ath10k + INTEL_IDLE aka. cstates == firmware crash

[Michal Kazior]

On 23 February 2015 at 14:44, Fabian Wittenberg
<Fabian.Wittenberg at sophos.com> wrote:
> Hi Michal,
>
> I used firmware version 10.1 and 10.2 from here:
> https://github.com/kvalo/ath10k-firmware. Both show the same behavior.
>
> You are right. There are some BIOS that do strange handling of this
> cstate stuff but we have no influence on the BIOS as this is done by
> our hardware vendor. We experimented a lot with the MSI masking bit of
> the pci-e root bridge where the ac-card is connected to.
> There were no remarkable improvements playing around with this bit.

If you don't have BIOS/UEFI upgrade available you can try appending
`intel_idle.max_cstate=0` to kernel boot parameters. Keep in mind this
will disable CPU power management.


> We have tested the same boards with cards that need ath9k as well. They
> are working just fine. With and without enabled INTEL_IDLE...

I run with my laptops (i5-3320M and  i5-2520M) with INTEL_IDLE and QCA988x fine.

I'm not really an expert on this stuff but since C-state alter some
voltages perhaps the Atom SoC has some deviations/instabilities in
voltages which prevent some quirky devices like QCA988x from working
reliably.


Michał