[PATCH net-next v8 09/11] net: phy: ncn26000: Support for loopback

[Selvamani Rajagopal via B4 Relay <devnull+Selvamani.Rajagopal.onsemi.com@kernel.org>]

From: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

Adding loopback support for S2500 internal PHY to help running
loopback test through ethtool.

This instance requires only manipulating the loopback bit in
the PHY only. So, added a generic helper function to modify
loopback bit of the PHY without modifying any other bit. This
will help the PHYs that may have fixed speed, like 10Base-T1S
or PHYs that don't need any other settings to set them in
loopback mode.

Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

---
changes in v8
  - No code change. Changes were in two different patches.
    Merged into one.
changes in v7
  - No change
changes in v6
  - No change
changes in v5
  - No change
changes in v4
  - Moved the onsemi implementation to a new, genphy API to
    make it vendor agnostic.
changes in v3
  - Addd loopback functionality for onsemi's PHY driver
  - First patch
---
 drivers/net/phy/dp83867.c    | 11 +----------
 drivers/net/phy/ncn26000.c   |  1 +
 drivers/net/phy/phy_device.c | 20 ++++++++++++++++++++
 include/linux/phy.h          |  2 ++
 4 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c
index a3cd5cb11ea0..38c17a68cf26 100644
--- a/drivers/net/phy/dp83867.c
+++ b/drivers/net/phy/dp83867.c
@@ -1058,15 +1058,6 @@ static void dp83867_link_change_notify(struct phy_device *phydev)
 	}
 }
 
-static int dp83867_loopback(struct phy_device *phydev, bool enable, int speed)
-{
-	if (enable && speed)
-		return -EOPNOTSUPP;
-
-	return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
-			  enable ? BMCR_LOOPBACK : 0);
-}
-
 static int
 dp83867_led_brightness_set(struct phy_device *phydev,
 			   u8 index, enum led_brightness brightness)
@@ -1292,7 +1283,7 @@ static struct phy_driver dp83867_driver[] = {
 		.resume		= dp83867_resume,
 
 		.link_change_notify = dp83867_link_change_notify,
-		.set_loopback	= dp83867_loopback,
+		.set_loopback	= genphy_loopback_fixed_speed,
 
 		.led_brightness_set = dp83867_led_brightness_set,
 		.led_hw_is_supported = dp83867_led_hw_is_supported,
diff --git a/drivers/net/phy/ncn26000.c b/drivers/net/phy/ncn26000.c
index b362e85c7911..933cba6d00b5 100644
--- a/drivers/net/phy/ncn26000.c
+++ b/drivers/net/phy/ncn26000.c
@@ -178,6 +178,7 @@ static struct phy_driver ncn26000_driver[] = {
 		.config_aneg           = ncn26000_config_aneg,
 		.read_status           = ncn26000_read_status,
 		.handle_interrupt      = ncn26000_handle_interrupt,
+		.set_loopback          = genphy_loopback_fixed_speed,
 		.set_plca_cfg          = ncn26000_c45_plca_set_cfg,
 		.get_plca_cfg          = genphy_c45_plca_get_cfg,
 		.get_plca_status       = genphy_c45_plca_get_status,
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 5b13a74e2fa9..ca438d4e8fcb 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2775,6 +2775,26 @@ int genphy_write_mmd_unsupported(struct phy_device *phdev, int devnum,
 }
 EXPORT_SYMBOL(genphy_write_mmd_unsupported);
 
+/**
+ * genphy_loopback_fixed_speed - Helper to modify the PHY loopback mode
+ * without affecting any other settings.
+ * @phydev: The phy_device struct
+ * @enable: Flag to enable or disable the PHY level loopback.
+ * @speed: Speed setting. Not expected to be set. Error if it is set.
+ *
+ * Returns: 0 if successful, negative error code on failure.
+ */
+int genphy_loopback_fixed_speed(struct phy_device *phydev, bool enable,
+				int speed)
+{
+	if (enable && speed)
+		return -EOPNOTSUPP;
+
+	return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
+			  enable ? BMCR_LOOPBACK : 0);
+}
+EXPORT_SYMBOL(genphy_loopback_fixed_speed);
+
 int genphy_suspend(struct phy_device *phydev)
 {
 	return phy_set_bits(phydev, MII_BMCR, BMCR_PDOWN);
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 7c5098a0dd6c..c1b9bc305c82 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -2327,6 +2327,8 @@ int genphy_read_mmd_unsupported(struct phy_device *phdev, int devad,
 				u16 regnum);
 int genphy_write_mmd_unsupported(struct phy_device *phdev, int devnum,
 				 u16 regnum, u16 val);
+int genphy_loopback_fixed_speed(struct phy_device *phydev, bool enable,
+				int speed);
 
 /* Clause 37 */
 int genphy_c37_config_aneg(struct phy_device *phydev);

-- 
2.43.0