[PATCH] Fix genphy_restart_aneg() for Micrel's ksz9031.

[Guillermo Rodriguez Garcia]

From: grodriguez <guille.rodriguez at gmail.com>

Commit da89ee8f2e04 ("Center FLP timing at 16ms") breaks
genphy_restart_aneg() for Micrel's ksz9031. According to the
datasheet, the ksz9031 requires a wait of 1ms after clearing
the PDOWN bit and before read/write access to any PHY registers.
---
 drivers/net/phy/phy.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 73176fb..ed69d9b 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -561,7 +561,7 @@ int phy_wait_aneg_done(struct phy_device *phydev)
  */
 int genphy_restart_aneg(struct phy_device *phydev)
 {
-	int ctl;
+	int ctl, pdown;
 
 	ctl = phy_read(phydev, MII_BMCR);
 
@@ -574,6 +574,7 @@ int genphy_restart_aneg(struct phy_device *phydev)
 	ctl &= ~(BMCR_ISOLATE);
 
 	/* Clear powerdown bit which eventually is set on some phys */
+	pdown = ctl & BMCR_PDOWN;
 	ctl &= ~BMCR_PDOWN;
 
 	ctl = phy_write(phydev, MII_BMCR, ctl);
@@ -581,6 +582,12 @@ int genphy_restart_aneg(struct phy_device *phydev)
 	if (ctl < 0)
 		return ctl;
 
+	/* Micrel's ksz9031 (and perhaps others?): Changing the PDOWN bit
+	 * from '1' to '0' generates an internal reset. Must wait a minimum
+	 * of 1ms before read/write access to the PHY registers. */
+	if (pdown)
+		mdelay(1);
+
 	return 0;
 }
 
-- 
1.7.9.5