Re: brcmfmac signal/interference issues

[Arend van Spriel <arend.vanspriel@broadcom.com>]

On 3/8/2018 4:54 PM, Steve deRosier wrote:
> On Thu, Mar 8, 2018 at 2:47 AM, Arend van Spriel
> <arend.vanspriel@broadcom.com> wrote:
>> On 2/23/2018 2:49 PM, Daniel Drake wrote:
>>>
>>> On Fri, Feb 23, 2018 at 12:54 PM, Arend van Spriel
>>> <arend.vanspriel@broadcom.com> wrote:
>>>>
>>>> Yup. Windows firmware talks NDIS. If you run 'strings 4345r6rtecdc.bin |
>>>> tail -1' you can see the firmware build target and it likely has 'ndis'
>>>> in
>>>> it.
>>
>>
>> Hi Daniel,
>>
>> Bit late response. Sorry.
>>
>>>
>>> 43455c0-roml/sdio-ag-ndis-vista-pktfilter-d0c-pno-aoe-p2p-dhdoid-ndoe-gtkoe-mfp-proptxstatus-dmatxrc-keepalive-ap-ampduretry-pclose-txbf
>>>
>>> Yes, ndis. So no easy way to run the same firmware on the 2 OSes.
>>
>>
>> Indeed. I could try building nearly same firmware target. Can you provide
>> the firmware version as well.
>>
>> Now reading over your orignal email again:
>>
>>> If I place both antenna terminals inside the Linux MiniPC case, the
>>> Linux pings are bad but the Windows pings are fine.
>>>
>>> If I place both antenna terminals inside the Windows MiniPC case, it
>>> is the same: Linux pings are bad, but the Windows pings are fine.
>>>
>>> And when the Linux antenna is placed outside of both cases, the Linux
>>> pings are fine. I've repeated these tests a handful of times in quick
>>> succession to make sure that I'm not going crazy and that this is not
>>> a case of the problem intermittency causing misleading results. These
>>> findings appear very solid.
>>
>> So it picks up something in the PC. Some sources of interference that I have
>> seen before are USB3 and HDMI. Maybe try to shield those if present and see
>> if that helps. The nvram contains sensitivity parameters, but as you stated
>> you are using the same nvram for windows and linux for now we can rule it
>> out for debugging the issue.
>>
>
> Hi Daniel,
>
> I'll jump in here too...
>
> Did you check the Bluetooth?  I don't know if this chip has it or if
> it's an independent chip on this board, but if Linux is leaving it
> powered up but not properly configured you could have issues. And in
> some designs, the BT and WiFi will share a single antenna. Note that
> I'm not saying you've configured BT to run, I'm actually suggesting
> that the pin that enables it is on, but you might not be loading the
> BT drivers and firmware and so the thing is just in a wonky
> uninitialized state. Or you do have it enabled and should try turning
> it off.  Either way.
>
> And WiFi/BT coex has always been a bit of a problem (speaking
> generally, I don't know the status with this particular chip) in
> Linux. I see WiFi and BT interfering with each other frequently in my
> testing setups with my dev boards. Often I can magically make problems
> go away by simply pulling the enable line high (which is "off").

Thanks, Steve

Disabling BT was indeed suggested, but indeed pulling BT_REG_ON high 
will ensure there is nothing active on BT side. In BT the firmware is 
generally speaking on-chip with possibility to download firmware patch 
to the device. However, if no driver does hci initialization I would 
expect BT to be passive/silent, but I guess your magic proves otherwise ;-)

Regards,
Arend