topic Re: ethernet transmit buffer full in Kinetis Software Development Kit

ethernet transmit buffer full

mrtumnus — Thu, 06 Oct 2016 21:00:28 GMT

I am developing a product using an MK64FN1M0VLL12 microcontroller and a two-port managed ethernet switch, SMSC's LAN9303i. I have encountered a problem in which the ethernet driver seems to lock up after a flood of packets (ICMP/ping, in this case). The symptom is that the transmit buffer ring appears to fill up, but gets in a state where it never gets cleaned up. Subsequent calls to ENET_DRV_SendData fail due to the buffer being full. I do not observe the Tx interrupt ever being triggered in this state (thus, ENET_DRV_CleanupTxBuffDescrip() is never called, which 'frees' up buffer descriptors).

The only options I can think of are:

Apply some band-aid by manually cleaning up the buffer descriptor ring (when? how?)
Increase the transmit buffer ring size. This also seems like a band-aid that doesn't address the root problem.
Reset the whole driver when this state occurs (last resort)

Re: ethernet transmit buffer full

manfredschnell — Fri, 07 Oct 2016 05:34:10 GMT

Hi Elliott,

I had a similar problem with K64 + KSDK2.0 and KSZ8863MLL switching ethernet phy. On a packet flood the buffer memory is filled up with incomming messages --> no memory for tx.

Please have a look at FRDM-K64F KSDK 1.3.0 tcp_echo demo bugs? and my last post according the priority of lwIPInterruptTask() an tcpip_thread().

You should to something like this in your system.

If you have further questions, don't hesitate to ask.

Best regards

Manfred

Re: ethernet transmit buffer full

mrtumnus — Fri, 07 Oct 2016 14:16:59 GMT

Manfred,

Thanks very much for the quick reply. I failed to mention that I am not using an RTOS, just a bare-metal application. However, you raise a good point that the Rx interrupt may be firing during the handling of an outgoing frame. I will check into disabling interrupt(s) during this time. Do you think this might be the same issue, but on a bare-metal app?

Regards,

Elliott

Re: ethernet transmit buffer full

manfredschnell — Mon, 10 Oct 2016 07:46:21 GMT

Hi Elliott,

the issue is the same, regardless of the underlaying system.

You have to take care for calling tcpip_thread() enough times in your bare-metal application.

I think it's not necessary to disable RX-IRQ. The RX driver will handle the case, when no buffer is free.

Instead I would process the already received packets.

Do you have enough memory buffers?

My application uses:

#define PBUF_POOL_SIZE 32

#define PBUF_POOL_BUFSIZE 256U

Did you rework the "ethernetif_Input()"? The original KSDK2.0 version leads to strange errors, because of an error when receiving into chained buffers. --> memory is overwritten...

Have a look on my "ethernetif_Input()" in https://community.nxp.com/thread/395104‌

Best regards

Manfred