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 <[email protected]>
Acked-by: Jeff Johnson <[email protected]>
Signed-off-by: Kalle Valo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Baochen Qiang

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);