it stops (timer?)

12

Please share the output of cat /proc/cmdline as well as the whole host logs from when the spam start and ends. It's possible this module is compiled in and thus won't work. There's apparently quirks you can apply but I'm not comfortable suggesting args I don't understand. Have you checked if there's an option in the UEFI related to it?

13 
2026-06-18 00:51:28.488 homeassistant systemd[1]: systemd-hostnamed.service: Deactivated successfully.
2026-06-18 00:51:28.663 homeassistant systemd[1]: systemd-timedated.service: Deactivated successfully.
2026-06-18 00:51:39.590 homeassistant kernel: mmc0: Timeout waiting for hardware cmd interrupt.
2026-06-18 00:51:39.590 homeassistant kernel: mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x0000a402
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Blk size:  0x00000000 | Blk cnt:  0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Present:   0x000f0001 | Host ctl: 0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Power:     0x0000000f | Blk gap:  0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x00007d07
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Timeout:   0x00000000 | Int stat: 0x00018000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Int enab:  0x00ff0003 | Sig enab: 0x00ff0003
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Caps:      0x67ea64b2 | Caps_1:   0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Cmd:       0x00000502 | Max curr: 0x00000001
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Resp[0]:   0x00000000 | Resp[1]:  0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Resp[2]:   0x00000000 | Resp[3]:  0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: Host ctl2: 0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: ADMA Err:  0x00000000 | ADMA Ptr: 0x00000000
2026-06-18 00:51:39.591 homeassistant kernel: mmc0: sdhci: ============================================
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: Timeout waiting for hardware cmd interrupt.
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: ============ SDHCI REGISTER DUMP ===========
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Sys addr:  0x00000000 | Version:  0x0000a402
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Blk size:  0x00000000 | Blk cnt:  0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Argument:  0x00000000 | Trn mode: 0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Present:   0x000f0001 | Host ctl: 0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Power:     0x0000000f | Blk gap:  0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Wake-up:   0x00000000 | Clock:    0x00007d07
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Timeout:   0x00000000 | Int stat: 0x00018000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Int enab:  0x00ff0003 | Sig enab: 0x00ff0003
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000001
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Caps:      0x67ea64b2 | Caps_1:   0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Cmd:       0x00000502 | Max curr: 0x00000001
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Resp[0]:   0x00000000 | Resp[1]:  0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Resp[2]:   0x00000000 | Resp[3]:  0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: Host ctl2: 0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: ADMA Err:  0x00000000 | ADMA Ptr: 0x00000000
2026-06-18 00:51:51.366 homeassistant kernel: mmc0: sdhci: ============================================
2026-06-18 00:51:58.485 homeassistant systemd[1]: Started Journal Gateway Service.
2026-06-18 00:51:58.493 homeassistant systemd-timesyncd[514]: Network configuration changed, trying to establish connection.
2026-06-18 00:51:58.501 homeassistant systemd-timesyncd[514]: Network configuration changed, trying to establish connection.
2026-06-18 00:51:58.514 homeassistant systemd-timesyncd[514]: Network configuration changed, trying to establish connection.
2026-06-18 00:51:58.548 homeassistant systemd-timesyncd[514]: Network configuration changed, trying to establish connection.
2026-06-18 00:51:58.589 homeassistant systemd-timesyncd[514]: Contacted time server 162.159.200.123:123 (time.cloudflare.com).
➜  ~ cat /proc/cmdline                                                                    
BOOT_IMAGE=(hd0,gpt2)/bzImage root=PARTUUID=8d3d53e3-6d49-4c38-8349-aff6859e82fd rootwait zram.enabled=1 zram.num_devices=3 systemd.machine_id=0332da1fa16a440b93c9ad847c2e2177 fsck.repair=yes module_blacklist=sdhci,sdhci_pci,sdhci_acpi console=ttyS0 console=tty0 rauc.slot=A
➜  ~

I checked the BIOS. It's very limited in functionality, and there's no option to disable the SD card.

14

Does anyone else have any suggestions?