How do disable MMC Command Queue Engine

What is the kernel parameter to disable the Command Queue Engine driver?

I am reading through mmc.c

MMC_DEV_ATTR(cmdq_en, "%dn", card->ext_csd.cmdq_en);
* Enable Command Queue if supported. Note that Packed Commands cannot
* be used with Command Queue.
card->ext_csd.cmdq_en = false;

I am thinking maybe setting the parameter ext_csd.cmdq_en=false
I tried this sdhci.debug_quirks=0x65168080 as mentioned here but it doesn’t work.

Asked By: Bret Joseph


It turns out the device tree has "mediatek,cqhci" property which isn’t supported well by the kernel


/ {
    mmc@11230000 {
        compatible = "mediatek,mt6768-mmc";

So I had to modify the device tree file with fdtput.

fdtput -d /path/to/fdt /mmc@11230000 "mediatek,cqhci"


  1. I dumped the device tree blob from the boot.img
  2. Binwalked the blob to get the pure flattened device tree
  3. Deleted the cqhci enabler property from the blob
Answered By: Bret Joseph
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