[yocto] [meta-raspberrypi] PL2303 instability on RPi 3 but not on RPi 2

[Martin Bergek]

Thanks Andrei,

I have done some more testing and I have found that - with everything else being the same - I can only see the issue on kernel 4.4. On kernel 4.1 it is stable.

As an alternative workaround I have noticed that disabling USB 2.0 by booting with dwc_otg.speed=1 makes the system stable on any kernel version - albeit of course with much lower USB speeds.

For my particular application either of these alternatives work but I would rather use the latest kernel and at full USB speed.

I have tried changing the core frequency (i.e. core_freq=250) but that didn’t make any difference. The change seems to be mostly related to the serial ports on the RPi which is not the same as the problem I am experiencing. My problem is that the USB ports on the RPi stop working.

/Martin


> On 08 Jul 2016, at 15:42, Andrei Gherzan <andrei at gherzan.ro> wrote:
> 
> On Mon, Jun 13, 2016 at 11:24:08PM +0200, Martin Bergek wrote:
>> Hi,
>> 
>> I am testing an image on a system including a PL2303 (USB to serial bridge) and have noticed an issue on the Raspberry Pi 3. The system will run fine for an hour or two but then the kernel logs the following error:
>> 
>> 	pl2303 ttyUSB0: usb_serial_generic_read_bulk_callback - urb stopped: -32
>> 
>> After this there is no more data coming from the USB device and I have to either reboot or disconnect/connect the USB device - neither of which is acceptable in my application.
>> 
>> This is on kernel 4.4.9 and it happens only on the Raspberry Pi 3. On Raspberry Pi 2 the exact same firmware runs flawlessly.
>> 
>> Has anyone else come across this or have some suggestions on how to solve it? Or how to pinpoint the cause?
>> 
>> Thanks,
>> Martin Bergek
>> 
> 
> I'm usign exactly the same chipset and never saw this problem before.
> There might be something related to
> https://github.com/raspberrypi/firmware/issues/553 which you can test
> with a core_freq=250
> 
> As well it might be connected to the USB power supply if you use the 5V pin
> from PL2303 to power up your board. I do and I experience no issue but
> it might be something there.
> 
> --
> Andrei Gherzan