From 0a4e9ce17ba77847e5a9f87eed3c0ba46e3f82eb Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Sun, 11 Oct 2020 11:09:44 +0200 Subject: [PATCH] macb: support the two tx descriptors on at91rm9200 The at91rm9200 variant used by a few chips including the MSC313 supports two Tx descriptors (one frame being serialized and another one queued). However the driver only implemented a single one, which adds a dead time after each transfer to receive and process the interrupt and wake the queue up, preventing from reaching line rate. This patch implements a very basic 2-deep queue to address this limitation. The tests run on a Breadbee board equipped with an MSC313E show that at 1 GHz, HTTP traffic on medium-sized objects (45kB) was limited to exactly 50 Mbps before this patch, and jumped to 76 Mbps with this patch. And tests on a single TCP stream with an MTU of 576 jump from 10kpps to 15kpps. With 1500 byte packets it's now possible to reach line rate versus 75 Mbps before. Cc: Nicolas Ferre Cc: Claudiu Beznea Cc: Daniel Palmer Signed-off-by: Willy Tarreau Link: https://lore.kernel.org/r/20201011090944.10607-4-w@1wt.eu Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/cadence/macb.h | 2 ++ drivers/net/ethernet/cadence/macb_main.c | 46 +++++++++++++++++++----- 2 files changed, 40 insertions(+), 8 deletions(-) diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h index 4c4672ff66a3..5de47f6fde5a 100644 --- a/drivers/net/ethernet/cadence/macb.h +++ b/drivers/net/ethernet/cadence/macb.h @@ -1209,6 +1209,8 @@ struct macb { /* AT91RM9200 transmit queue (1 on wire + 1 queued) */ struct macb_tx_skb rm9200_txq[2]; + unsigned int rm9200_tx_tail; + unsigned int rm9200_tx_len; unsigned int max_tx_length; u64 ethtool_stats[GEM_STATS_LEN + QUEUE_STATS_LEN * MACB_MAX_QUEUES]; diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index 35d2f7f42e0b..883e47c5b1a7 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -3908,6 +3908,7 @@ static int at91ether_start(struct macb *lp) MACB_BIT(ISR_TUND) | MACB_BIT(ISR_RLE) | MACB_BIT(TCOMP) | + MACB_BIT(RM9200_TBRE) | MACB_BIT(ISR_ROVR) | MACB_BIT(HRESP)); @@ -3924,6 +3925,7 @@ static void at91ether_stop(struct macb *lp) MACB_BIT(ISR_TUND) | MACB_BIT(ISR_RLE) | MACB_BIT(TCOMP) | + MACB_BIT(RM9200_TBRE) | MACB_BIT(ISR_ROVR) | MACB_BIT(HRESP)); @@ -3993,11 +3995,10 @@ static netdev_tx_t at91ether_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct macb *lp = netdev_priv(dev); + unsigned long flags; - if (macb_readl(lp, TSR) & MACB_BIT(RM9200_BNQ)) { - int desc = 0; - - netif_stop_queue(dev); + if (lp->rm9200_tx_len < 2) { + int desc = lp->rm9200_tx_tail; /* Store packet information (to free when Tx completed) */ lp->rm9200_txq[desc].skb = skb; @@ -4011,6 +4012,15 @@ static netdev_tx_t at91ether_start_xmit(struct sk_buff *skb, return NETDEV_TX_OK; } + spin_lock_irqsave(&lp->lock, flags); + + lp->rm9200_tx_tail = (desc + 1) & 1; + lp->rm9200_tx_len++; + if (lp->rm9200_tx_len > 1) + netif_stop_queue(dev); + + spin_unlock_irqrestore(&lp->lock, flags); + /* Set address of the data in the Transmit Address register */ macb_writel(lp, TAR, lp->rm9200_txq[desc].mapping); /* Set length of the packet in the Transmit Control register */ @@ -4076,6 +4086,8 @@ static irqreturn_t at91ether_interrupt(int irq, void *dev_id) struct macb *lp = netdev_priv(dev); u32 intstatus, ctl; unsigned int desc; + unsigned int qlen; + u32 tsr; /* MAC Interrupt Status register indicates what interrupts are pending. * It is automatically cleared once read. @@ -4087,21 +4099,39 @@ static irqreturn_t at91ether_interrupt(int irq, void *dev_id) at91ether_rx(dev); /* Transmit complete */ - if (intstatus & MACB_BIT(TCOMP)) { + if (intstatus & (MACB_BIT(TCOMP) | MACB_BIT(RM9200_TBRE))) { /* The TCOM bit is set even if the transmission failed */ if (intstatus & (MACB_BIT(ISR_TUND) | MACB_BIT(ISR_RLE))) dev->stats.tx_errors++; - desc = 0; - if (lp->rm9200_txq[desc].skb) { + spin_lock(&lp->lock); + + tsr = macb_readl(lp, TSR); + + /* we have three possibilities here: + * - all pending packets transmitted (TGO, implies BNQ) + * - only first packet transmitted (!TGO && BNQ) + * - two frames pending (!TGO && !BNQ) + * Note that TGO ("transmit go") is called "IDLE" on RM9200. + */ + qlen = (tsr & MACB_BIT(TGO)) ? 0 : + (tsr & MACB_BIT(RM9200_BNQ)) ? 1 : 2; + + while (lp->rm9200_tx_len > qlen) { + desc = (lp->rm9200_tx_tail - lp->rm9200_tx_len) & 1; dev_consume_skb_irq(lp->rm9200_txq[desc].skb); lp->rm9200_txq[desc].skb = NULL; dma_unmap_single(&lp->pdev->dev, lp->rm9200_txq[desc].mapping, lp->rm9200_txq[desc].size, DMA_TO_DEVICE); dev->stats.tx_packets++; dev->stats.tx_bytes += lp->rm9200_txq[desc].size; + lp->rm9200_tx_len--; } - netif_wake_queue(dev); + + if (lp->rm9200_tx_len < 2 && netif_queue_stopped(dev)) + netif_wake_queue(dev); + + spin_unlock(&lp->lock); } /* Work-around for EMAC Errata section 41.3.1 */