Mmc0: Failed to initialize a non-removable card on Rock 4C+

General Discussion
1

I have DietPi installed on my Radxa Rock 4C+ but booting takes 45 seconds. And running systemd-analyze does show the following:

Startup finished in 39.492s (kernel) + 6.155s (userspace) = 45.648s
graphical.target reached after 6.114s in userspace.

Userspace is really quick, but kernel is slow:

dmesg -T | grep -iE "timeout|timed out|failed|error"
[fre jun  5 10:56:34 2026] mmc0: Failed to initialize a non-removable card
[fre jun  5 10:57:15 2026] dw-apb-uart ff180000.serial: failed to request DMA

I have DietPi installed on a 64gb MicroSD, good quality Sandisk Extreme. I have a SSD connected with USB. And the MMC is empty.

It seems like it is trying to boot from the MMC even though it is empty?
Can I disable this to speed up the boot?

2

I did this in dietpiEnv.txt:
extraargs=net.ifnames=0 rockchip.disable_emmc=1
Added the rockchip.disable_emmc=1

This seems to have speed up boot to 15 seconds. But every so often I get a 45 second boot, and the error is still there even on a 15 second boot:
dmesg -T | grep -iE “timeout|timed out|failed|error”
[fre jun 5 11:26:06 2026] mmc0: Failed to initialize a non-removable card
[fre jun 5 11:26:16 2026] dw-apb-uart ff180000.serial: failed to request DMA

What’s a permanent fix to make sure i get quick boot times?

3

you might need to check the entire chain during boot process to see where time is lost

systemd-analyze critical-chain

Maybe there are other processes involved as well

4 
systemd-analyze critical-chain
The time when unit became active or started is printed after the "@" character.
The time the unit took to start is printed after the "+" character.

graphical.target @5.950s
└─multi-user.target @5.949s
  └─ntpsec.service @5.851s +88ms
    └─nss-lookup.target @5.844s
      └─dnsmasq.service @5.429s +413ms
        └─network.target @5.413s
          └─networking.service @4.268s +1.144s
            └─network-pre.target @4.242s
              └─dietpi-preboot.service @3.329s +910ms
                └─basic.target @3.254s
                  └─sockets.target @3.250s
                    └─dbus.socket @3.250s
                      └─sysinit.target @3.246s
                        └─systemd-update-utmp.service @3.212s +33ms
                          └─systemd-tmpfiles-setup.service @3.132s +59ms
                            └─local-fs.target @3.117s
                              └─run-credentials-systemd\x2dtmpfiles\x2dsetup.ser                                                                vice.mount @3.146s
                                └─local-fs-pre.target @1.456s
                                  └─keyboard-setup.service @1.134s +320ms
                                    └─systemd-journald.socket @1.105s
                                      └─-.mount @1.065s
                                        └─-.slice @1.065s

Here it is.
Do you have any idea about the mmc problem?