r8152: fix the poor throughput for 2.5G devices

Fix the poor throughput for 2.5G devices, when changing the speed from
auto mode to force mode. This patch is used to notify the MAC when the
mode is changed.

Fixes: 195aae32 ("r8152: support new chips")
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/r8152.c

@@ -199,6 +199,7 @@
 #define OCP_EEE_AR		0xa41a
 #define OCP_EEE_DATA		0xa41c
 #define OCP_PHY_STATUS		0xa420
+#define OCP_INTR_EN		0xa424
 #define OCP_NCTL_CFG		0xa42c
 #define OCP_POWER_CFG		0xa430
 #define OCP_EEE_CFG		0xa432
@@ -620,6 +621,9 @@ enum spd_duplex {
 #define PHY_STAT_LAN_ON		3
 #define PHY_STAT_PWRDN		5
 
+/* OCP_INTR_EN */
+#define INTR_SPEED_FORCE	BIT(3)
+
 /* OCP_NCTL_CFG */
 #define PGA_RETURN_EN		BIT(1)
 
@@ -7554,6 +7558,11 @@ static void r8156_hw_phy_cfg(struct r8152 *tp)
 				      ((swap_a & 0x1f) << 8) |
 				      ((swap_a >> 8) & 0x1f));
 		}
+
+		/* Notify the MAC when the speed is changed to force mode. */
+		data = ocp_reg_read(tp, OCP_INTR_EN);
+		data |= INTR_SPEED_FORCE;
+		ocp_reg_write(tp, OCP_INTR_EN, data);
 		break;
 	default:
 		break;
@@ -7949,6 +7958,11 @@ static void r8156b_hw_phy_cfg(struct r8152 *tp)
 		break;
 	}
 
+	/* Notify the MAC when the speed is changed to force mode. */
+	data = ocp_reg_read(tp, OCP_INTR_EN);
+	data |= INTR_SPEED_FORCE;
+	ocp_reg_write(tp, OCP_INTR_EN, data);
+
 	if (rtl_phy_patch_request(tp, true, true))
 		return;