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atomic DMA coherent pool is too small error

100bobdxcool

I am running xillinux.

ERROR: 256 KiB atomic DMA coherent pool is too small!
[ 3.648517] Please increase it with coherent_pool= kernel parameter!

I get this error after I installed this driver for RT5370 chipset

I tried to create a uEnv.txt file (based on this link,
http://architechboards-microzed.readthedocs.org/en/latest/_static/uEnv.txt)
with the following content:

bootcmd=fatload mmc 0 0x3000000 uImage; fatload mmc 0 0x2ff0000 devicetree.dtb; bootm 0x3000000 - 0x2fF0000
uenvcmd=boot
coherent_pool= 4M

I added this uenv to the SD card along with uboot, device tree, etc

Still gives the same error ?

Can anyone help me on this ?

  • 0

    Hi bobby,

      This looks like a generic issue with DMA buffer allocation, and unfortunately this is really beyond the scope of what we can answer here.  If we have an existing reference design or we are working in the area, most times we can propose a solution path but in this instance we have neither.   I did a quick google search for this problem, and there are numerous references to the error on many different linux platforms, so it may be that since you are the expert on exactly what you are implementing, you can read some of the conversations that exist in the public domain and determine a probable solution path.   If you are successful, or if you even get a little farther it would be great if you could let the community know so we can increase our knowledge base.

    For example, here's an example of such a discussion for raspberry pi:

    https://github.com/raspberrypi/linux/issues/170

    As an alternative, you can try pinging the Xillinux support forum since they may also have specific experience with this issue.

    Ron