linux-kernel - RE: CPU stall with TP-Link wifi PCIe card

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Date:   Wed, 30 Nov 2016 16:50:26 +0000
From:   Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
CC:     Bjorn Helgaas <helgaas@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        "arnd@...db.de" <arnd@...db.de>,
        "manoha@....qualcomm.com" <manoha@....qualcomm.com>
Subject: RE: CPU stall with TP-Link wifi PCIe card

Just to add, im using 4.6 kernel version. And the card is working on ARM, X86 machine.

> Subject: CPU stall with TP-Link wifi PCIe card
> 
> Hi,
> 
> We are testing TP-link wifi PCIe card(TL-WDN4800) on our soc (pcie-xilinx-
> nwl.c). This card is using
> legacy interrupts and it doesn't support MSI.
> 
> When we do scan on wifi interface(using "iw dev wlan0 scan") cpu is getting
> stalled
> making whole system hang.
> 
> After debugging found that IRQ is being disabled after getting 1 or 2 interrupts
> immediately after we run the scan command.
> 
> But interrupts are being received to root port continuously but not being
> serviced by EP due to following
> condition, due to continuous interrupts cpu is getting stalled.
> 
> In handle_simple_irq:
> 
> if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data))) {
>                 desc->istate |= IRQS_PENDING;
>                 goto out_unlock;
>   }
> 
> The irqd_irq_disabled(&desc->irq_data) is returning 1 after 1 or 2 interrupts after
> we scan.
> 
> Can any one tell why irq is going into disabled state ?
> 
> What might be the source that's making it go into disabled state ?
> 
> Thanks & Regards,
> Bharat
>