Azurewave CM276(88W8997) and Cinterion PHS8P conflict

[j_mazura]

Hello,

we are using the 88W8997 chip and gsm modem PHS8P(both on USB) in our device. We noticed, when we use gsm modem(send some AT command), wifi chip will stop working. With lots of debuging(looking into EHCI) we found out, when at least one URB on INT EP5 IN of modem's ttyUSB line is submited, all(6) 88W8997's OUT BULK URBs are stopped in processing. They are still in some structures in ehci, URB "complete function" is not called...

We tested kernel 4.1.52 on IMX53, 4.14, 4,19, 5.4 on IMX6, 5.7.9 on PC always with same result. For wifi we use driver from kernel(mwifiex) with Marvel's driver(mlan and mlinux) it was same. Modem is using driver option(usb_wwan). 

Has anyone seen similar conflict on USB?

Regards

Jan

[j_mazura]

Hello,

I have new knowledge. If I slow down wifi's usb to FS with FS hub, superior USB hub has to translate messages from HS to FS. It translates only messages with wifi's address, so wifi cannot "hear" USB modem's communication on endpoint 5 and everything is working. Unfortunately this workaround needs PCB redesign or wifi's firmware modification...

Regards

Jan

[jamesbone]

Please contact direclty AzureWave in order to have an update of the linux driver for the 88W8997,  if they have an issue they will report directly to NXP.

[j_mazura]

Hello,

I did it but is seems, the communication via AzurWave is not so effective as could be. We have discovered that our issue is caused by communication on endpoint 5. When another USB device(for example USB modem) makes communication with his driver on endpoint 5, firmware in 88W8997 will partly crash, stop receiving urbs on endpoint 2 and start sending NAKs, so driver mwifiex cannot send any data to 88W8997. I did dump of communication with USB analyzer, where we can see this NAKs. We was able reproduce this issue with rPi zero configured as mass-storage, modified to use endpoint 5, connected to USB hub next to wifi module... so does not matter on type of device, which is using endpoint 5 ... We are using driver mwifiex, with mlan&mlinux I got same results. I am almost sure, this cannot be solved in wifi driver but only in firmware of this module.

Regards

Jan