[PATCH net-next] net: phy: realtek: make sure paged read is protected by mutex

[Daniel Golle]

As we cannot rely on phy_read_paged function before the PHY is
identified, the paged read in rtlgen_supports_2_5gbps needs to be open
coded as it is being called by the match_phy_device function, ie. before
.read_page and .write_page have been populated.

Make sure it is also protected by the MDIO bus mutex and use
rtl821x_write_page instead of 3 individually locked MDIO bus operations.

Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx>
---
 drivers/net/phy/realtek.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index 3941cfa1c5f2..c4d0d93523ad 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -1030,9 +1030,11 @@ static bool rtlgen_supports_2_5gbps(struct phy_device *phydev)
 {
 	int val;
 
-	phy_write(phydev, RTL821x_PAGE_SELECT, 0xa61);
-	val = phy_read(phydev, 0x13);
-	phy_write(phydev, RTL821x_PAGE_SELECT, 0);
+	mutex_lock(&phydev->mdio.bus->mdio_lock);
+	rtl821x_write_page(phydev, 0xa61);
+	val = __phy_read(phydev, 0x13);
+	rtl821x_write_page(phydev, 0);
+	mutex_unlock(&phydev->mdio.bus->mdio_lock);
 
 	return val >= 0 && val & MDIO_PMA_SPEED_2_5G;
 }
-- 
2.46.2