gianfar: Avoid unnecessary reg accesses in adjust_link()

For phy devices that don't issue interrupts upon link
state changes, phylib polls the link state resulting in
repeated calls to adjust_link(), even if the link state
didn't change.  As a result, some mac registers are
repeatedly read and written with the same values, which
is not ok.

To fix this, adjust_link() has been refactored to check
first whether the link state has changed and to take action
only if needed, updating mac registers and local state
variables.  The 'new_state' local flag, set if one of the
link params changed (link, speed or duplex), has been
rendered useless and removed by this refactoring.

Signed-off-by: Claudiu Manoil <claudiu.manoil@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 113 insertions, 110 deletions

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 9125d9abf099..e2d42475b006 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -121,6 +121,7 @@ static irqreturn_t gfar_error(int irq, void *dev_id);
 static irqreturn_t gfar_transmit(int irq, void *dev_id);
 static irqreturn_t gfar_interrupt(int irq, void *dev_id);
 static void adjust_link(struct net_device *dev);
+static noinline void gfar_update_link_state(struct gfar_private *priv);
 static int init_phy(struct net_device *dev);
 static int gfar_probe(struct platform_device *ofdev);
 static int gfar_remove(struct platform_device *ofdev);
@@ -3076,41 +3077,6 @@ static irqreturn_t gfar_interrupt(int irq, void *grp_id)
         return IRQ_HANDLED;
 }
 
-static u32 gfar_get_flowctrl_cfg(struct gfar_private *priv)
-{
-        struct phy_device *phydev = priv->phydev;
-        u32 val = 0;
-
-        if (!phydev->duplex)
-                return val;
-
-        if (!priv->pause_aneg_en) {
-                if (priv->tx_pause_en)
-                        val |= MACCFG1_TX_FLOW;
-                if (priv->rx_pause_en)
-                        val |= MACCFG1_RX_FLOW;
-        } else {
-                u16 lcl_adv, rmt_adv;
-                u8 flowctrl;
-                /* get link partner capabilities */
-                rmt_adv = 0;
-                if (phydev->pause)
-                        rmt_adv = LPA_PAUSE_CAP;
-                if (phydev->asym_pause)
-                        rmt_adv |= LPA_PAUSE_ASYM;
-
-                lcl_adv = mii_advertise_flowctrl(phydev->advertising);
-
-                flowctrl = mii_resolve_flowctrl_fdx(lcl_adv, rmt_adv);
-                if (flowctrl & FLOW_CTRL_TX)
-                        val |= MACCFG1_TX_FLOW;
-                if (flowctrl & FLOW_CTRL_RX)
-                        val |= MACCFG1_RX_FLOW;
-        }
-
-        return val;
-}
-
 /* Called every time the controller might need to be made
  * aware of new link state.  The PHY code conveys this
  * information through variables in the phydev structure, and this
@@ -3120,83 +3086,12 @@ static u32 gfar_get_flowctrl_cfg(struct gfar_private *priv)
 static void adjust_link(struct net_device *dev)
 {
         struct gfar_private *priv = netdev_priv(dev);
-        struct gfar __iomem *regs = priv->gfargrp[0].regs;
         struct phy_device *phydev = priv->phydev;
-        int new_state = 0;
 
-        if (test_bit(GFAR_RESETTING, &priv->state))
-                return;
-
-        if (phydev->link) {
-                u32 tempval1 = gfar_read(&regs->maccfg1);
-                u32 tempval = gfar_read(&regs->maccfg2);
-                u32 ecntrl = gfar_read(&regs->ecntrl);
-
-                /* Now we make sure that we can be in full duplex mode.
-                 * If not, we operate in half-duplex mode.
-                 */
-                if (phydev->duplex != priv->oldduplex) {
-                        new_state = 1;
-                        if (!(phydev->duplex))
-                                tempval &= ~(MACCFG2_FULL_DUPLEX);
-                        else
-                                tempval |= MACCFG2_FULL_DUPLEX;
-
-                        priv->oldduplex = phydev->duplex;
-                }
-
-                if (phydev->speed != priv->oldspeed) {
-                        new_state = 1;
-                        switch (phydev->speed) {
-                        case 1000:
-                                tempval =
-                                    ((tempval & ~(MACCFG2_IF)) | MACCFG2_GMII);
-
-                                ecntrl &= ~(ECNTRL_R100);
-                                break;
-                        case 100:
-                        case 10:
-                                tempval =
-                                    ((tempval & ~(MACCFG2_IF)) | MACCFG2_MII);
-
-                                /* Reduced mode distinguishes
-                                 * between 10 and 100
-                                 */
-                                if (phydev->speed == SPEED_100)
-                                        ecntrl |= ECNTRL_R100;
-                                else
-                                        ecntrl &= ~(ECNTRL_R100);
-                                break;
-                        default:
-                                netif_warn(priv, link, dev,
-                                           "Ack!  Speed (%d) is not 10/100/1000!\n",
-                                           phydev->speed);
-                                break;
-                        }
-
-                        priv->oldspeed = phydev->speed;
-                }
-
-                tempval1 &= ~(MACCFG1_TX_FLOW | MACCFG1_RX_FLOW);
-                tempval1 |= gfar_get_flowctrl_cfg(priv);
-
-                gfar_write(&regs->maccfg1, tempval1);
-                gfar_write(&regs->maccfg2, tempval);
-                gfar_write(&regs->ecntrl, ecntrl);
-
-                if (!priv->oldlink) {
-                        new_state = 1;
-                        priv->oldlink = 1;
-                }
-        } else if (priv->oldlink) {
-                new_state = 1;
-                priv->oldlink = 0;
-                priv->oldspeed = 0;
-                priv->oldduplex = -1;
-        }
-
-        if (new_state && netif_msg_link(priv))
-                phy_print_status(phydev);
+        if (unlikely(phydev->link != priv->oldlink ||
+                     phydev->duplex != priv->oldduplex ||
+                     phydev->speed != priv->oldspeed))
+                gfar_update_link_state(priv);
 }
 
