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Subject[PATCH v2] net: smsc911x: Quieten netif during suspend
Date
If the network interface is kept running during suspend, the net core
may call net_device_ops.ndo_start_xmit() while the Ethernet device is
still suspended, which may lead to a system crash.

E.g. on sh73a0/kzm9g and r8a73a4/ape6evm, the external Ethernet chip is
driven by a PM controlled clock. If the Ethernet registers are accessed
while the clock is not running, the system will crash with an imprecise
external abort.

As this is a race condition with a small time window, it is not so easy
to trigger at will. Using pm_test may increase your chances:

# echo 0 > /sys/module/printk/parameters/console_suspend
# echo platform > /sys/power/pm_test
# echo mem > /sys/power/state

To fix this, make sure the network interface is quietened during
suspend.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is v2 of the series "[PATCH 0/2] net: Fix crashes due to activity
during suspend", which degenerated into a single patch after commit
ebc8254aeae34226 ("Revert "net: phy: Correctly process PHY_HALTED in
phy_stop_machine()"") made "[PATCH 1/2] net: phy: Freeze PHY polling before
suspending devices" no longer needed.

v2:
- Spelling s/quit/quiet/g.

No stacktrace is provided, as the imprecise external abort is usually
reported from an innocent looking and unrelated function like
__loop_delay(), cpu_idle_poll(), or arch_timer_read_counter_long().
---
drivers/net/ethernet/smsc/smsc911x.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/smsc/smsc911x.c b/drivers/net/ethernet/smsc/smsc911x.c
index 0b6a39b003a4e188..012fb66eed8dd618 100644
--- a/drivers/net/ethernet/smsc/smsc911x.c
+++ b/drivers/net/ethernet/smsc/smsc911x.c
@@ -2595,6 +2595,11 @@ static int smsc911x_suspend(struct device *dev)
struct net_device *ndev = dev_get_drvdata(dev);
struct smsc911x_data *pdata = netdev_priv(ndev);

+ if (netif_running(ndev)) {
+ netif_stop_queue(ndev);
+ netif_device_detach(ndev);
+ }
+
/* enable wake on LAN, energy detection and the external PME
* signal. */
smsc911x_reg_write(pdata, PMT_CTRL,
@@ -2628,7 +2633,15 @@ static int smsc911x_resume(struct device *dev)
while (!(smsc911x_reg_read(pdata, PMT_CTRL) & PMT_CTRL_READY_) && --to)
udelay(1000);

- return (to == 0) ? -EIO : 0;
+ if (to == 0)
+ return -EIO;
+
+ if (netif_running(ndev)) {
+ netif_device_attach(ndev);
+ netif_start_queue(ndev);
+ }
+
+ return 0;
}

static const struct dev_pm_ops smsc911x_pm_ops = {
--
2.7.4
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