sfp: improve RX_LOS handling

There are two bits in the option word for the RX_LOS signal.  One
reports that the RX_LOS signal is active high, the other reports that
it is active low.  When both or neither are set, the result is not
well defined in the specification.

Rather than assuming that neither set means normal RX_LOS, take this
as meaning no RX_LOS signal available, thereby ignoring the signal.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/sfp.c

@@ -351,12 +351,13 @@ static void sfp_sm_link_check_los(struct sfp *sfp)
 {
 	unsigned int los = sfp->state & SFP_F_LOS;
 
-	/* FIXME: what if neither SFP_OPTIONS_LOS_INVERTED nor
-	 * SFP_OPTIONS_LOS_NORMAL are set?  For now, we assume
-	 * the same as SFP_OPTIONS_LOS_NORMAL set.
+	/* If neither SFP_OPTIONS_LOS_INVERTED nor SFP_OPTIONS_LOS_NORMAL
+	 * are set, we assume that no LOS signal is available.
 	 */
 	if (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_LOS_INVERTED))
 		los ^= SFP_F_LOS;
+	else if (!(sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_LOS_NORMAL)))
+		los = 0;
 
 	if (los)
 		sfp_sm_next(sfp, SFP_S_WAIT_LOS, 0);
@@ -364,6 +365,22 @@ static void sfp_sm_link_check_los(struct sfp *sfp)
 		sfp_sm_link_up(sfp);
 }
 
+static bool sfp_los_event_active(struct sfp *sfp, unsigned int event)
+{
+	return (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_LOS_INVERTED) &&
+		event == SFP_E_LOS_LOW) ||
+	       (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_LOS_NORMAL) &&
+		event == SFP_E_LOS_HIGH);
+}
+
+static bool sfp_los_event_inactive(struct sfp *sfp, unsigned int event)
+{
+	return (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_LOS_INVERTED) &&
+		event == SFP_E_LOS_HIGH) ||
+	       (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_LOS_NORMAL) &&
+		event == SFP_E_LOS_LOW);
+}
+
 static void sfp_sm_fault(struct sfp *sfp, bool warn)
 {
 	if (sfp->sm_retries && !--sfp->sm_retries) {
@@ -581,10 +598,7 @@ static void sfp_sm_event(struct sfp *sfp, unsigned int event)
 	case SFP_S_WAIT_LOS:
 		if (event == SFP_E_TX_FAULT)
 			sfp_sm_fault(sfp, true);
-		else if (event ==
-			 (sfp->id.ext.options &
-			  cpu_to_be16(SFP_OPTIONS_LOS_INVERTED) ?
-			  SFP_E_LOS_HIGH : SFP_E_LOS_LOW))
+		else if (sfp_los_event_inactive(sfp, event))
 			sfp_sm_link_up(sfp);
 		break;
 
@@ -592,10 +606,7 @@ static void sfp_sm_event(struct sfp *sfp, unsigned int event)
 		if (event == SFP_E_TX_FAULT) {
 			sfp_sm_link_down(sfp);
 			sfp_sm_fault(sfp, true);
-		} else if (event ==
-			   (sfp->id.ext.options &
-			    cpu_to_be16(SFP_OPTIONS_LOS_INVERTED) ?
-			    SFP_E_LOS_LOW : SFP_E_LOS_HIGH)) {
+		} else if (sfp_los_event_active(sfp, event)) {
 			sfp_sm_link_down(sfp);
 			sfp_sm_next(sfp, SFP_S_WAIT_LOS, 0);
 		}