stmmac: add the initial tx coalesce schema

This patch adds a new schema used for mitigating the
number of transmit interrupts.
It is based on a SW timer and a threshold value.
The timer is used to periodically call the stmmac_tx_clean
function; the threshold is used for setting the IC (Interrupt
on Completion bit). The ISR will then invoke the poll method.
Also the patch improves some ethtool stat fields.

V2: review the logic to manage the IC bit in the TDESC
that was bugged because it didn't take care about the
fragments. Also fix the tx_count_frames that has not to be
limited to TX DMA ring. Thanks to Ben Hutchings.

V3: removed the spin_lock irqsave/restore as D. Miller suggested.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 111 insertions, 62 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
index 719be3912aa9..723e9035f275 100644
--- a/drivers/net/ethernet/stmicro/stmmac/common.h
+++ b/drivers/net/ethernet/stmicro/stmmac/common.h
@@ -95,9 +95,12 @@ struct stmmac_extra_stats {
         unsigned long threshold;
         unsigned long tx_pkt_n;
         unsigned long rx_pkt_n;
-        unsigned long poll_n;
-        unsigned long sched_timer_n;
         unsigned long normal_irq_n;
+        unsigned long rx_normal_irq_n;
+        unsigned long napi_poll;
+        unsigned long tx_normal_irq_n;
+        unsigned long tx_clean;
+        unsigned long tx_reset_ic_bit;
         unsigned long mmc_tx_irq_n;
         unsigned long mmc_rx_irq_n;
         unsigned long mmc_rx_csum_offload_irq_n;
@@ -162,6 +165,12 @@ struct stmmac_extra_stats {
 #define DMA_HW_FEAT_ACTPHYIF    0x70000000 /* Active/selected PHY interface */
 #define DEFAULT_DMA_PBL         8
 
+/* Tx coalesce parameters */
+#define STMMAC_COAL_TX_TIMER    40000
+#define STMMAC_MAX_COAL_TX_TICK 100000
+#define STMMAC_TX_MAX_FRAMES    256
+#define STMMAC_TX_FRAMES        64
+
 enum rx_frame_status { /* IPC status */
         good_frame = 0,
         discard_frame = 1,
@@ -169,10 +178,11 @@ enum rx_frame_status { /* IPC status */
         llc_snap = 4,
 };
 
-enum tx_dma_irq_status {
-        tx_hard_error = 1,
-        tx_hard_error_bump_tc = 2,
-        handle_tx_rx = 3,
+enum dma_irq_status {
+        tx_hard_error = 0x1,
+        tx_hard_error_bump_tc = 0x2,
+        handle_rx = 0x4,
+        handle_tx = 0x8,
 };
 
 enum core_specific_irq_mask {
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
index 4e0e18a44fcc..73766e655011 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
@@ -206,9 +206,10 @@ int dwmac_dma_interrupt(void __iomem *ioaddr,
         /* TX/RX NORMAL interrupts */
         if (intr_status & DMA_STATUS_NIS) {
                 x->normal_irq_n++;
-                if (likely((intr_status & DMA_STATUS_RI) ||
-                         (intr_status & (DMA_STATUS_TI))))
-                                ret = handle_tx_rx;
+                if (likely(intr_status & DMA_STATUS_RI))
+                        ret |= handle_rx;
+                if (intr_status & (DMA_STATUS_TI))
+                        ret |= handle_tx;
         }
         /* Optional hardware blocks, interrupts should be disabled */
         if (unlikely(intr_status &
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 5f89415bdbc8..01b34517ca8e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -87,6 +87,10 @@ struct stmmac_priv {
         int eee_enabled;
         int eee_active;
         int tx_lpi_timer;
+        struct timer_list txtimer;
+        u32 tx_count_frames;
+        u32 tx_coal_frames;
+        u32 tx_coal_timer;
 };
 
 extern int phyaddr;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
index 76fd61aa005f..15cb6ee6ee41 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
@@ -90,10 +90,12 @@ static const struct stmmac_stats stmmac_gstrings_stats[] = {
         STMMAC_STAT(threshold),
         STMMAC_STAT(tx_pkt_n),
         STMMAC_STAT(rx_pkt_n),
-        STMMAC_STAT(poll_n),
-        STMMAC_STAT(sched_timer_n),
-        STMMAC_STAT(normal_irq_n),
         STMMAC_STAT(normal_irq_n),
+        STMMAC_STAT(rx_normal_irq_n),
+        STMMAC_STAT(napi_poll),
+        STMMAC_STAT(tx_normal_irq_n),
+        STMMAC_STAT(tx_clean),
+        STMMAC_STAT(tx_reset_ic_bit),
         STMMAC_STAT(mmc_tx_irq_n),
         STMMAC_STAT(mmc_rx_irq_n),
         STMMAC_STAT(mmc_rx_csum_offload_irq_n),
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 777234cb30d6..d9d68649bdaa 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -137,6 +137,8 @@ static int stmmac_init_fs(struct net_device *dev);
 static void stmmac_exit_fs(void);
 #endif
 
