net: sfp: re-attempt probing for phy

Some 1000BASE-T PHY modules take a while for the PHY to wake up.
Retry the probe a number of times before deciding that the module has
no PHY.

Tested with:
 Sourcephotonics SPGBTXCNFC - PHY takes less than 50ms to respond.
 Champion One 1000SFPT - PHY takes about 200ms to respond.
 Mikrotik S-RJ01 - no PHY
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/sfp.c

@@ -62,6 +62,7 @@ enum {
 	SFP_S_FAIL,
 	SFP_S_WAIT,
 	SFP_S_INIT,
+	SFP_S_INIT_PHY,
 	SFP_S_INIT_TX_FAULT,
 	SFP_S_WAIT_LOS,
 	SFP_S_LINK_UP,
@@ -126,6 +127,7 @@ static const char * const sm_state_strings[] = {
 	[SFP_S_FAIL] = "fail",
 	[SFP_S_WAIT] = "wait",
 	[SFP_S_INIT] = "init",
+	[SFP_S_INIT_PHY] = "init_phy",
 	[SFP_S_INIT_TX_FAULT] = "init_tx_fault",
 	[SFP_S_WAIT_LOS] = "wait_los",
 	[SFP_S_LINK_UP] = "link_up",
@@ -180,6 +182,12 @@ static const enum gpiod_flags gpio_flags[] = {
 #define N_FAULT_INIT		5
 #define N_FAULT			5
 
+/* T_PHY_RETRY is the time interval between attempts to probe the PHY.
+ * R_PHY_RETRY is the number of attempts.
+ */
+#define T_PHY_RETRY		msecs_to_jiffies(50)
+#define R_PHY_RETRY		12
+
 /* SFP module presence detection is poor: the three MOD DEF signals are
  * the same length on the PCB, which means it's possible for MOD DEF 0 to
  * connect before the I2C bus on MOD DEF 1/2.
@@ -235,6 +243,7 @@ struct sfp {
 	unsigned char sm_dev_state;
 	unsigned short sm_state;
 	unsigned char sm_fault_retries;
+	unsigned char sm_phy_retries;
 
 	struct sfp_eeprom_id id;
 	unsigned int module_power_mW;
@@ -1416,10 +1425,8 @@ static int sfp_sm_probe_phy(struct sfp *sfp, bool is_c45)
 	int err;
 
 	phy = get_phy_device(sfp->i2c_mii, SFP_PHY_ADDR, is_c45);
-	if (phy == ERR_PTR(-ENODEV)) {
-		dev_info(sfp->dev, "no PHY detected\n");
-		return 0;
-	}
+	if (phy == ERR_PTR(-ENODEV))
+		return PTR_ERR(phy);
 	if (IS_ERR(phy)) {
 		dev_err(sfp->dev, "mdiobus scan returned %ld\n", PTR_ERR(phy));
 		return PTR_ERR(phy);
@@ -1867,6 +1874,7 @@ static void sfp_sm_module(struct sfp *sfp, unsigned int event)
 static void sfp_sm_main(struct sfp *sfp, unsigned int event)
 {
 	unsigned long timeout;
+	int ret;
 
 	/* Some events are global */
 	if (sfp->sm_state != SFP_S_DOWN &&
@@ -1940,10 +1948,28 @@ static void sfp_sm_main(struct sfp *sfp, unsigned int event)
 			sfp_sm_fault(sfp, SFP_S_INIT_TX_FAULT,
 				     sfp->sm_fault_retries == N_FAULT_INIT);
 		} else if (event == SFP_E_TIMEOUT || event == SFP_E_TX_CLEAR) {
-	init_done:	/* TX_FAULT deasserted or we timed out with TX_FAULT
+	init_done:
+			sfp->sm_phy_retries = R_PHY_RETRY;
+			goto phy_probe;
+		}
+		break;
+
+	case SFP_S_INIT_PHY:
+		if (event != SFP_E_TIMEOUT)
+			break;
+	phy_probe:
+		/* TX_FAULT deasserted or we timed out with TX_FAULT
 		 * clear.  Probe for the PHY and check the LOS state.
 		 */
-			if (sfp_sm_probe_for_phy(sfp)) {
+		ret = sfp_sm_probe_for_phy(sfp);
+		if (ret == -ENODEV) {
+			if (--sfp->sm_phy_retries) {
+				sfp_sm_next(sfp, SFP_S_INIT_PHY, T_PHY_RETRY);
+				break;
+			} else {
+				dev_info(sfp->dev, "no PHY detected\n");
+			}
+		} else if (ret) {
 			sfp_sm_next(sfp, SFP_S_FAIL, 0);
 			break;
 		}
@@ -1955,7 +1981,6 @@ static void sfp_sm_main(struct sfp *sfp, unsigned int event)
 
 		/* Reset the fault retry count */
 		sfp->sm_fault_retries = N_FAULT;
-		}
 		break;
 
 	case SFP_S_INIT_TX_FAULT: