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I suppose this could simply be >> hiding any subsequent errors, so once this is fixed we might see other >> similar issues. > > Well, having a quick look at this, the first thing which stands out is: > > In stmmac_tx_clean(), we have: > > if (likely(tx_q->tx_skbuff_dma[entry].buf && > tx_q->tx_skbuff_dma[entry].buf_type != STMMAC_TXBUF_T > _XDP_TX)) { > if (tx_q->tx_skbuff_dma[entry].map_as_page) > dma_unmap_page(priv->device, > tx_q->tx_skbuff_dma[entry].buf, > tx_q->tx_skbuff_dma[entry].len, > DMA_TO_DEVICE); > else > dma_unmap_single(priv->device, > tx_q->tx_skbuff_dma[entry].buf, > tx_q->tx_skbuff_dma[entry].len, > DMA_TO_DEVICE); > tx_q->tx_skbuff_dma[entry].buf = 0; > tx_q->tx_skbuff_dma[entry].len = 0; > tx_q->tx_skbuff_dma[entry].map_as_page = false; > } > > So, tx_skbuff_dma[entry].buf is expected to point appropriately to the > DMA region. > > Now if we look at stmmac_tso_xmit(): > > des = dma_map_single(priv->device, skb->data, skb_headlen(skb), > DMA_TO_DEVICE); > if (dma_mapping_error(priv->device, des)) > goto dma_map_err; > > if (priv->dma_cap.addr64 <= 32) { > ... > } else { > ... > des += proto_hdr_len; > ... > } > > tx_q->tx_skbuff_dma[tx_q->cur_tx].buf = des; > tx_q->tx_skbuff_dma[tx_q->cur_tx].len = skb_headlen(skb); > tx_q->tx_skbuff_dma[tx_q->cur_tx].map_as_page = false; > tx_q->tx_skbuff_dma[tx_q->cur_tx].buf_type = STMMAC_TXBUF_T_SKB; > > This will result in stmmac_tx_clean() calling dma_unmap_single() using > "des" and "skb_headlen(skb)" as the buffer start and length. > > One of the requirements of the DMA mapping API is that the DMA handle > returned by the map operation will be passed into the unmap function. > Not something that was offset. The length will also be the same. > > We can clearly see above that there is a case where the DMA handle has > been offset by proto_hdr_len, and when this is so, the value that is > passed into the unmap operation no longer matches this requirement. > > So, a question to the reporter - what is the value of > priv->dma_cap.addr64 in your failing case? You should see the value > in the "Using %d/%d bits DMA host/device width" kernel message. It is ... dwc-eth-dwmac 2490000.ethernet: Using 40/40 bits DMA host/device width Thanks Jon -- nvpublic