+#define STMMAC_COAL_TIMER(x) (jiffies + usecs_to_jiffies(x))
+
 /**
  * stmmac_verify_args - verify the driver parameters.
  * Description: it verifies if some wrong parameter is passed to the driver.
@@ -688,16 +690,18 @@ static void stmmac_dma_operation_mode(struct stmmac_priv *priv)
 }
 
 /**
- * stmmac_tx:
- * @priv: private driver structure
+ * stmmac_tx_clean:
+ * @priv: private data pointer
  * Description: it reclaims resources after transmission completes.
  */
-static void stmmac_tx(struct stmmac_priv *priv)
+static void stmmac_tx_clean(struct stmmac_priv *priv)
 {
         unsigned int txsize = priv->dma_tx_size;
 
         spin_lock(&priv->tx_lock);
 
+        priv->xstats.tx_clean++;
+
         while (priv->dirty_tx != priv->cur_tx) {
                 int last;
                 unsigned int entry = priv->dirty_tx % txsize;
@@ -757,40 +761,16 @@ static void stmmac_tx(struct stmmac_priv *priv)
         spin_unlock(&priv->tx_lock);
 }
 
-static inline void stmmac_enable_irq(struct stmmac_priv *priv)
+static inline void stmmac_enable_dma_irq(struct stmmac_priv *priv)
 {
         priv->hw->dma->enable_dma_irq(priv->ioaddr);
 }
 
-static inline void stmmac_disable_irq(struct stmmac_priv *priv)
+static inline void stmmac_disable_dma_irq(struct stmmac_priv *priv)
 {
         priv->hw->dma->disable_dma_irq(priv->ioaddr);
 }
 
-static int stmmac_has_work(struct stmmac_priv *priv)
-{
-        unsigned int has_work = 0;
-        int rxret, tx_work = 0;
-
-        rxret = priv->hw->desc->get_rx_owner(priv->dma_rx +
-                (priv->cur_rx % priv->dma_rx_size));
-
-        if (priv->dirty_tx != priv->cur_tx)
-                tx_work = 1;
-
-        if (likely(!rxret || tx_work))
-                has_work = 1;
-
-        return has_work;
-}
-
-static inline void _stmmac_schedule(struct stmmac_priv *priv)
-{
-        if (likely(stmmac_has_work(priv))) {
-                stmmac_disable_irq(priv);
-                napi_schedule(&priv->napi);
-        }
-}
 
 /**
  * stmmac_tx_err:
@@ -813,16 +793,18 @@ static void stmmac_tx_err(struct stmmac_priv *priv)
         netif_wake_queue(priv->dev);
 }
 
-
 static void stmmac_dma_interrupt(struct stmmac_priv *priv)
 {
         int status;
 
         status = priv->hw->dma->dma_interrupt(priv->ioaddr, &priv->xstats);
-        if (likely(status == handle_tx_rx))
-                _stmmac_schedule(priv);
-
-        else if (unlikely(status == tx_hard_error_bump_tc)) {
+        if (likely((status & handle_rx)) || (status & handle_tx)) {
+                if (likely(napi_schedule_prep(&priv->napi))) {
+                        stmmac_disable_dma_irq(priv);
+                        __napi_schedule(&priv->napi);
+                }
+        }
+        if (unlikely(status & tx_hard_error_bump_tc)) {
                 /* Try to bump up the dma threshold on this failure */
                 if (unlikely(tc != SF_DMA_MODE) && (tc <= 256)) {
                         tc += 64;
@@ -938,7 +920,6 @@ static int stmmac_get_hw_features(struct stmmac_priv *priv)
                 /* Alternate (enhanced) DESC mode*/
                 priv->dma_cap.enh_desc =
                         (hw_cap & DMA_HW_FEAT_ENHDESSEL) >> 24;
-
         }
 
         return hw_cap;
@@ -980,6 +961,38 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
 }
 
 /**
+ * stmmac_tx_timer:
+ * @data: data pointer
+ * Description:
+ * This is the timer handler to directly invoke the stmmac_tx_clean.
+ */
+static void stmmac_tx_timer(unsigned long data)
+{
+        struct stmmac_priv *priv = (struct stmmac_priv *)data;
+
+        stmmac_tx_clean(priv);
+}
+
+/**
+ * stmmac_tx_timer:
+ * @priv: private data structure
+ * Description:
+ * This inits the transmit coalesce parameters: i.e. timer rate,
+ * timer handler and default threshold used for enabling the
+ * interrupt on completion bit.
+ */
+static void stmmac_init_tx_coalesce(struct stmmac_priv *priv)
+{
+        priv->tx_coal_frames = STMMAC_TX_FRAMES;
+        priv->tx_coal_timer = STMMAC_COAL_TX_TIMER;
+        init_timer(&priv->txtimer);
+        priv->txtimer.expires = STMMAC_COAL_TIMER(priv->tx_coal_timer);
+        priv->txtimer.data = (unsigned long)priv;
+        priv->txtimer.function = stmmac_tx_timer;
+        add_timer(&priv->txtimer);
+}
+
+/**
  *  stmmac_open - open entry point of the driver
  *  @dev : pointer to the device structure.
  *  Description:
@@ -1091,6 +1104,8 @@ static int stmmac_open(struct net_device *dev)
         priv->tx_lpi_timer = STMMAC_DEFAULT_TWT_LS_TIMER;
         priv->eee_enabled = stmmac_eee_init(priv);
 
