net: phy: mscc: fix deadlock in vsc85xx_default_config

The vsc85xx_default_config function called in the vsc85xx_config_init function which is used by VSC8530, VSC8531, VSC8540 and VSC8541 PHYs mistakenly calls phy_read and phy_write in-between phy_select_page and phy_restore_page.

phy_select_page and phy_restore_page actually take and release the MDIO bus lock and phy_write and phy_read take and release the lock to write or read to a PHY register.

Let's fix this deadlock by using phy_modify_paged which handles correctly a read followed by a write in a non-standard page.

Fixes 6a0bfbbe20b0 ("net: phy: mscc: migrate to phy_select/restore_page functions")

Signed-off-by Quentin Schulz <[email protected]>

---

v2:
- use phy_modify_paged instead of
phy_select_page -> __phy_read -> __phy_write -> phy_restore_page

 drivers/net/phy/mscc.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

drivers/net/phy/mscc.c +0 -0

index 62269e578718..4dcf7ad06259 100644
@@ -810,17 +810,16 @@ static int vsc85xx_default_config(struct phy_device *phydev)
 
 	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;

drivers/net/phy/mscc.c +0 -6

-	reg_val = phy_read(phydev, MSCC_PHY_RGMII_CNTL);
-	reg_val &= ~(RGMII_RX_CLK_DELAY_MASK);
-	reg_val |= (RGMII_RX_CLK_DELAY_1_1_NS << RGMII_RX_CLK_DELAY_POS);
-	phy_write(phydev, MSCC_PHY_RGMII_CNTL, reg_val);
-
 out_unlock:
-	rc = phy_restore_page(phydev, rc, rc > 0 ? 0 : rc);
 	mutex_unlock(&phydev->lock);
 
 	return rc;

Signature · 1 line

2.17.1

Quoted 31 lines · Quentin Schulz

The vsc85xx_default_config function called in the vsc85xx_config_init function which is used by VSC8530, VSC8531, VSC8540 and VSC8541 PHYs mistakenly calls phy_read and phy_write in-between phy_select_page and phy_restore_page.

phy_select_page and phy_restore_page actually take and release the MDIO bus lock and phy_write and phy_read take and release the lock to write or read to a PHY register.

Let's fix this deadlock by using phy_modify_paged which handles correctly a read followed by a write in a non-standard page.

Fixes 6a0bfbbe20b0 ("net: phy: mscc: migrate to phy_select/restore_page functions")

Signed-off-by Quentin Schulz <[email protected]>

---

v2:
- use phy_modify_paged instead of
phy_select_page -> __phy_read -> __phy_write -> phy_restore_page

 drivers/net/phy/mscc.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

drivers/net/phy/mscc.c +0 -0

index 62269e578718..4dcf7ad06259 100644
@@ -810,17 +810,16 @@ static int vsc85xx_default_config(struct phy_device *phydev)
 
 	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;

drivers/net/phy/mscc.c static int vsc85xx_default_config(struct phy_device *phydev) · line 820

Quoted 10 lines

drivers/net/phy/mscc.c +6 -1

 	mutex_lock(&phydev->lock);
-	rc = phy_select_page(phydev, MSCC_PHY_PAGE_EXTENDED_2);
+
+	reg_val = RGMII_RX_CLK_DELAY_1_1_NS << RGMII_RX_CLK_DELAY_POS;
+
+	rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_2,
+			      MSCC_PHY_RGMII_CNTL, RGMII_RX_CLK_DELAY_MASK,
+			      reg_val);
 	if (rc < 0)
 		goto out_unlock;

Hi Quentin

Isn't this goto now pointless. You are not jumping over anything.