[dpdk-dev] [RFC 7/9] net/igb: add handler for tx queue descriptor count

[Olivier Matz]

Like for TX, use a binary search algorithm to get the number of used Tx
descriptors.

PR=52423
Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
Acked-by: Ivan Boule <ivan.boule at 6wind.com>
---
 drivers/net/e1000/e1000_ethdev.h |  5 +++-
 drivers/net/e1000/igb_ethdev.c   |  1 +
 drivers/net/e1000/igb_rxtx.c     | 51 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/drivers/net/e1000/e1000_ethdev.h b/drivers/net/e1000/e1000_ethdev.h
index 6c25c8d..ad9ddaf 100644
--- a/drivers/net/e1000/e1000_ethdev.h
+++ b/drivers/net/e1000/e1000_ethdev.h
@@ -300,7 +300,10 @@ int eth_igb_rx_queue_setup(struct rte_eth_dev *dev, 
uint16_t rx_queue_id,
                struct rte_mempool *mb_pool);

 uint32_t eth_igb_rx_queue_count(struct rte_eth_dev *dev,
-               uint16_t rx_queue_id);
+                               uint16_t rx_queue_id);
+
+uint32_t eth_igb_tx_queue_count(struct rte_eth_dev *dev,
+                               uint16_t tx_queue_id);

 int eth_igb_rx_descriptor_done(void *rx_queue, uint16_t offset);

diff --git a/drivers/net/e1000/igb_ethdev.c b/drivers/net/e1000/igb_ethdev.c
index 08f2a68..a54d374 100644
--- a/drivers/net/e1000/igb_ethdev.c
+++ b/drivers/net/e1000/igb_ethdev.c
@@ -399,6 +399,7 @@ static const struct eth_dev_ops eth_igb_ops = {
        .rx_queue_intr_disable = eth_igb_rx_queue_intr_disable,
        .rx_queue_release     = eth_igb_rx_queue_release,
        .rx_queue_count       = eth_igb_rx_queue_count,
+       .tx_queue_count       = eth_igb_tx_queue_count,
        .rx_descriptor_done   = eth_igb_rx_descriptor_done,
        .tx_queue_setup       = eth_igb_tx_queue_setup,
        .tx_queue_release     = eth_igb_tx_queue_release,
diff --git a/drivers/net/e1000/igb_rxtx.c b/drivers/net/e1000/igb_rxtx.c
index 6b0111f..2ff2417 100644
--- a/drivers/net/e1000/igb_rxtx.c
+++ b/drivers/net/e1000/igb_rxtx.c
@@ -1554,6 +1554,57 @@ eth_igb_rx_queue_count(struct rte_eth_dev *dev, uint16_t 
rx_queue_id)
        return offset;
 }

+uint32_t
+eth_igb_tx_queue_count(struct rte_eth_dev *dev, uint16_t tx_queue_id)
+{
+       volatile uint32_t *status;
+       struct igb_tx_queue *txq;
+       int32_t offset, interval, idx, resolution;
+
+       txq = dev->data->tx_queues[tx_queue_id];
+
+       /* check if ring empty */
+       idx = txq->tx_tail - 1;
+       if (idx < 0)
+               idx += txq->nb_tx_desc;
+       status = &txq->tx_ring[idx].wb.status;
+       if (*status & rte_cpu_to_le_32(E1000_TXD_STAT_DD))
+               return 0;
+
+       /* check if ring full */
+       idx = txq->tx_tail + 1;
+       if (idx >= txq->nb_tx_desc)
+               idx -= txq->nb_tx_desc;
+       status = &txq->tx_ring[idx].wb.status;
+       if (!(*status & rte_cpu_to_le_32(E1000_TXD_STAT_DD)))
+               return txq->nb_tx_desc;
+
+       /* decrease the precision if ring is large */
+       if (txq->nb_tx_desc <= 256)
+               resolution = 4;
+       else
+               resolution = 16;
+
+       /* use a binary search */
+       interval = txq->nb_tx_desc >> 1;
+       offset = interval;
+
+       do {
+               interval >>= 1;
+               idx = txq->tx_tail + offset;
+               if (idx >= txq->nb_tx_desc)
+                       idx -= txq->nb_tx_desc;
+
+               status = &txq->tx_ring[idx].wb.status;
+               if (*status & rte_cpu_to_le_32(E1000_TXD_STAT_DD))
+                       offset += interval;
+               else
+                       offset -= interval;
+       } while (interval >= resolution);
+
+       return txq->nb_tx_desc - offset;
+}
+
 int
 eth_igb_rx_descriptor_done(void *rx_queue, uint16_t offset)
 {
-- 
2.8.1