iMX6 PCIE IRQ not working with ath9k based Wifi

[Mike Tubby]

On 10/9/2017 3:53 PM, Tim Harvey wrote:
> On Mon, Oct 9, 2017 at 5:21 AM, Lucas Stach <l.stach at pengutronix.de> wrote:
>> Hi Mike,
>>
>> Am Montag, den 09.10.2017, 12:56 +0100 schrieb Mike Tubby:
>>
>> [...]
>>
>>> If I understand correctly the ath9k driver in kernel 4.1.15 we're
>>> using
>>> doesn't enable MSI - so I assume that there is some backwards
>>> compatibility mode that then is not working because MSI is enabled
>>> at
>>> the CPU end, and hence the patch you referred to is used to turn this
>>> off.
>>>
>>> At the same time on the mailing list:
>>>
>>> https://www.mail-archive.com/ath9k-devel@lists.ath9k.org/msg14332.htm
>>> l
>>>
>>> which is part of:
>>>
>>>       https://wireless.wiki.kernel.org/en/users/Drivers/ath9k
>>>
>>> there is talk of a patch to the ath9k driver to properly implement
>>> MSI
>>> in the updated driver in kernel 4.6
>>>
>>> So, for us the question is which way to head:
>>>
>>>       a) disable MSI at the CPU and try to use legacy; or
>>>
>>>       b) update the ath9k driver to try and enable MSI ?
>>>
>>>
>>> We will also check the DTS/DTB in case something is mis-assigned.
>> Due to a design flaw of the DWC host controller, legacy IRQs (like the
>> ones used by ath9k) won't work if any MSIs are enabled on the
>> controller.
>>
>> You can take a look at my series "[PATCH 0/3] DWC host without MSI
>> controller", which works around this, but still needs some rework for
>> mainline.
>>
>> Regards,
>> Lucas
> Mike,
>
> Yes, this is exactly the scenario I keep pointing out. The ath9k
> card/drivers requires legacy interrupts which won't work when MSI is
> used on the DWC host controller used on the IMX6. I don't know what
> other cards/drivers require legacy interrupts... perhaps they are not
> that popular as this issue has lingered for a while.
>
> The patch series Lucas created disables MSI via the device-tree for
> IMX6 and is what you need: https://patchwork.ozlabs.org/cover/806603/.
> The patch series is not accepted yet and will be tweaked a bit (to do
> the same for the other SoC's that use the DWC controller, not just
> IMX6) but for IMX6 it works fine on top of a 4.13 kernel.
>
> I see from your original post you are using a 4.1 kernel. For Linux
> 4.6 and prior you can disable MSI at kernel build time but from 4.7
> onward it takes a bit more hacking.
>
> Tim

Hi Tim,

Thanks for the reply.

We're using the 4.1.15 kernel because its what we were given in the 
BSP.  I note that NXP/Freescale now have a 4.9.11 kernel officially 
supported - I'm just downloading it to have a look at.

I've also found a Qualcom provided update to the ath9k driver to add MSI 
support:

     https://patchwork.kernel.org/patch/9971077/

which is only 2 weeks old - so perhaps they've finally got round to 
fixing it as well and perhaps we can use MSI with the ath9k and not go 
around disabling it all over the place ;-)

I would be interested if you can get a 4.9.11 or later kernel going with 
the updated ath9k driver and using MSI ...

Mike