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ftgmac100: Cleanup tx queue handling

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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 2017-04-10 11:15:21 +10:00 committed by David S. Miller
parent 83617317d2
commit 6ad3d7edcb
1 changed files with 68 additions and 35 deletions
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103
drivers/net/ethernet/faraday/ftgmac100.c
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@ -46,6 +46,9 @@
#define MAX_PKT_SIZE 1536
#define RX_BUF_SIZE MAX_PKT_SIZE /* must be smaller than 0x3fff */
/* Min number of tx ring entries before stopping queue */
#define TX_THRESHOLD (1)
struct ftgmac100_descs {
struct ftgmac100_rxdes rxdes[RX_QUEUE_ENTRIES];
struct ftgmac100_txdes txdes[TX_QUEUE_ENTRIES];
@ -68,9 +71,7 @@ struct ftgmac100 {
struct sk_buff *tx_skbs[TX_QUEUE_ENTRIES];
unsigned int tx_clean_pointer;
unsigned int tx_pointer;
unsigned int tx_pending;
u32 txdes0_edotr_mask;
spinlock_t tx_lock;
/* Scratch page to use when rx skb alloc fails */
void *rx_scratch;
@ -165,7 +166,6 @@ static int ftgmac100_reset_and_config_mac(struct ftgmac100 *priv)
priv->rx_pointer = 0;
priv->tx_clean_pointer = 0;
priv->tx_pointer = 0;
priv->tx_pending = 0;
/* The doc says reset twice with 10us interval */
if (ftgmac100_reset_mac(priv, maccr))
@ -551,6 +551,23 @@ static int ftgmac100_next_tx_pointer(int pointer)
return (pointer + 1) & (TX_QUEUE_ENTRIES - 1);
}
static u32 ftgmac100_tx_buf_avail(struct ftgmac100 *priv)
{
/* Returns the number of available slots in the TX queue
*
* This always leaves one free slot so we don't have to
* worry about empty vs. full, and this simplifies the
* test for ftgmac100_tx_buf_cleanable() below
*/
return (priv->tx_clean_pointer - priv->tx_pointer - 1) &
(TX_QUEUE_ENTRIES - 1);
}
static bool ftgmac100_tx_buf_cleanable(struct ftgmac100 *priv)
{
return priv->tx_pointer != priv->tx_clean_pointer;
}
static bool ftgmac100_tx_complete_packet(struct ftgmac100 *priv)
{
struct net_device *netdev = priv->netdev;
@ -559,9 +576,6 @@ static bool ftgmac100_tx_complete_packet(struct ftgmac100 *priv)
struct sk_buff *skb;
dma_addr_t map;
if (priv->tx_pending == 0)
return false;
pointer = priv->tx_clean_pointer;
txdes = &priv->descs->txdes[pointer];
@ -583,18 +597,31 @@ static bool ftgmac100_tx_complete_packet(struct ftgmac100 *priv)
priv->tx_clean_pointer = ftgmac100_next_tx_pointer(pointer);
spin_lock(&priv->tx_lock);
priv->tx_pending--;
spin_unlock(&priv->tx_lock);
netif_wake_queue(netdev);
return true;
}
static void ftgmac100_tx_complete(struct ftgmac100 *priv)
{
while (ftgmac100_tx_complete_packet(priv))
struct net_device *netdev = priv->netdev;
/* Process all completed packets */
while (ftgmac100_tx_buf_cleanable(priv) &&
ftgmac100_tx_complete_packet(priv))
;
/* Restart queue if needed */
smp_mb();
if (unlikely(netif_queue_stopped(netdev) &&
ftgmac100_tx_buf_avail(priv) >= TX_THRESHOLD)) {
struct netdev_queue *txq;
txq = netdev_get_tx_queue(netdev, 0);
__netif_tx_lock(txq, smp_processor_id());
if (netif_queue_stopped(netdev) &&
