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net/ena: fix unneeded doorbell submission

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Avoid submitting doorbell when:
* no packets have been submitted to TX
* no free resources have been submitted while RX

Sending doorbell without actual work to be performed by device
violates ENA specification and can lead to unpredictable behavior.

Fixes: 1173fca25af9 ("ena: add polling-mode driver")

Signed-off-by: Alexander Matushevsky <matua@amazon.com>
Signed-off-by: Jan Medala <jan@semihalf.com>
This commit is contained in:
Jan Medala 2016-07-08 13:11:30 +02:00 committed by Bruce Richardson
parent 620b173ae0
commit 5e02e19eb1
1 changed files with 22 additions and 11 deletions
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33
drivers/net/ena/ena_ethdev.c
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@ -1155,10 +1155,14 @@ static int ena_populate_rx_queue(struct ena_ring *rxq, unsigned int count)
next_to_use = ENA_RX_RING_IDX_NEXT(next_to_use, ring_size); next_to_use = ENA_RX_RING_IDX_NEXT(next_to_use, ring_size);
} }
rte_wmb(); /* When we submitted free recources to device... */
rxq->next_to_use = next_to_use; if (i > 0) {
/* let HW know that it can fill buffers with data */ /* ...let HW know that it can fill buffers with data */
ena_com_write_sq_doorbell(rxq->ena_com_io_sq); rte_wmb();
ena_com_write_sq_doorbell(rxq->ena_com_io_sq);
rxq->next_to_use = next_to_use;
}
return i; return i;
} }
@ -1564,7 +1568,7 @@ static uint16_t eth_ena_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
struct ena_tx_buffer *tx_info; struct ena_tx_buffer *tx_info;
struct ena_com_buf *ebuf; struct ena_com_buf *ebuf;
uint16_t rc, req_id, total_tx_descs = 0; uint16_t rc, req_id, total_tx_descs = 0;
int sent_idx = 0; uint16_t sent_idx = 0;
int nb_hw_desc; int nb_hw_desc;
/* Check adapter state */ /* Check adapter state */
@ -1643,9 +1647,14 @@ static uint16_t eth_ena_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
next_to_use = ENA_TX_RING_IDX_NEXT(next_to_use, ring_size); next_to_use = ENA_TX_RING_IDX_NEXT(next_to_use, ring_size);
} }
/* Let HW do it's best :-) */ /* If there are ready packets to be xmitted... */
rte_wmb(); if (sent_idx > 0) {
ena_com_write_sq_doorbell(tx_ring->ena_com_io_sq); /* ...let HW do its best :-) */
rte_wmb();
ena_com_write_sq_doorbell(tx_ring->ena_com_io_sq);
tx_ring->next_to_use = next_to_use;
}
/* Clear complete packets */ /* Clear complete packets */
while (ena_com_tx_comp_req_id_get(tx_ring->ena_com_io_cq, &req_id) >= 0) { while (ena_com_tx_comp_req_id_get(tx_ring->ena_com_io_cq, &req_id) >= 0) {
@ -1668,9 +1677,11 @@ static uint16_t eth_ena_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
break; break;
} }
/* acknowledge completion of sent packets */ if (total_tx_descs > 0) {
ena_com_comp_ack(tx_ring->ena_com_io_sq, total_tx_descs); /* acknowledge completion of sent packets */
tx_ring->next_to_use = next_to_use; ena_com_comp_ack(tx_ring->ena_com_io_sq, total_tx_descs);
}
return sent_idx; return sent_idx;
} }