net: qcom/emac: do not use hardware mdio automatic polling

Use software polling (PHY_POLL) to check for link state changes instead
of relying on the EMAC's hardware polling feature.  Some PHY drivers
are unable to get a functioning link because the HW polling is not
robust enough.

The EMAC is able to poll the PHY on the MDIO bus looking for link state
changes (via the Link Status bit in the Status Register at address 0x1).
When the link state changes, the EMAC triggers an interrupt and tells the
driver what the new state is.  The feature eliminates the need for
software to poll the MDIO bus.

Unfortunately, this feature is incompatible with phylib, because it
ignores everything that the PHY core and PHY drivers are trying to do.
In particular:

1. It assumes a compatible register set, so PHYs with different registers
   may not work.

2. It doesn't allow for hardware errata that have work-arounds implemented
   in the PHY driver.

3. It doesn't support multiple register pages. If the PHY core switches
   the register set to another page, the EMAC won't know the page has
   changed and will still attempt to read the same PHY register.

4. It only checks the copper side of the link, not the SGMII side.  Some
   PHY drivers (e.g. at803x) may also check the SGMII side, and
   report the link as not ready during autonegotiation if the SGMII link
   is still down.  Phylib then waits for another interrupt to query
   the PHY again, but the EMAC won't send another interrupt because it
   thinks the link is up.

Cc: stable@vger.kernel.org # 4.11.x
Tested-by: Manoj Iyer <manoj.iyer@canonical.com>
Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qualcomm/emac/emac-mac.c

@@ -931,7 +931,7 @@ int emac_mac_up(struct emac_adapter *adpt)
 	emac_mac_config(adpt);
 	emac_mac_rx_descs_refill(adpt, &adpt->rx_q);
 
-	adpt->phydev->irq = PHY_IGNORE_INTERRUPT;
+	adpt->phydev->irq = PHY_POLL;
 	ret = phy_connect_direct(netdev, adpt->phydev, emac_adjust_link,
 				 PHY_INTERFACE_MODE_SGMII);
 	if (ret) {

drivers/net/ethernet/qualcomm/emac/emac-phy.c

@@ -13,15 +13,11 @@
 /* Qualcomm Technologies, Inc. EMAC PHY Controller driver.
  */
 
-#include <linux/module.h>
-#include <linux/of.h>
-#include <linux/of_net.h>
 #include <linux/of_mdio.h>
 #include <linux/phy.h>
 #include <linux/iopoll.h>
 #include <linux/acpi.h>
 #include "emac.h"
-#include "emac-mac.h"
 
 /* EMAC base register offsets */
 #define EMAC_MDIO_CTRL                                        0x001414
@@ -52,62 +48,10 @@
 
 #define MDIO_WAIT_TIMES                                           1000
 
-#define EMAC_LINK_SPEED_DEFAULT (\
-		EMAC_LINK_SPEED_10_HALF  |\
-		EMAC_LINK_SPEED_10_FULL  |\
-		EMAC_LINK_SPEED_100_HALF |\
-		EMAC_LINK_SPEED_100_FULL |\
-		EMAC_LINK_SPEED_1GB_FULL)
-
-/**
- * emac_phy_mdio_autopoll_disable() - disable mdio autopoll
- * @adpt: the emac adapter
- *
- * The autopoll feature takes over the MDIO bus.  In order for
- * the PHY driver to be able to talk to the PHY over the MDIO
- * bus, we need to temporarily disable the autopoll feature.
- */
-static int emac_phy_mdio_autopoll_disable(struct emac_adapter *adpt)
-{
-	u32 val;
-
-	/* disable autopoll */
-	emac_reg_update32(adpt->base + EMAC_MDIO_CTRL, MDIO_AP_EN, 0);
-
-	/* wait for any mdio polling to complete */
-	if (!readl_poll_timeout(adpt->base + EMAC_MDIO_CTRL, val,
-				!(val & MDIO_BUSY), 100, MDIO_WAIT_TIMES * 100))
-		return 0;
-
-	/* failed to disable; ensure it is enabled before returning */
-	emac_reg_update32(adpt->base + EMAC_MDIO_CTRL, 0, MDIO_AP_EN);
-
-	return -EBUSY;
-}
-
-/**
- * emac_phy_mdio_autopoll_disable() - disable mdio autopoll
- * @adpt: the emac adapter
- *
- * The EMAC has the ability to poll the external PHY on the MDIO
- * bus for link state changes.  This eliminates the need for the
- * driver to poll the phy.  If if the link state does change,
- * the EMAC issues an interrupt on behalf of the PHY.
- */
-static void emac_phy_mdio_autopoll_enable(struct emac_adapter *adpt)
-{
-	emac_reg_update32(adpt->base + EMAC_MDIO_CTRL, 0, MDIO_AP_EN);
-}
-
 static int emac_mdio_read(struct mii_bus *bus, int addr, int regnum)
 {
 	struct emac_adapter *adpt = bus->priv;
 	u32 reg;
-	int ret;
-
-	ret = emac_phy_mdio_autopoll_disable(adpt);
-	if (ret)
-		return ret;
 
