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ramips: mt7530 swconfig: fix race condition in register access 

The mt7530_{r,w}32 operation over MDIO uses 3 mdiobus operations and
does not hold a lock, which causes a race condition when multiple
threads try to access a register, they may get unexpected results.

To avoid this, handle the MDIO lock manually, and use the unlocked
__mdiobus_{read,write} in the critical section.

This fixes the "Ghost VLAN" artifact[1] in MT7530/7621 when the VLAN
operation and the swconfig LED link status poll race between each other.

[1] https://forum.openwrt.org/t/mysterious-vlan-ids-on-mt7621-device/64495

Signed-off-by: DENG Qingfang <dqfext@gmail.com>
(cherry picked from commit f99c9cd9c4)
This commit is contained in:
DENG Qingfang 2021-04-03 22:59:15 +08:00 committed by Hauke Mehrtens
parent cc6ad94fb9
commit 6552f31acd
1 changed files with 10 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
target/linux/ramips/files/drivers/net/ethernet/ralink/mt7530.c
View File

@ -290,9 +290,11 @@ mt7530_r32(struct mt7530_priv *priv, u32 reg)
if (priv->bus) {
u16 high, low;
mdiobus_write(priv->bus, 0x1f, 0x1f, (reg >> 6) & 0x3ff);
low = mdiobus_read(priv->bus, 0x1f, (reg >> 2) & 0xf);
high = mdiobus_read(priv->bus, 0x1f, 0x10);
mutex_lock(&priv->bus->mdio_lock);
__mdiobus_write(priv->bus, 0x1f, 0x1f, (reg >> 6) & 0x3ff);
low = __mdiobus_read(priv->bus, 0x1f, (reg >> 2) & 0xf);
high = __mdiobus_read(priv->bus, 0x1f, 0x10);
mutex_unlock(&priv->bus->mdio_lock);
return (high << 16) | (low & 0xffff);
}
@ -307,9 +309,11 @@ static void
mt7530_w32(struct mt7530_priv *priv, u32 reg, u32 val)
{
if (priv->bus) {
mdiobus_write(priv->bus, 0x1f, 0x1f, (reg >> 6) & 0x3ff);
mdiobus_write(priv->bus, 0x1f, (reg >> 2) & 0xf, val & 0xffff);
mdiobus_write(priv->bus, 0x1f, 0x10, val >> 16);
mutex_lock(&priv->bus->mdio_lock);
__mdiobus_write(priv->bus, 0x1f, 0x1f, (reg >> 6) & 0x3ff);
__mdiobus_write(priv->bus, 0x1f, (reg >> 2) & 0xf, val & 0xffff);
__mdiobus_write(priv->bus, 0x1f, 0x10, val >> 16);
mutex_unlock(&priv->bus->mdio_lock);
return;
}