[PATCH] phy/marvell: prevent unneeded page switching

[Frank de Brabander <debrabander@gmail.com>]

marvell_read_status() no longer first switches to the fiber page, instead
looks at the already active register page first. In case the link is down,
switches to the other (fiber/copper) register page.

Unneeded register page switching of the Marvell 88E1510 PHY can cause
the ethernet driver to register a link down & up event.

Signed-off-by: Frank de Brabander <debrabander@gmail.com>
---
 drivers/net/phy/marvell.c | 59 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 38 insertions(+), 21 deletions(-)

diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
index abb7876..31de2db 100644
--- a/drivers/net/phy/marvell.c
+++ b/drivers/net/phy/marvell.c
@@ -194,6 +194,11 @@ static int marvell_read_page(struct phy_device *phydev)
 	return __phy_read(phydev, MII_MARVELL_PHY_PAGE);
 }
 
+static int marvell_get_page(struct phy_device *phydev)
+{
+	return phy_read(phydev, MII_MARVELL_PHY_PAGE);
+}
+
 static int marvell_write_page(struct phy_device *phydev, int page)
 {
 	return __phy_write(phydev, MII_MARVELL_PHY_PAGE, page);
@@ -1245,47 +1250,59 @@ static int marvell_read_status_page(struct phy_device *phydev, int page)
  * Some Marvell's phys have two modes: fiber and copper.
  * Both need status checked.
  * Description:
- *   First, check the fiber link and status.
- *   If the fiber link is down, check the copper link and status which
- *   will be the default value if both link are down.
+ *   First, check the link of the currently selected page. Unneeded page
+ *   switches should be prevented, they can trigger the ethernet driver to
+ *   register a link down event.
+ *   If the first checked link type is down, continue with checking the other
+ *   link type. This is needed for platforms that have a fiber and copper link
+ *   connected to the same phy.
  */
 static int marvell_read_status(struct phy_device *phydev)
 {
 	int err;
+	int page;
 
-	/* Check the fiber mode first */
 	if (linkmode_test_bit(ETHTOOL_LINK_MODE_FIBRE_BIT,
 			      phydev->supported) &&
 	    phydev->interface != PHY_INTERFACE_MODE_SGMII) {
-		err = marvell_set_page(phydev, MII_MARVELL_FIBER_PAGE);
-		if (err < 0)
-			goto error;
+		page = marvell_get_page(phydev);
+		if (page < 0)
+			return page;
+
+		if (page != MII_MARVELL_FIBER_PAGE &&
+		    page != MII_MARVELL_COPPER_PAGE) {
+			page = MII_MARVELL_FIBER_PAGE;
 
-		err = marvell_read_status_page(phydev, MII_MARVELL_FIBER_PAGE);
+			err = marvell_set_page(phydev, page);
+			if (err < 0)
+				return err;
+		}
+
+		err = marvell_read_status_page(phydev, page);
 		if (err < 0)
-			goto error;
+			return err;
 
-		/* If the fiber link is up, it is the selected and
-		 * used link. In this case, we need to stay in the
-		 * fiber page. Please to be careful about that, avoid
-		 * to restore Copper page in other functions which
-		 * could break the behaviour for some fiber phy like
+		/* If the link is up, it is the selected and
+		 * used link. In this case, we need to stay in that
+		 * page. Please to be careful about that, avoid
+		 * to restore the page in other functions which
+		 * could break the behaviour for some phy's like
 		 * 88E1512.
 		 */
 		if (phydev->link)
 			return 0;
 
-		/* If fiber link is down, check and save copper mode state */
-		err = marvell_set_page(phydev, MII_MARVELL_COPPER_PAGE);
+		page = (page == MII_MARVELL_FIBER_PAGE) ?
+			MII_MARVELL_COPPER_PAGE : MII_MARVELL_FIBER_PAGE;
+
+		err = marvell_set_page(phydev, page);
 		if (err < 0)
-			goto error;
+			return err;
+
+		return marvell_read_status_page(phydev, page);
 	}
 
 	return marvell_read_status_page(phydev, MII_MARVELL_COPPER_PAGE);
-
-error:
-	marvell_set_page(phydev, MII_MARVELL_COPPER_PAGE);
-	return err;
 }
 
 /* marvell_suspend
-- 
2.7.4