 	emac_reg_update32(adpt->base + EMAC_PHY_STS, PHY_ADDR_BMSK,
 			  (addr << PHY_ADDR_SHFT));
@@ -122,24 +66,15 @@ static int emac_mdio_read(struct mii_bus *bus, int addr, int regnum)
 	if (readl_poll_timeout(adpt->base + EMAC_MDIO_CTRL, reg,
 			       !(reg & (MDIO_START | MDIO_BUSY)),
 			       100, MDIO_WAIT_TIMES * 100))
-		ret = -EIO;
-	else
-		ret = (reg >> MDIO_DATA_SHFT) & MDIO_DATA_BMSK;
+		return -EIO;
 
-	emac_phy_mdio_autopoll_enable(adpt);
-
-	return ret;
+	return (reg >> MDIO_DATA_SHFT) & MDIO_DATA_BMSK;
 }
 
 static int emac_mdio_write(struct mii_bus *bus, int addr, int regnum, u16 val)
 {
 	struct emac_adapter *adpt = bus->priv;
 	u32 reg;
-	int ret;
-
-	ret = emac_phy_mdio_autopoll_disable(adpt);
-	if (ret)
-		return ret;
 
 	emac_reg_update32(adpt->base + EMAC_PHY_STS, PHY_ADDR_BMSK,
 			  (addr << PHY_ADDR_SHFT));
@@ -155,11 +90,9 @@ static int emac_mdio_write(struct mii_bus *bus, int addr, int regnum, u16 val)
 	if (readl_poll_timeout(adpt->base + EMAC_MDIO_CTRL, reg,
 			       !(reg & (MDIO_START | MDIO_BUSY)), 100,
 			       MDIO_WAIT_TIMES * 100))
-		ret = -EIO;
+		return -EIO;
 
-	emac_phy_mdio_autopoll_enable(adpt);
-
-	return ret;
+	return 0;
 }
 
 /* Configure the MDIO bus and connect the external PHY */

drivers/net/ethernet/qualcomm/emac/emac.c

@@ -50,19 +50,7 @@
 #define DMAR_DLY_CNT_DEF				    15
 #define DMAW_DLY_CNT_DEF				     4
 
-#define IMR_NORMAL_MASK         (\
-		ISR_ERROR       |\
-		ISR_GPHY_LINK   |\
-		ISR_TX_PKT      |\
-		GPHY_WAKEUP_INT)
-
-#define IMR_EXTENDED_MASK       (\
-		SW_MAN_INT      |\
-		ISR_OVER        |\
-		ISR_ERROR       |\
-		ISR_GPHY_LINK   |\
-		ISR_TX_PKT      |\
-		GPHY_WAKEUP_INT)
+#define IMR_NORMAL_MASK		(ISR_ERROR | ISR_OVER | ISR_TX_PKT)
 
 #define ISR_TX_PKT      (\
 	TX_PKT_INT      |\
@@ -70,10 +58,6 @@
 	TX_PKT_INT2     |\
 	TX_PKT_INT3)
 
-#define ISR_GPHY_LINK        (\
-	GPHY_LINK_UP_INT     |\
-	GPHY_LINK_DOWN_INT)
-
 #define ISR_OVER        (\
 	RFD0_UR_INT     |\
 	RFD1_UR_INT     |\
@@ -187,10 +171,6 @@ irqreturn_t emac_isr(int _irq, void *data)
 	if (status & ISR_OVER)
 		net_warn_ratelimited("warning: TX/RX overflow\n");
 
-	/* link event */
-	if (status & ISR_GPHY_LINK)
-		phy_mac_interrupt(adpt->phydev, !!(status & GPHY_LINK_UP_INT));
-
 exit:
 	/* enable the interrupt */
 	writel(irq->mask, adpt->base + EMAC_INT_MASK);