net: phy: marvell: Configure TDR pulse based on measurement length

When performing a TDR measurement for a short distance, the pulse
width should be low, to help differentiate between the outgoing pulse
and any reflection. For longer distances, the pulse should be wider,
to help with attenuation.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/marvell.c

@@ -214,6 +214,11 @@
 #define MII_VCT5_TX_PULSE_CTRL_MAX_AMP			BIT(7)
 #define MII_VCT5_TX_PULSE_CTRL_GT_140m_46_86mV		(0x6 << 0)
 
+/* For TDR measurements less than 11 meters, a short pulse should be
+ * used.
+ */
+#define TDR_SHORT_CABLE_LENGTH	11
+
 #define MII_VCT7_PAIR_0_DISTANCE	0x10
 #define MII_VCT7_PAIR_1_DISTANCE	0x11
 #define MII_VCT7_PAIR_2_DISTANCE	0x12
@@ -1835,14 +1840,19 @@ static int marvell_vct5_amplitude_graph(struct phy_device *phydev)
 {
 	struct marvell_priv *priv = phydev->priv;
 	int distance;
+	u16 width;
 	int page;
 	int err;
 	u16 reg;
 
+	if (priv->first <= TDR_SHORT_CABLE_LENGTH)
+		width = MII_VCT5_TX_PULSE_CTRL_PULSE_WIDTH_32nS;
+	else
+		width = MII_VCT5_TX_PULSE_CTRL_PULSE_WIDTH_128nS;
+
 	reg = MII_VCT5_TX_PULSE_CTRL_GT_140m_46_86mV |
 		MII_VCT5_TX_PULSE_CTRL_DONT_WAIT_LINK_DOWN |
-		MII_VCT5_TX_PULSE_CTRL_MAX_AMP |
-		MII_VCT5_TX_PULSE_CTRL_PULSE_WIDTH_32nS;
+		MII_VCT5_TX_PULSE_CTRL_MAX_AMP | width;
 
 	err = phy_write_paged(phydev, MII_MARVELL_VCT5_PAGE,
 			      MII_VCT5_TX_PULSE_CTRL, reg);
@@ -1866,6 +1876,17 @@ static int marvell_vct5_amplitude_graph(struct phy_device *phydev)
 						      priv->pair);
 		if (err)
 			goto restore_page;
+
+		if (distance > TDR_SHORT_CABLE_LENGTH &&
+		    width == MII_VCT5_TX_PULSE_CTRL_PULSE_WIDTH_32nS) {
+			width = MII_VCT5_TX_PULSE_CTRL_PULSE_WIDTH_128nS;
+			reg = MII_VCT5_TX_PULSE_CTRL_GT_140m_46_86mV |
+				MII_VCT5_TX_PULSE_CTRL_DONT_WAIT_LINK_DOWN |
+				MII_VCT5_TX_PULSE_CTRL_MAX_AMP | width;
+			err = __phy_write(phydev, MII_VCT5_TX_PULSE_CTRL, reg);
+			if (err)
+				goto restore_page;
+		}
 	}
 
 restore_page: