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Date: Sun, 11 Oct 2020 11:09:44 +0200
From: Willy Tarreau <w@....eu>
To: Nicolas Ferre <nicolas.ferre@...rochip.com>,
Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc: netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Willy Tarreau <w@....eu>,
Daniel Palmer <daniel@...f.com>
Subject: [PATCH net-next 3/3] 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 <nicolas.ferre@...rochip.com>
Cc: Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc: Daniel Palmer <daniel@...f.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
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 e87db95fb0f6..f8133003981f 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -1208,6 +1208,8 @@ 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 ca6e5456906a..6ff8e4b0b95d 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -3909,6 +3909,7 @@ 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));
@@ -3925,6 +3926,7 @@ 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));
@@ -3994,11 +3996,10 @@ 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;
@@ -4012,6 +4013,15 @@ 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 */
@@ -4077,6 +4087,8 @@ 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.
@@ -4088,21 +4100,39 @@ 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 */
--
2.28.0
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