Hardware Linux

ath/ath9k/cfg80211 being weird (regdomain and wireless)

Upon upgrading my Kernel on my Ubuntu 20.04 LTS to the HWE stack, I ran into the issue that Wifi stopped working.

Turns out, it only refused to listen/transmit on channels 12 and higher. My router was using channel 13, so no luck.

After some research, I found that you can set the Wifi stack to obey your country’s regulatory requirements. In Germany, channels 12 and 13 are fine to use.

Others had the same problem back in the day, apparently. But the proposed solution did not work or did not work anymore.

In my case, with a Qualcomm Atheros AR93xx using ath9k, editing /etc/default/crda setting REGDOMAIN=DE or trying to use iw reg set DE did not help.

What helped after all was setting ieee80211_regdom=DE when loading the cfg80211 module. So, I somehow doubt that the issue was the ath9k module itself.

Try this:

Create /etc/modprobe.d/cfg80211.conf with content:

options cfg80211 ieee80211_regdom=DE

Obviously, you set it to the 2-digit ISO code of the place you live at.

For Germany, this results in the expected 2.4 GHz band channel list (iw list | grep -A 15 Frequencies:):

* 2412 MHz [1] (20.0 dBm)
* 2417 MHz [2] (20.0 dBm)
* 2422 MHz [3] (20.0 dBm)
* 2427 MHz [4] (20.0 dBm)
* 2432 MHz [5] (20.0 dBm)
* 2437 MHz [6] (20.0 dBm)
* 2442 MHz [7] (20.0 dBm)
* 2447 MHz [8] (20.0 dBm)
* 2452 MHz [9] (20.0 dBm)
* 2457 MHz [10] (20.0 dBm)
* 2462 MHz [11] (20.0 dBm)
* 2467 MHz [12] (20.0 dBm)
* 2472 MHz [13] (20.0 dBm)
* 2484 MHz [14] (disabled)

Hardware Linux

SATA/Soft-RAID Cards that work

A while ago, I wanted to add more space to my MD+LVM2 array on a Linux machine (Ubuntu 20.04 at the moment).
The setup used MD to make a RAID1 of two HDDs and knowing that I would eventually like to add more storage later, I put LVM2 on top.

A Card That Doesn’t Work

The moment came but I realised my mainboard did not have enough SATA ports. So, after some research, I bought a HighPoint Rocket 640L PICe SATA host adapter which comes with a Marvell 88SE92xx series chip (88SE9230 in my case).

Tl;dr: Don’t.

It took me half a day of research to figure out that (as of September 2021 and Linux kernel 5.4, but I tried 5.14 too) it would not show disks at all if IOMMU was activated. Also, it did not like stand-by/hibernation: HDD 4 would spin up fine on boot, but would not show up after a stand-by rendering the RAID incomplete, and the LVM volume in read-only mode. Which is a nice safeguard, thanks LVM-developers! But still annoying as such of course.

A Card That Does Work

So, I did more research and found the Delock 5x SATA PCIe x4 Card featuring a JMicron Technology chip (with an ID [197b:0585]). And guess what:

  • All disks come back after stand-by/hibernation
  • IOMMU and virtualisation can be switched on, no problem
  • It even has one more port than the HighPoint card

Disclaimer: All this may change in the future. I have no idea if this is a driver problem or a problem with the chip. But I though it might save some of you time.


Don’t use Marvell 88SE92xx series, at least in a Linux system. Full stop.