ftgmac100_tx_buf_avail(priv) >= TX_THRESHOLD)
netif_wake_queue(netdev);
__netif_tx_unlock(txq);
}
}
static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
@ -652,17 +679,22 @@ static int ftgmac100_hard_start_xmit(struct sk_buff *skb,
}
}
ftgmac100_txdes_set_dma_own(txdes);
/* Update next TX pointer */
priv->tx_pointer = ftgmac100_next_tx_pointer(pointer);
spin_lock(&priv->tx_lock);
priv->tx_pending++;
if (priv->tx_pending == TX_QUEUE_ENTRIES)
/* If there isn't enough room for all the fragments of a new packet
* in the TX ring, stop the queue. The sequence below is race free
* vs. a concurrent restart in ftgmac100_poll()
*/
if (unlikely(ftgmac100_tx_buf_avail(priv) < TX_THRESHOLD)) {
netif_stop_queue(netdev);
/* start transmit */
ftgmac100_txdes_set_dma_own(txdes);
spin_unlock(&priv->tx_lock);
/* Order the queue stop with the test below */
smp_mb();
if (ftgmac100_tx_buf_avail(priv) >= TX_THRESHOLD)
netif_wake_queue(netdev);
}
ftgmac100_txdma_normal_prio_start_polling(priv);
@ -980,17 +1012,17 @@ static bool ftgmac100_check_rx(struct ftgmac100 *priv)
static int ftgmac100_poll(struct napi_struct *napi, int budget)
{
struct ftgmac100 *priv = container_of(napi, struct ftgmac100, napi);
bool more, completed = true;
int rx = 0;
int work_done = 0;
bool more;
ftgmac100_tx_complete(priv);
/* Handle TX completions */
if (ftgmac100_tx_buf_cleanable(priv))
ftgmac100_tx_complete(priv);
/* Handle RX packets */
do {
more = ftgmac100_rx_packet(priv, &rx);
} while (more && rx < budget);
if (more && rx == budget)
completed = false;
more = ftgmac100_rx_packet(priv, &work_done);
} while (more && work_done < budget);
/* The interrupt is telling us to kick the MAC back to life
@ -1004,11 +1036,13 @@ static int ftgmac100_poll(struct napi_struct *napi, int budget)
priv->base + FTGMAC100_OFFSET_IER);
}
/* Keep NAPI going if we have still packets to reclaim */
if (priv->tx_pending)
return budget;
/* As long as we are waiting for transmit packets to be
* completed we keep NAPI going
*/
if (ftgmac100_tx_buf_cleanable(priv))
work_done = budget;
if (completed) {
if (work_done < budget) {
/* We are about to re-enable all interrupts. However
* the HW has been latching RX/TX packet interrupts while
* they were masked. So we clear them first, then we need
@ -1016,7 +1050,8 @@ static int ftgmac100_poll(struct napi_struct *napi, int budget)
*/
iowrite32(FTGMAC100_INT_RXTX,
priv->base + FTGMAC100_OFFSET_ISR);
if (ftgmac100_check_rx(priv) || priv->tx_pending)
if (ftgmac100_check_rx(priv) ||
ftgmac100_tx_buf_cleanable(priv))
return budget;
/* deschedule NAPI */
@ -1027,7 +1062,7 @@ static int ftgmac100_poll(struct napi_struct *napi, int budget)
priv->base + FTGMAC100_OFFSET_IER);
}
return rx;
return work_done;
}
static int ftgmac100_init_all(struct ftgmac100 *priv, bool ignore_alloc_err)
@ -1355,8 +1390,6 @@ static int ftgmac100_probe(struct platform_device *pdev)
priv->dev = &pdev->dev;
INIT_WORK(&priv->reset_task, ftgmac100_reset_task);
spin_lock_init(&priv->tx_lock);
/* map io memory */
priv->res = request_mem_region(res->start, resource_size(res),
dev_name(&pdev->dev));