Fix an issue where the kernel would stall during netboot, showing the "sched: RT throttling activated" message. This stall was triggered by the behavior of the mii_interrupt bit (Bit 7 - DP83TD510E_STS_MII_INT) in the DP83TD510E's PHY_STS Register (Address = 0x10). The DP83TD510E datasheet (2020) states that the bit clears on write, however, in practice, the bit clears on read.

This discrepancy had significant implications on the driver's interrupt handling. The PHY_STS Register was used by handle_interrupt() to check for pending interrupts and by read_status() to get the current link status. The call to read_status() was unintentionally clearing the mii_interrupt status bit without deasserting the IRQ pin, causing handle_interrupt() to miss other pending interrupts. This issue was most apparent during netboot.

The fix refrains from using the PHY_STS Register for interrupt handling. Instead, we now solely rely on the INTERRUPT_REG_1 Register (Address = 0x12) and INTERRUPT_REG_2 Register (Address = 0x13) for this purpose. These registers directly influence the IRQ pin state and are latched high until read.

Note: The INTERRUPT_REG_2 Register (Address = 0x13) exists and can also be used for interrupt handling, specifically for "Aneg page received interrupt" and "Polarity change interrupt". However, these features are currently not supported by this driver.

Fixes: 165cd04fe253 ("net: phy: dp83td510: Add support for the DP83TD510 Ethernet PHY") Cc: stable@vger.kernel.org Signed-off-by: Oleksij Rempel o.rempel@pengutronix.de Reviewed-by: Andrew Lunn andrew@lunn.ch --- drivers/net/phy/dp83td510.c | 23 +++++------------------ 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/drivers/net/phy/dp83td510.c b/drivers/net/phy/dp83td510.c index 3cd9a77f9532..d7616b13c594 100644 --- a/drivers/net/phy/dp83td510.c +++ b/drivers/net/phy/dp83td510.c @@ -12,6 +12,11 @@

/* MDIO_MMD_VEND2 registers */ #define DP83TD510E_PHY_STS 0x10 +/* Bit 7 - mii_interrupt, active high. Clears on read. + * Note: Clearing does not necessarily deactivate IRQ pin if interrupts pending. + * This differs from the DP83TD510E datasheet (2020) which states this bit + * clears on write 0. + */ #define DP83TD510E_STS_MII_INT BIT(7) #define DP83TD510E_LINK_STATUS BIT(0)

@@ -53,12 +58,6 @@ static int dp83td510_config_intr(struct phy_device *phydev) int ret;

if (phydev->interrupts == PHY_INTERRUPT_ENABLED) { - /* Clear any pending interrupts */ - ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PHY_STS, - 0x0); - if (ret) - return ret; - ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_INTERRUPT_REG_1, DP83TD510E_INT1_LINK_EN); @@ -81,10 +80,6 @@ static int dp83td510_config_intr(struct phy_device *phydev) DP83TD510E_GENCFG_INT_EN); if (ret) return ret; - - /* Clear any pending interrupts */ - ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PHY_STS, - 0x0); }

return ret; @@ -94,14 +89,6 @@ static irqreturn_t dp83td510_handle_interrupt(struct phy_device *phydev) { int ret;

- ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_PHY_STS); - if (ret < 0) { - phy_error(phydev); - return IRQ_NONE; - } else if (!(ret & DP83TD510E_STS_MII_INT)) { - return IRQ_NONE; - } - /* Read the current enabled interrupts */ ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TD510E_INTERRUPT_REG_1); if (ret < 0) {