ftgmac100: Cleanup tx queue handling
We have a private lock which isn't terribly useful, and we maintain a "tx_pending" counter for information that's already available via a trivial arithmetic operation. Then we unconditionaly wake the queue even when not stopped. Finally our code in tx isn't really safe vs. a concurrent reclaim. The aspeed chips aren't SMP today but I prefer the code being right and future proof. So rip that out and replace it with more "standard" queue handling, currently with a threshold of 1 queue element, which will be increased when we implement fragmented sends. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Benjamin Herrenschmidt
David S. Miller
Родитель
83617317d2
Коммит
6ad3d7edcb
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@ -46,6 +46,9 @@
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#define MAX_PKT_SIZE 1536
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#define RX_BUF_SIZE MAX_PKT_SIZE /* must be smaller than 0x3fff */
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/* Min number of tx ring entries before stopping queue */
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#define TX_THRESHOLD (1)
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struct ftgmac100_descs {
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struct ftgmac100_rxdes rxdes[RX_QUEUE_ENTRIES];
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struct ftgmac100_txdes txdes[TX_QUEUE_ENTRIES];
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@ -68,9 +71,7 @@ struct ftgmac100 {
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struct sk_buff *tx_skbs[TX_QUEUE_ENTRIES];
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unsigned int tx_clean_pointer;
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unsigned int tx_pointer;
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unsigned int tx_pending;
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u32 txdes0_edotr_mask;
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spinlock_t tx_lock;
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/* Scratch page to use when rx skb alloc fails */
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void *rx_scratch;
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@ -165,7 +166,6 @@ static int ftgmac100_reset_and_config_mac(struct ftgmac100 *priv)
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priv->rx_pointer = 0;
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priv->tx_clean_pointer = 0;
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priv->tx_pointer = 0;
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priv->tx_pending = 0;
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/* The doc says reset twice with 10us interval */
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if (ftgmac100_reset_mac(priv, maccr))
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@ -551,6 +551,23 @@ static int ftgmac100_next_tx_pointer(int pointer)
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return (pointer + 1) & (TX_QUEUE_ENTRIES - 1);
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}
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static u32 ftgmac100_tx_buf_avail(struct ftgmac100 *priv)
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{
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/* Returns the number of available slots in the TX queue
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*
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* This always leaves one free slot so we don't have to
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* worry about empty vs. full, and this simplifies the
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* test for ftgmac100_tx_buf_cleanable() below
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*/
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return (priv->tx_clean_pointer - priv->tx_pointer - 1) &
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(TX_QUEUE_ENTRIES - 1);
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}
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static bool ftgmac100_tx_buf_cleanable(struct ftgmac100 *priv)
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{
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return priv->tx_pointer != priv->tx_clean_pointer;
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}
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static bool ftgmac100_tx_complete_packet(struct ftgmac100 *priv)
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{
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struct net_device *netdev = priv->netdev;
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@ -559,9 +576,6 @@ static bool ftgmac100_tx_complete_packet(struct ftgmac100 *priv)
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struct sk_buff *skb;
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dma_addr_t map;
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if (priv->tx_pending == 0)
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return false;
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pointer = priv->tx_clean_pointer;
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txdes = &priv->descs->txdes[pointer];
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@ -583,18 +597,31 @@ static bool ftgmac100_tx_complete_packet(struct ftgmac100 *priv)
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priv->tx_clean_pointer = ftgmac100_next_tx_pointer(pointer);
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spin_lock(&priv->tx_lock);
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priv->tx_pending--;
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spin_unlock(&priv->tx_lock);
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netif_wake_queue(netdev);
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return true;
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}
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static void ftgmac100_tx_complete(struct ftgmac100 *priv)
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{
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while (ftgmac100_tx_complete_packet(priv))
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struct net_device *netdev = priv->netdev;
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/* Process all completed packets */
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while (ftgmac100_tx_buf_cleanable(priv) &&
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ftgmac100_tx_complete_packet(priv))
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;
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/* Restart queue if needed */
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smp_mb();
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if (unlikely(netif_queue_stopped(netdev) &&
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ftgmac100_tx_buf_avail(priv) >= TX_THRESHOLD)) {
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struct netdev_queue *txq;
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txq = netdev_get_tx_queue(netdev, 0);
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__netif_tx_lock(txq, smp_processor_id());
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if (netif_queue_stopped(netdev) &&
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ftgmac100_tx_buf_avail(priv) >= TX_THRESHOLD)
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netif_wake_queue(netdev);
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__netif_tx_unlock(txq);
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}
