Ethernet LDD potential bug

PeterFromSweden — Thu, 08 May 2014 12:53:50 GMT

I am using CodeWarrior 10.6 and Processor Expert to generate Ethernet LDD. The code supplied runs on TWR-K60N512 and in just a few seconds reproduce my problem.

Problem is that I get one more OnFrameTransmitted than actual SendFrame's. When this occurrs it is always when OnFrameTransmitted interrupts an ongoing SendFrame. From a user perspective it is easy to say that I don't want more completed frame receipts than what I have scheduled for sending, but finding logical explanation to it is harder.

Please have a try on attached project and se for yourself! More info in main.c on steps to reproduce problem.

Regards

/Peter

Original Attachment has been moved to: EthernetPE.zip

Re: Ethernet LDD potential bug

PeterFromSweden — Fri, 09 May 2014 05:56:54 GMT

After investigation of this problem, I think I found the root cause of problem.

SendFrame adds to TxQueue in two steps. First without TX_READY flag and then in next step TX_READY flag is added.

The TX_READY flag is reset when ethernet peripheral has sent it.

InterruptTxFrame checks that TX_READY is reset to determine if OnFrameTransmit should take place.

Now, when interrupt occurrs between step 1 and 2 of SendFrame above, the frame is wrongly interpreted as already sent since the bit TX_READY is not yet set.

One solution is:

1) Add another flag, ETH1_TX_TO1, or-ed to TX_READY in step 2.

LDD_QUEUE_GET_TAIL_OFFSET_ITEM(DeviceDataPrv->TxQueue, BufferDescCount - Index).Flags |= ETH1_TX_READY; /* Enable buffer transmission */

LDD_QUEUE_GET_TAIL_OFFSET_ITEM(DeviceDataPrv->TxQueue, BufferDescCount - Index).Flags |=

ETH1_TX_READY | /* Enable buffer transmission */

ETH1_TX_TO1; /* Indicate that it has been enabled */

2) Add check for TX_TO1 in RemoveTxFrame

!(LDD_QUEUE_GET_HEAD_OFFSET_ITEM(DeviceDataPrv->TxQueue, BufferOffset).Flags & ETH1_TX_READY)) {

!(LDD_QUEUE_GET_HEAD_OFFSET_ITEM(DeviceDataPrv->TxQueue, BufferOffset).Flags & ETH1_TX_READY) &&

(LDD_QUEUE_GET_HEAD_OFFSET_ITEM(DeviceDataPrv->TxQueue, BufferOffset).Flags & ETH1_TX_TO1)) {

Hope this helps!

Regards

/Peter

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