linux-kernel - RE: [PATCH 3/3] PCI: Xilinx NWL PCIe: Fix Error for multi function device for legacy interrupts.

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Date:   Tue, 30 Aug 2016 14:13:01 +0000
From:   Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
To:     Marc Zyngier <marc.zyngier@....com>,
        "robh@...nel.org" <robh@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "colin.king@...onical.com" <colin.king@...onical.com>,
        Soren Brinkmann <sorenb@...inx.com>,
        Michal Simek <michals@...inx.com>,
        "arnd@...db.de" <arnd@...db.de>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ravikiran Gummaluri <rgummal@...inx.com>
Subject: RE: [PATCH 3/3] PCI: Xilinx NWL PCIe: Fix Error for multi function
 device for legacy interrupts.

> Hi Bharat,
> > @@ -561,7 +561,7 @@ static int nwl_pcie_init_irq_domain(struct nwl_pcie
> *pcie)
> >     }
> >
> >     pcie->legacy_irq_domain = irq_domain_add_linear(legacy_intc_node,
> > -                                                   INTX_NUM,
> > +                                                   INTX_NUM + 1,
> >                                                     &legacy_domain_ops,
> >                                                     pcie);
>
> This feels like the wrong thing to do. You have INTX_NUM irqs, so the domain
> allocation should reflect this. On the other hand, the way the driver currently
> deals with mappings is quite broken (consistently adding 1 to the HW interrupt).
>
Hi Marc,

Without above change I get following crash in kernel while booting.

[    2.441684] error: hwirq 0x4 is too large for dummy

[    2.441694] ------------[ cut here ]------------

[    2.441698] WARNING: at kernel/irq/irqdomain.c:344

[    2.441702] Modules linked in:

[    2.441706]

[    2.441714] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.4.0 #8

[    2.441718] Hardware name: xlnx,zynqmp (DT)

[    2.441723] task: ffffffc071886b80 ti: ffffffc071888000 task.ti: ffffffc071888000

[    2.441732] PC is at irq_domain_associate+0x138/0x1c0

[    2.441738] LR is at irq_domain_associate+0x138/0x1c0

In kernel/irq/irqdomain.c function irq_domain_associate

if (WARN(hwirq >= domain->hwirq_max,
                 "error: hwirq 0x%x is too large for %s\n", (int)hwirq, domain->name))
                return -EINVAL;

Here the hwirq and hwirq_max are equal to 4 without the above condition (INTX_NUM + 1) due to which crash is coming.
This is happening as the legacy interrupts are starting from 1 (INTA).

And I'm  consistently adding 1 to the HW interrupt as in nwl_pcie_leg_handler I get 0th bit set from MSGF_LEG_STATUS
if INTA interrupt is raised but my hwirq number being mapped for INTA is 0x1 so that's I'm adding 1 to obtain correct virtual irq.
Same case in nwl_pcie_free_irq_domain since hwirq starts from one I'm adding 1 to obtain virtual irq and free it.

Thanks & Regards,
Bharat


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