| Message ID | e6117cf857bea9af718d8c92d9d553c8f3a35e0a.1651574194.git.lukas@wunner.de (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | Polling be gone on LAN95xx | expand |
On Tue, May 03, 2022 at 03:15:04PM +0200, Lukas Wunner wrote: > When a PHY interrupt is signaled, the SMSC LAN95xx driver updates the > MAC full duplex mode and PHY flow control registers based on cached data > in struct phy_device: > > smsc95xx_status() # raises EVENT_LINK_RESET > usbnet_deferred_kevent() > smsc95xx_link_reset() # uses cached data in phydev > > Simultaneously, phylib polls link status once per second and updates > that cached data: > > phy_state_machine() > phy_check_link_status() > phy_read_status() > lan87xx_read_status() > genphy_read_status() # updates cached data in phydev > > If smsc95xx_link_reset() wins the race against genphy_read_status(), > the registers may be updated based on stale data. > > E.g. if the link was previously down, phydev->duplex is set to > DUPLEX_UNKNOWN and that's what smsc95xx_link_reset() will use, even > though genphy_read_status() may update it to DUPLEX_FULL afterwards. > > PHY interrupts are currently only enabled on suspend to trigger wakeup, > so the impact of the race is limited, but we're about to enable them > perpetually. > > Avoid the race by delaying execution of smsc95xx_link_reset() until > phy_state_machine() has done its job and calls back via > smsc95xx_handle_link_change(). > > Signaling EVENT_LINK_RESET on wakeup is not necessary because phylib > picks up link status changes through polling. So drop the declaration > of a ->link_reset() callback. > > Note that the semicolon on a line by itself added in smsc95xx_status() > is a placeholder for a function call which will be added in a subsequent > commit. That function call will actually handle the INT_ENP_PHY_INT_ > interrupt. > > Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> # LAN9514/9512/9500 > Tested-by: Ferry Toth <fntoth@gmail.com> # LAN9514 > Signed-off-by: Lukas Wunner <lukas@wunner.de> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Andrew
diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c index 6c37c7adde1b..6309ff8e75de 100644 --- a/drivers/net/usb/smsc95xx.c +++ b/drivers/net/usb/smsc95xx.c @@ -566,7 +566,7 @@ static int smsc95xx_phy_update_flowcontrol(struct usbnet *dev) return smsc95xx_write_reg(dev, AFC_CFG, afc_cfg); } -static int smsc95xx_link_reset(struct usbnet *dev) +static void smsc95xx_mac_update_fullduplex(struct usbnet *dev) { struct smsc95xx_priv *pdata = dev->driver_priv; unsigned long flags; @@ -583,14 +583,16 @@ static int smsc95xx_link_reset(struct usbnet *dev) spin_unlock_irqrestore(&pdata->mac_cr_lock, flags); ret = smsc95xx_write_reg(dev, MAC_CR, pdata->mac_cr); - if (ret < 0) - return ret; + if (ret < 0) { + if (ret != -ENODEV) + netdev_warn(dev->net, + "Error updating MAC full duplex mode\n"); + return; + } ret = smsc95xx_phy_update_flowcontrol(dev); if (ret < 0) netdev_warn(dev->net, "Error updating PHY flow control\n"); - - return ret; } static void smsc95xx_status(struct usbnet *dev, struct urb *urb) @@ -607,7 +609,7 @@ static void smsc95xx_status(struct usbnet *dev, struct urb *urb) netif_dbg(dev, link, dev->net, "intdata: 0x%08X\n", intdata); if (intdata & INT_ENP_PHY_INT_) - usbnet_defer_kevent(dev, EVENT_LINK_RESET); + ; else netdev_warn(dev->net, "unexpected interrupt, intdata=0x%08X\n", intdata); @@ -1070,6 +1072,7 @@ static void smsc95xx_handle_link_change(struct net_device *net) struct usbnet *dev = netdev_priv(net); phy_print_status(net->phydev); + smsc95xx_mac_update_fullduplex(dev); usbnet_defer_kevent(dev, EVENT_LINK_CHANGE); } @@ -1975,7 +1978,6 @@ static const struct driver_info smsc95xx_info = { .description = "smsc95xx USB 2.0 Ethernet", .bind = smsc95xx_bind, .unbind = smsc95xx_unbind, - .link_reset = smsc95xx_link_reset, .reset = smsc95xx_reset, .check_connect = smsc95xx_start_phy, .stop = smsc95xx_stop,
When a PHY interrupt is signaled, the SMSC LAN95xx driver updates the MAC full duplex mode and PHY flow control registers based on cached data in struct phy_device: smsc95xx_status() # raises EVENT_LINK_RESET usbnet_deferred_kevent() smsc95xx_link_reset() # uses cached data in phydev Simultaneously, phylib polls link status once per second and updates that cached data: phy_state_machine() phy_check_link_status() phy_read_status() lan87xx_read_status() genphy_read_status() # updates cached data in phydev If smsc95xx_link_reset() wins the race against genphy_read_status(), the registers may be updated based on stale data. E.g. if the link was previously down, phydev->duplex is set to DUPLEX_UNKNOWN and that's what smsc95xx_link_reset() will use, even though genphy_read_status() may update it to DUPLEX_FULL afterwards. PHY interrupts are currently only enabled on suspend to trigger wakeup, so the impact of the race is limited, but we're about to enable them perpetually. Avoid the race by delaying execution of smsc95xx_link_reset() until phy_state_machine() has done its job and calls back via smsc95xx_handle_link_change(). Signaling EVENT_LINK_RESET on wakeup is not necessary because phylib picks up link status changes through polling. So drop the declaration of a ->link_reset() callback. Note that the semicolon on a line by itself added in smsc95xx_status() is a placeholder for a function call which will be added in a subsequent commit. That function call will actually handle the INT_ENP_PHY_INT_ interrupt. Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> # LAN9514/9512/9500 Tested-by: Ferry Toth <fntoth@gmail.com> # LAN9514 Signed-off-by: Lukas Wunner <lukas@wunner.de> --- Changes since v1: * Silence "Error updating MAC full duplex mode" warning if it's caused by hot-removal. (Oleksij Rempel) * Explain in commit message why a semicolon on a line by itself is temporarily added in smsc95xx_status(). (Andrew Lunn) drivers/net/usb/smsc95xx.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)