From: Linus Lüssing ll@simonwunderlich.de
[ Upstream commit 4925642d541278575ad1948c5924d71ffd57ef14 ]
In tests with two Lima boards from 8devices (QCA4531 based) on OpenWrt 19.07 we could force a silent restart of a device with no serial output when we were sending a high amount of UDP traffic (iperf3 at 80 MBit/s in both directions from external hosts, saturating the wifi and causing a load of about 4.5 to 6) and were then triggering an ath9k_queue_reset().
Further debugging showed that the restart was caused by the ath79 watchdog. With disabled watchdog we could observe that the device was constantly going into ath_isr() interrupt handler and was returning early after the ATH_OP_HW_RESET flag test, without clearing any interrupts. Even though ath9k_queue_reset() calls ath9k_hw_kill_interrupts().
With JTAG we could observe the following race condition:
1) ath9k_queue_reset() ... -> ath9k_hw_kill_interrupts() -> set_bit(ATH_OP_HW_RESET, &common->op_flags); ... <- returns
2) ath9k_tasklet() ... -> ath9k_hw_resume_interrupts() ... <- returns
3) loops around: ... handle_int() -> ath_isr() ... -> if (test_bit(ATH_OP_HW_RESET, &common->op_flags)) return IRQ_HANDLED;
x) ath_reset_internal(): => never reached <=
And in ath_isr() we would typically see the following interrupts / interrupt causes:
* status: 0x00111030 or 0x00110030 * async_cause: 2 (AR_INTR_MAC_IPQ) * sync_cause: 0
So the ath9k_tasklet() reenables the ath9k interrupts through ath9k_hw_resume_interrupts() which ath9k_queue_reset() had just disabled. And ath_isr() then keeps firing because it returns IRQ_HANDLED without actually clearing the interrupt.
To fix this IRQ storm also clear/disable the interrupts again when we are in reset state.
Cc: Sven Eckelmann sven@narfation.org Cc: Simon Wunderlich sw@simonwunderlich.de Cc: Linus Lüssing linus.luessing@c0d3.blue Fixes: 872b5d814f99 ("ath9k: do not access hardware on IRQs during reset") Signed-off-by: Linus Lüssing ll@simonwunderlich.de Signed-off-by: Kalle Valo kvalo@codeaurora.org Link: https://lore.kernel.org/r/20210914192515.9273-3-linus.luessing@c0d3.blue Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/wireless/ath/ath9k/main.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c index 173960682ea06..507d8c5149686 100644 --- a/drivers/net/wireless/ath/ath9k/main.c +++ b/drivers/net/wireless/ath/ath9k/main.c @@ -529,8 +529,10 @@ irqreturn_t ath_isr(int irq, void *dev) ath9k_debug_sync_cause(sc, sync_cause); status &= ah->imask; /* discard unasked-for bits */
- if (test_bit(ATH_OP_HW_RESET, &common->op_flags)) + if (test_bit(ATH_OP_HW_RESET, &common->op_flags)) { + ath9k_hw_kill_interrupts(sc->sc_ah); return IRQ_HANDLED; + }
/* * If there are no status bits set, then this interrupt was not