Re: [PATCH net-next V2 04/16] net: fec: reduce interrupts

On Wed, Mar 2, 2016 at 10:12 AM, Troy Kisky
[off-list ref] wrote:

On 3/2/2016 8:13 AM, Fugang Duan wrote:

quoted

From: Troy Kisky <redacted> Sent: Thursday, February 25, 2016 8:37 AM

quoted

To: netdev@vger.kernel.org; davem@davemloft.net; b38611@freescale.com
Cc: fabio.estevam@freescale.com; l.stach@pengutronix.de; andrew@lunn.ch;
tremyfr@gmail.com; linux@arm.linux.org.uk; linux-arm-
kernel@lists.infradead.org; laci@boundarydevices.com; shawnguo@kernel.org;
johannes@sipsolutions.net; stillcompiling@gmail.com;
sergei.shtylyov@cogentembedded.com; arnd@arndb.de; Troy Kisky
[off-list ref]
Subject: [PATCH net-next V2 04/16] net: fec: reduce interrupts

By clearing the NAPI interrupts in the NAPI routine and not in the interrupt
handler, we can reduce the number of interrupts. We also don't need any
status variables as the registers are still valid.

Also, notice that if budget pkts are received, the next call to fec_enet_rx_napi
will now continue to receive the previously pending packets.

Signed-off-by: Troy Kisky <redacted>
---
 drivers/net/ethernet/freescale/fec.h      |   6 +-
 drivers/net/ethernet/freescale/fec_main.c | 127 ++++++++++++----------------
--
 2 files changed, 50 insertions(+), 83 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec.h

b/drivers/net/ethernet/freescale/fec.h
index 195122e..001200b 100644

--- a/drivers/net/ethernet/freescale/fec.h
+++ b/drivers/net/ethernet/freescale/fec.h

@@ -505,11 +505,7 @@ struct fec_enet_private {

     unsigned int total_tx_ring_size;
     unsigned int total_rx_ring_size;
-
-    unsigned long work_tx;
-    unsigned long work_rx;
-    unsigned long work_ts;
-    unsigned long work_mdio;
+    uint    events;

     struct  platform_device *pdev;

diff --git a/drivers/net/ethernet/freescale/fec_main.c

b/drivers/net/ethernet/freescale/fec_main.c
index c517194..4a218b9 100644

--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c

@@ -70,8 +70,6 @@ static void fec_enet_itr_coal_init(struct net_device

*ndev);

 #define DRIVER_NAME "fec"

-#define FEC_ENET_GET_QUQUE(_x) ((_x == 0) ? 1 : ((_x == 1) ? 2 : 0))
-
 /* Pause frame feild and FIFO threshold */
 #define FEC_ENET_FCE        (1 << 5)
 #define FEC_ENET_RSEM_V     0x84

@@ -1257,21 +1255,6 @@ static void fec_txq(struct net_device *ndev, struct

fec_enet_private *fep,
             writel(0, txq->bd.reg_desc_active);
 }

-static void
-fec_enet_tx(struct net_device *ndev)
-{
-    struct fec_enet_private *fep = netdev_priv(ndev);
-    struct fec_enet_priv_tx_q *txq;
-    u16 queue_id;
-    /* First process class A queue, then Class B and Best Effort queue */
-    for_each_set_bit(queue_id, &fep->work_tx, FEC_ENET_MAX_TX_QS)
{
-            clear_bit(queue_id, &fep->work_tx);
-            txq = fep->tx_queue[FEC_ENET_GET_QUQUE(queue_id)];
-            fec_txq(ndev, fep, txq);
-    }
-    return;
-}
-
 static int
 fec_enet_new_rxbdp(struct net_device *ndev, struct bufdesc *bdp, struct
sk_buff *skb)  { @@ -1504,92 +1487,80 @@ rx_processing_done:
     return pkt_received;
 }

-static int
-fec_enet_rx(struct net_device *ndev, int budget) -{
-    int     pkt_received = 0;
-    u16     queue_id;
-    struct fec_enet_private *fep = netdev_priv(ndev);
-    struct fec_enet_priv_rx_q *rxq;
-
-    for_each_set_bit(queue_id, &fep->work_rx, FEC_ENET_MAX_RX_QS)
{
-            clear_bit(queue_id, &fep->work_rx);
-            rxq = fep->rx_queue[FEC_ENET_GET_QUQUE(queue_id)];
-            pkt_received += fec_rxq(ndev, fep, rxq, budget -
pkt_received);
-    }
-    return pkt_received;
-}
-
-static bool
-fec_enet_collect_events(struct fec_enet_private *fep, uint int_events) -{
-    if (int_events == 0)
-            return false;
-
-    if (int_events & FEC_ENET_RXF_0)
-            fep->work_rx |= (1 << 2);
-    if (int_events & FEC_ENET_RXF_1)
-            fep->work_rx |= (1 << 0);
-    if (int_events & FEC_ENET_RXF_2)
-            fep->work_rx |= (1 << 1);
-
-    if (int_events & FEC_ENET_TXF_0)
-            fep->work_tx |= (1 << 2);
-    if (int_events & FEC_ENET_TXF_1)
-            fep->work_tx |= (1 << 0);
-    if (int_events & FEC_ENET_TXF_2)
-            fep->work_tx |= (1 << 1);
-
-    return true;
-}
-
 static irqreturn_t
 fec_enet_interrupt(int irq, void *dev_id)  {
     struct net_device *ndev = dev_id;
     struct fec_enet_private *fep = netdev_priv(ndev);
-    uint int_events;
-    irqreturn_t ret = IRQ_NONE;
+    uint eir = readl(fep->hwp + FEC_IEVENT);
+    uint int_events = eir & readl(fep->hwp + FEC_IMASK);

-    int_events = readl(fep->hwp + FEC_IEVENT);
-    writel(int_events, fep->hwp + FEC_IEVENT);
-    fec_enet_collect_events(fep, int_events);
-
-    if ((fep->work_tx || fep->work_rx) && fep->link) {
-            ret = IRQ_HANDLED;
+    if (!int_events)
+            return IRQ_NONE;

+    if (int_events & (FEC_ENET_RXF | FEC_ENET_TXF)) {
             if (napi_schedule_prep(&fep->napi)) {
                     /* Disable the NAPI interrupts */
                     writel(FEC_NAPI_IMASK, fep->hwp + FEC_IMASK);
                     __napi_schedule(&fep->napi);
+                    int_events &= ~(FEC_ENET_RXF | FEC_ENET_TXF);
+                    if (!int_events)
+                            return IRQ_HANDLED;
+            } else {
+                    fep->events |= int_events;
+                    pr_info("%s: couldn't schedule NAPI\n", __func__);
             }
     }

-    if (int_events & FEC_ENET_MII) {
-            ret = IRQ_HANDLED;
+    writel(int_events, fep->hwp + FEC_IEVENT);
+    if (int_events & FEC_ENET_MII)
             complete(&fep->mdio_done);
-    }

-    if (fep->ptp_clock)
+    if ((int_events & FEC_ENET_TS_TIMER) && fep->ptp_clock)
             fec_ptp_check_pps_event(fep);
-

This is error in here.  FEC compare timer event is not TS timer.

So when should fec_ptp_check_pps_event be called ? On every interrupt ?

Compare event is not showed in EIR register.  Need check TCSR, please
see below code.

uint fec_ptp_check_pps_event(struct fec_enet_private *fep)
{
xx
 val = readl(fep->hwp + FEC_TCSR(channel));
        if (val & FEC_T_TF_MASK) {
}

If napi is active, it is going to be delayed for a very long time.
Should it be moved to the napi routine?