Re: [PATCH v5 1/4] PCI: xilinx: Create legacy IRQ domain with size 5

[Ley Foon Tan <ley.foon.tan@intel.com>]

On Mon, 2017-06-19 at 18:47 -0500, Bjorn Helgaas wrote:
> [+cc Thomas, Ley Foon]
> 
> On Sat, Jun 17, 2017 at 12:57:38PM -0700, Paul Burton wrote:
> > 
> > The driver expects to use hardware IRQ numbers 1 through 4 for INTX
> > interrupts, but only creates an IRQ domain of size 4 (ie. IRQ
> > numbers 0
> > through 3). This results in a warning from irq_domain_associate
> > when it
> > is called with hwirq=4:
> > 
> >      WARNING: CPU: 0 PID: 1 at kernel/irq/irqdomain.c:365
> >          irq_domain_associate+0x170/0x220
> >      error: hwirq 0x4 is too large for dummy
> >      Modules linked in:
> >      CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W
> >          4.12.0-rc5-00126-g19e1b3a10aad-dirty #427
> >      Stack : 0000000000000000 0000000000000004 0000000000000006
> > ffffffff8092c78a
> >              0000000000000061 ffffffff8018bf60 0000000000000000
> > 0000000000000000
> >              ffffffff8088c287 ffffffff80811d18 a8000000ffc60000
> > ffffffff80926678
> >              0000000000000001 0000000000000000 ffffffff80887880
> > ffffffff80960000
> >              ffffffff80920000 ffffffff801e6744 ffffffff80887880
> > a8000000ffc4f8f8
> >              000000000000089c ffffffff8018d260 0000000000010000
> > ffffffff80811d18
> >              0000000000000000 0000000000000001 0000000000000000
> > 0000000000000000
> >              0000000000000000 a8000000ffc4f840 0000000000000000
> > ffffffff8042cf34
> >              0000000000000000 0000000000000000 0000000000000000
> > 0000000000040c00
> >              0000000000000000 ffffffff8010d1c8 0000000000000000
> > ffffffff8042cf34
> >              ...
> >      Call Trace:
> >      [<ffffffff8010d1c8>] show_stack+0x80/0xa0
> >      [<ffffffff8042cf34>] dump_stack+0xd4/0x110
> >      [<ffffffff8013ea98>] __warn+0xf0/0x108
> >      [<ffffffff8013eb14>] warn_slowpath_fmt+0x3c/0x48
> >      [<ffffffff80196528>] irq_domain_associate+0x170/0x220
> >      [<ffffffff80196bf0>] irq_create_mapping+0x88/0x118
> >      [<ffffffff801976a8>] irq_create_fwspec_mapping+0xb8/0x320
> >      [<ffffffff80197970>] irq_create_of_mapping+0x60/0x70
> >      [<ffffffff805d1318>] of_irq_parse_and_map_pci+0x20/0x38
> >      [<ffffffff8049c210>] pci_fixup_irqs+0x60/0xe0
> >      [<ffffffff8049cd64>] xilinx_pcie_probe+0x28c/0x478
> >      [<ffffffff804e8ca8>] platform_drv_probe+0x50/0xd0
> >      [<ffffffff804e73a4>] driver_probe_device+0x2c4/0x3a0
> >      [<ffffffff804e7544>] __driver_attach+0xc4/0xd0
> >      [<ffffffff804e5254>] bus_for_each_dev+0x64/0xa8
> >      [<ffffffff804e5e40>] bus_add_driver+0x1f0/0x268
> >      [<ffffffff804e8000>] driver_register+0x68/0x118
> >      [<ffffffff801001a4>] do_one_initcall+0x4c/0x178
> >      [<ffffffff808d3ca8>] kernel_init_freeable+0x204/0x2b0
> >      [<ffffffff80730b68>] kernel_init+0x10/0xf8
> >      [<ffffffff80106218>] ret_from_kernel_thread+0x14/0x1c
> > 
> > This patch avoids that warning by creating the legacy IRQ domain
> > with
> > size 5 rather than 4, allowing it to cover the hwirq=4/INTD case.
> > 
> > Signed-off-by: Paul Burton <paul.burton@imgtec.com>
> > Cc: Bharat Kumar Gogada <bharatku@xilinx.com>
> > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > Cc: Michal Simek <michal.simek@xilinx.com>
> > Cc: Ravikiran Gummaluri <rgummal@xilinx.com>
> > Cc: linux-pci@vger.kernel.org
> > 
> > ---
> > 
> > Changes in v5:
> > - New patch; replacing "PCI: xilinx: Fix INTX irq dispatch".
> > 
> > Changes in v4: None
> > Changes in v3: None
> > Changes in v2: None
> > 
> >  drivers/pci/host/pcie-xilinx.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/host/pcie-xilinx.c
> > b/drivers/pci/host/pcie-xilinx.c
> > index 2fe2df51f9f8..94c71fb91648 100644
> > --- a/drivers/pci/host/pcie-xilinx.c
> > +++ b/drivers/pci/host/pcie-xilinx.c
> > @@ -524,7 +524,7 @@ static int xilinx_pcie_init_irq_domain(struct
> > xilinx_pcie_port *port)
> >               return -ENODEV;
> >       }
> > 
> > -     port->leg_domain = irq_domain_add_linear(pcie_intc_node, 4,
> > +     port->leg_domain = irq_domain_add_linear(pcie_intc_node, 1 +
> > 4,
> I don't understand this.  Several drivers call
> irq_domain_add_linear() with
> a size of 4:
> 
>   dra7xx_pcie_init_irq_domain
>   ks_dw_pcie_host_init
>   advk_pcie_init_irq_domain
>   faraday_pci_setup_cascaded_irq
>   rockchip_pcie_init_irq_domain
>   nwl_pcie_init_irq_domain
> 
> Only one other in drivers/pci uses a size of 5:
> 
>   altera_pcie_init_irq_domain
> 
> Why can't we use a size of 4 for all of them?  We only have INTA-
> INTD.  Are
> altera and xilinx missing something to apply an offset from the 0-3
> space
> to the 1-4 space?
We have the same discussion before in 2016: https://lkml.org/lkml/2016/
8/30/198

This is because legacy interrupt is start with index 1 instead of 0.

> 
> > 
> >                                                &intx_domain_ops,
> >                                                port);
> >       if (!port->leg_domain) {
> > --
> > 2.13.1
> > 
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