 /* Update the hash table based on the current list of multicast
@@ -3442,6 +3337,114 @@ static irqreturn_t gfar_error(int irq, void *grp_id)
         return IRQ_HANDLED;
 }
 
+static u32 gfar_get_flowctrl_cfg(struct gfar_private *priv)
+{
+        struct phy_device *phydev = priv->phydev;
+        u32 val = 0;
+
+        if (!phydev->duplex)
+                return val;
+
+        if (!priv->pause_aneg_en) {
+                if (priv->tx_pause_en)
+                        val |= MACCFG1_TX_FLOW;
+                if (priv->rx_pause_en)
+                        val |= MACCFG1_RX_FLOW;
+        } else {
+                u16 lcl_adv, rmt_adv;
+                u8 flowctrl;
+                /* get link partner capabilities */
+                rmt_adv = 0;
+                if (phydev->pause)
+                        rmt_adv = LPA_PAUSE_CAP;
+                if (phydev->asym_pause)
+                        rmt_adv |= LPA_PAUSE_ASYM;
+
+                lcl_adv = mii_advertise_flowctrl(phydev->advertising);
+
+                flowctrl = mii_resolve_flowctrl_fdx(lcl_adv, rmt_adv);
+                if (flowctrl & FLOW_CTRL_TX)
+                        val |= MACCFG1_TX_FLOW;
+                if (flowctrl & FLOW_CTRL_RX)
+                        val |= MACCFG1_RX_FLOW;
+        }
+
+        return val;
+}
+
+static noinline void gfar_update_link_state(struct gfar_private *priv)
+{
+        struct gfar __iomem *regs = priv->gfargrp[0].regs;
+        struct phy_device *phydev = priv->phydev;
+
+        if (unlikely(test_bit(GFAR_RESETTING, &priv->state)))
+                return;
+
+        if (phydev->link) {
+                u32 tempval1 = gfar_read(&regs->maccfg1);
+                u32 tempval = gfar_read(&regs->maccfg2);
+                u32 ecntrl = gfar_read(&regs->ecntrl);
+
+                if (phydev->duplex != priv->oldduplex) {
+                        if (!(phydev->duplex))
+                                tempval &= ~(MACCFG2_FULL_DUPLEX);
+                        else
+                                tempval |= MACCFG2_FULL_DUPLEX;
+
+                        priv->oldduplex = phydev->duplex;
+                }
+
+                if (phydev->speed != priv->oldspeed) {
+                        switch (phydev->speed) {
+                        case 1000:
+                                tempval =
+                                    ((tempval & ~(MACCFG2_IF)) | MACCFG2_GMII);
+
+                                ecntrl &= ~(ECNTRL_R100);
+                                break;
+                        case 100:
+                        case 10:
+                                tempval =
+                                    ((tempval & ~(MACCFG2_IF)) | MACCFG2_MII);
+
+                                /* Reduced mode distinguishes
+                                 * between 10 and 100
+                                 */
+                                if (phydev->speed == SPEED_100)
+                                        ecntrl |= ECNTRL_R100;
+                                else
+                                        ecntrl &= ~(ECNTRL_R100);
+                                break;
+                        default:
+                                netif_warn(priv, link, priv->ndev,
+                                           "Ack!  Speed (%d) is not 10/100/1000!\n",
+                                           phydev->speed);
+                                break;
+                        }
+
+                        priv->oldspeed = phydev->speed;
+                }
+
+                tempval1 &= ~(MACCFG1_TX_FLOW | MACCFG1_RX_FLOW);
+                tempval1 |= gfar_get_flowctrl_cfg(priv);
+
+                gfar_write(&regs->maccfg1, tempval1);
+                gfar_write(&regs->maccfg2, tempval);
+                gfar_write(&regs->ecntrl, ecntrl);
+
+                if (!priv->oldlink)
+                        priv->oldlink = 1;
+
+        } else if (priv->oldlink) {
+                priv->oldlink = 0;
+                priv->oldspeed = 0;
+                priv->oldduplex = -1;
+        }
+
+        if (netif_msg_link(priv))
+                phy_print_status(phydev);
+}
+
 static struct of_device_id gfar_match[] =
 {
         {