net/smsc911x: Fix delays in the PHY enable/disable routines

Increased delay in the smsc911x_phy_disable_energy_detect (from 1ms to 2ms).
Dropped delays in the smsc911x_phy_enable_energy_detect (100ms and 1ms).

The patch affect SMSC LAN generation 4 chips with integrated PHY (LAN9221).

I saw problems with soft reset due to wrong udelay timings.
After I fixed udelay, I measured the time needed to bring integrated PHY
from power-down to operational mode (the time beetween clearing EDPWRDOWN
bit and soft reset complete event). I got 1ms (measured using ktime_get).
The value is equal to the current value (1ms) used in the
smsc911x_phy_disable_energy_detect. It is near the upper bound and in order
to avoid rare soft reset faults it is doubled (2ms).

I don't know official timing for bringing up integrated PHY as specs doesn't
clarify this (or may be I didn't found).

It looks safe to drop delays before and after setting EDPWRDOWN bit
(enable PHY power-down mode). I didn't saw any regressions with the patch.

The patch was reviewed by Steve Glendinning and Microchip Team.

Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>
Acked-by: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 5 deletions

diff --git a/drivers/net/ethernet/smsc/smsc911x.c b/drivers/net/ethernet/smsc/smsc911x.c
index 1e1f6194cb37..c3bf17f89b05 100644
--- a/drivers/net/ethernet/smsc/smsc911x.c
+++ b/drivers/net/ethernet/smsc/smsc911x.c
@@ -1366,8 +1366,8 @@ static int smsc911x_phy_disable_energy_detect(struct smsc911x_data *pdata)
                         SMSC_WARN(pdata, drv, "Failed writing PHY control reg");
                         return rc;
                 }
-
-                mdelay(1);
+                /* Allow PHY to wakeup */
+                mdelay(2);
         }
 
         return 0;
@@ -1389,7 +1389,6 @@ static int smsc911x_phy_enable_energy_detect(struct smsc911x_data *pdata)
 
         /* Only enable if energy detect mode is already disabled */
         if (!(rc & MII_LAN83C185_EDPWRDOWN)) {
-                mdelay(100);
                 /* Enable energy detect mode for this SMSC Transceivers */
                 rc = phy_write(pdata->phy_dev, MII_LAN83C185_CTRL_STATUS,
                                rc | MII_LAN83C185_EDPWRDOWN);
@@ -1398,8 +1397,6 @@ static int smsc911x_phy_enable_energy_detect(struct smsc911x_data *pdata)
                         SMSC_WARN(pdata, drv, "Failed writing PHY control reg");
                         return rc;
                 }
-
-                mdelay(1);
         }
         return 0;
 }