[SOLVED] How to fix the non-stop flow of mmc/mmc2 "Controller never released inhibit bit(s)" errors while booting Ubuntu Linux / LinuxMint on a Poulsbo chipset based laptop/desktop - tested on a MSI X320 laptop running Ubuntu 14.04

NOTE: Though this was originally tested on an MSI X320 laptop running fresh Ubuntu 14.04, it should work fine for other Ubuntu/LinuxMint versions as well.

If you used this fix on some other model/make, please let me know the result, and your laptop model/make using the Comments box below. Thanks!

Step 1:

First, run the following commands in Terminal to add the necessary blacklist lines:

sudo cat >> /etc/modprobe.d/blacklist.conf << EOF

# Blacklist the SDHC / MMC reader on Poulsbo devices
blacklist sdhci
blacklist sdhci-pci
blacklist sdhci_pci
blacklist mmc0
blacklist mmc_core
blacklist mmc_core
EOF

Then run the following command to update initramfs:

sudo update-initramfs -u

Step 2:

Then we have to open up the grub defaults configuration file, and change the line that starts with GRUB_CMDLINE_LINUX_DEFAULT= to add the following values to it: sdhci.blacklist=yes sdhci_pci.blacklist=yes sdhci-pci.blacklist=yes mmc0.blacklist=yes mmc_core.blacklist=yes mmc-core.blacklist=yes.

For doing that, you can use the following commands:

current_value=`sed -n -e '/^GRUB_CMDLINE_LINUX_DEFAULT/p' /etc/default/grub | awk -F'"' '{print $2}'`

new_text='GRUB_CMDLINE_LINUX_DEFAULT="'$current_value' sdhci.blacklist=yes sdhci_pci.blacklist=yes sdhci-pci.blacklist=yes mmc0.blacklist=yes mmc_core.blacklist=yes mmc-core.blacklist=yes"'

sudo sed -i "s/^GRUB_CMDLINE_LINUX_DEFAULT.*/$new_text/" /etc/default/grub

After making that change, update grub with the following command:

sudo update-grub

Now reboot the system, and the error should be gone for good.

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P.S.: If you want to run the above from a separate Live environment, you will have to first mount the necessary system folders, and then chroot to the mounted root, with the following commands, after which you can run the above listed commands:
(The following commands are given, for an example case where the installation to be modified is on /dev/sdb2. Modify that accordingly to match the partition on your machine).

mount /dev/sdb2 /mnt
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt

Then run the previously mentioned commands to fix the issue on the instance.

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Happy Computing!!!