+        stmmac_init_tx_coalesce(priv);
+
         napi_enable(&priv->napi);
         netif_start_queue(dev);
 
@@ -1136,6 +1151,8 @@ static int stmmac_release(struct net_device *dev)
 
         napi_disable(&priv->napi);
 
+        del_timer_sync(&priv->txtimer);
+
         /* Free the IRQ lines */
         free_irq(dev->irq, dev);
         if (priv->wol_irq != dev->irq)
@@ -1198,11 +1215,13 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 
 #ifdef STMMAC_XMIT_DEBUG
         if ((skb->len > ETH_FRAME_LEN) || nfrags)
-                pr_info("stmmac xmit:\n"
-                       "\tskb addr %p - len: %d - nopaged_len: %d\n"
-                       "\tn_frags: %d - ip_summed: %d - %s gso\n",
-                       skb, skb->len, nopaged_len, nfrags, skb->ip_summed,
-                       !skb_is_gso(skb) ? "isn't" : "is");
+                pr_debug("stmmac xmit: [entry %d]\n"
+                         "\tskb addr %p - len: %d - nopaged_len: %d\n"
+                         "\tn_frags: %d - ip_summed: %d - %s gso\n"
+                         "\ttx_count_frames %d\n", entry,
+                         skb, skb->len, nopaged_len, nfrags, skb->ip_summed,
+                         !skb_is_gso(skb) ? "isn't" : "is",
+                         priv->tx_count_frames);
 #endif
 
         csum_insertion = (skb->ip_summed == CHECKSUM_PARTIAL);
@@ -1212,9 +1231,9 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 
 #ifdef STMMAC_XMIT_DEBUG
         if ((nfrags > 0) || (skb->len > ETH_FRAME_LEN))
-                pr_debug("stmmac xmit: skb len: %d, nopaged_len: %d,\n"
-                       "\t\tn_frags: %d, ip_summed: %d\n",
-                       skb->len, nopaged_len, nfrags, skb->ip_summed);
+                pr_debug("\tskb len: %d, nopaged_len: %d,\n"
+                         "\t\tn_frags: %d, ip_summed: %d\n",
+                         skb->len, nopaged_len, nfrags, skb->ip_summed);
 #endif
         priv->tx_skbuff[entry] = skb;
 
@@ -1245,10 +1264,24 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
                 wmb();
         }
 
-        /* Interrupt on completition only for the latest segment */
+        /* Finalize the latest segment. */
         priv->hw->desc->close_tx_desc(desc);
 
         wmb();
+        /* According to the coalesce parameter the IC bit for the latest
+         * segment could be reset and the timer re-started to invoke the
+         * stmmac_tx function. This approach takes care about the fragments.
+         */
+        priv->tx_count_frames += nfrags + 1;
+        if (priv->tx_coal_frames > priv->tx_count_frames) {
+                priv->hw->desc->clear_tx_ic(desc);
+                priv->xstats.tx_reset_ic_bit++;
+                TX_DBG("\t[entry %d]: tx_count_frames %d\n", entry,
+                       priv->tx_count_frames);
+                mod_timer(&priv->txtimer,
+                          STMMAC_COAL_TIMER(priv->tx_coal_timer));
+        } else
+                priv->tx_count_frames = 0;
 
         /* To avoid raise condition */
         priv->hw->desc->set_tx_owner(first);
@@ -1419,21 +1452,20 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit)
  *  @budget : maximum number of packets that the current CPU can receive from
  *            all interfaces.
  *  Description :
- *   This function implements the the reception process.
- *   Also it runs the TX completion thread
+ *  To look at the incoming frames and clear the tx resources.
  */
 static int stmmac_poll(struct napi_struct *napi, int budget)
 {
         struct stmmac_priv *priv = container_of(napi, struct stmmac_priv, napi);
         int work_done = 0;
 
-        priv->xstats.poll_n++;
-        stmmac_tx(priv);
-        work_done = stmmac_rx(priv, budget);
+        priv->xstats.napi_poll++;
+        stmmac_tx_clean(priv);
 
+        work_done = stmmac_rx(priv, budget);
         if (work_done < budget) {
                 napi_complete(napi);
-                stmmac_enable_irq(priv);
+                stmmac_enable_dma_irq(priv);
         }
         return work_done;
 }