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}
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static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
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@ -652,17 +679,22 @@ static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
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}
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}
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ftgmac100_txdes_set_dma_own(txdes);
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/* Update next TX pointer */
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priv->tx_pointer = ftgmac100_next_tx_pointer(pointer);
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spin_lock(&priv->tx_lock);
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priv->tx_pending++;
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if (priv->tx_pending == TX_QUEUE_ENTRIES)
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/* If there isn't enough room for all the fragments of a new packet
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* in the TX ring, stop the queue. The sequence below is race free
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* vs. a concurrent restart in ftgmac100_poll()
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*/
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if (unlikely(ftgmac100_tx_buf_avail(priv) < TX_THRESHOLD)) {
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netif_stop_queue(netdev);
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/* start transmit */
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ftgmac100_txdes_set_dma_own(txdes);
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spin_unlock(&priv->tx_lock);
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/* Order the queue stop with the test below */
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smp_mb();
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if (ftgmac100_tx_buf_avail(priv) >= TX_THRESHOLD)
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netif_wake_queue(netdev);
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}
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ftgmac100_txdma_normal_prio_start_polling(priv);
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@ -980,17 +1012,17 @@ static bool ftgmac100_check_rx(struct ftgmac100 *priv)
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static int ftgmac100_poll(struct napi_struct *napi, int budget)
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{
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struct ftgmac100 *priv = container_of(napi, struct ftgmac100, napi);
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bool more, completed = true;
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int rx = 0;
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int work_done = 0;
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bool more;
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ftgmac100_tx_complete(priv);
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/* Handle TX completions */
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if (ftgmac100_tx_buf_cleanable(priv))
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ftgmac100_tx_complete(priv);
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/* Handle RX packets */
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do {
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more = ftgmac100_rx_packet(priv, &rx);
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} while (more && rx < budget);
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if (more && rx == budget)
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completed = false;
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more = ftgmac100_rx_packet(priv, &work_done);
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} while (more && work_done < budget);
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/* The interrupt is telling us to kick the MAC back to life
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@ -1004,11 +1036,13 @@ static int ftgmac100_poll(struct napi_struct *napi, int budget)
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priv->base + FTGMAC100_OFFSET_IER);
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}
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/* Keep NAPI going if we have still packets to reclaim */
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if (priv->tx_pending)
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return budget;
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/* As long as we are waiting for transmit packets to be
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* completed we keep NAPI going
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*/
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if (ftgmac100_tx_buf_cleanable(priv))
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work_done = budget;
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if (completed) {
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if (work_done < budget) {
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/* We are about to re-enable all interrupts. However
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* the HW has been latching RX/TX packet interrupts while
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* they were masked. So we clear them first, then we need
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@ -1016,7 +1050,8 @@ static int ftgmac100_poll(struct napi_struct *napi, int budget)
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*/
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iowrite32(FTGMAC100_INT_RXTX,
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priv->base + FTGMAC100_OFFSET_ISR);
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if (ftgmac100_check_rx(priv) || priv->tx_pending)
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if (ftgmac100_check_rx(priv) ||
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ftgmac100_tx_buf_cleanable(priv))
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return budget;
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/* deschedule NAPI */
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@ -1027,7 +1062,7 @@ static int ftgmac100_poll(struct napi_struct *napi, int budget)
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priv->base + FTGMAC100_OFFSET_IER);
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}
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return rx;
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return work_done;
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}
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static int ftgmac100_init_all(struct ftgmac100 *priv, bool ignore_alloc_err)
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@ -1355,8 +1390,6 @@ static int ftgmac100_probe(struct platform_device *pdev)
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priv->dev = &pdev->dev;
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INIT_WORK(&priv->reset_task, ftgmac100_reset_task);
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spin_lock_init(&priv->tx_lock);
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/* map io memory */
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priv->res = request_mem_region(res->start, resource_size(res),
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dev_name(&pdev->dev));
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