wifi: ath11k: fix race due to setting ATH11K_FLAG_EXT_IRQ_ENABLED too early

We are seeing below error randomly in the case where only
one MSI vector is configured:

kernel: ath11k_pci 0000:03:00.0: wmi command 16387 timeout

The reason is, currently, in ath11k_pcic_ext_irq_enable(),
ATH11K_FLAG_EXT_IRQ_ENABLED is set before NAPI is enabled.
This results in a race condition: after
ATH11K_FLAG_EXT_IRQ_ENABLED is set but before NAPI enabled,
CE interrupt breaks in. Since IRQ is shared by CE and data
path, ath11k_pcic_ext_interrupt_handler() is also called
where we call disable_irq_nosync() to disable IRQ. Then
napi_schedule() is called but it does nothing because NAPI
is not enabled at that time, meaning
ath11k_pcic_ext_grp_napi_poll() will never run, so we have
no chance to call enable_irq() to enable IRQ back. Finally
we get above error.

Fix it by setting ATH11K_FLAG_EXT_IRQ_ENABLED after all
NAPI and IRQ work are done. With the fix, we are sure that
by the time ATH11K_FLAG_EXT_IRQ_ENABLED is set, NAPI is
enabled.

Note that the fix above also introduce some side effects:
if ath11k_pcic_ext_interrupt_handler() breaks in after NAPI
enabled but before ATH11K_FLAG_EXT_IRQ_ENABLED set, nothing
will be done by the handler this time, the work will be
postponed till the next time the IRQ fires.

Tested-on: WCN6855 hw2.1 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.23

Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20231117003919.26218-1-quic_bqiang@quicinc.com

diff --git a/drivers/net/wireless/ath/ath11k/pcic.c b/drivers/net/wireless/ath/ath11k/pcic.c
index 90d8936a3e2eb285d9e4a32deea5597caab81911..15e2ceb22a44d752145f824952b8855d293caa21 100644 (file)
--- a/drivers/net/wireless/ath/ath11k/pcic.c
+++ b/drivers/net/wireless/ath/ath11k/pcic.c
@@ -460,8 +460,6 @@ void ath11k_pcic_ext_irq_enable(struct ath11k_base *ab)
 {
        int i;
 
-       set_bit(ATH11K_FLAG_EXT_IRQ_ENABLED, &ab->dev_flags);
-
        for (i = 0; i < ATH11K_EXT_IRQ_GRP_NUM_MAX; i++) {
                struct ath11k_ext_irq_grp *irq_grp = &ab->ext_irq_grp[i];
 
@@ -471,6 +469,8 @@ void ath11k_pcic_ext_irq_enable(struct ath11k_base *ab)
                }
                ath11k_pcic_ext_grp_enable(irq_grp);
        }
+
+       set_bit(ATH11K_FLAG_EXT_IRQ_ENABLED, &ab->dev_flags);
 }
 EXPORT_SYMBOL(ath11k_pcic_ext_irq_enable);