linux-kernel - Re: [PATCH 1/2] of_pci_irq: add a check to fallback to standard device tree parsing

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Date:   Tue, 06 Feb 2018 08:36:24 +1100
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Ryder Lee <ryder.lee@...iatek.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Arnd Bergmann <arnd@...db.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-mediatek@...ts.infradead.org, linux-pci@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Frank Rowand <frowand.list@...il.com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] of_pci_irq: add a check to fallback to standard
 device tree parsing

On Fri, 2018-02-02 at 17:32 +0800, Ryder Lee wrote:
> On Wed, 2018-01-31 at 10:02 -0600, Rob Herring wrote:
> > On Wed, Jan 31, 2018 at 1:41 AM, Ryder Lee <ryder.lee@...iatek.com> wrote:
> > > A root complex usually consist of a host bridge and multiple P2P bridges,
> > > and someone may express that in the form of a root node with many subnodes
> > > and list all four interrupts for each slot (child node) in the root node
> > > like this:
> > > 
> > >          pcie-controller {
> > >                  ...
> > >                  interrupt-map-mask = <0xf800 0 0 7>;
> > >                  interrupt-map = <0x0000 0 0 {INTx} &{interrupt parent} ...>
> > >                                   0x0800 0 0 {INTx} &{interrupt parent} ...>;
> > > 
> > >                  pcie@0,0 {
> > >                          reg = <0x0000 0 0 0 0>;
> > >                          ...
> > >                  };
> > > 
> > >                  pcie@1,0 {
> > >                          reg = <0x0800 0 0 0 0>;
> > >                          ...
> > >                  };
> > >          };
> > > 
> > > As shown above, we'd like to propagate IRQs from a root port to the devices
> > > in the hierarchy below it in this way.  However, it seems that the current
> > > parser couldn't handle such cases and will get something unexpected below:
> > > 
> > >          pcieport 0000:00:01.0: assign IRQ: got 213
> > >          igb 0000:01:00.0: assign IRQ: got 212
> > > 
> > > There is a device which is connected to 2nd slot, but the port doesn't share
> > > the same IRQ with its downstream devices.  The problem here is that, if the
> > > loop found a P2P bridge, it wouldn't check whether the reg property exists
> > > in ppnode or not but just pass the subordinate devfn to of_irq_parse_raw(),
> > > thus the subsequent flow couldn't correctly resolve them.

I don't really understand the problem explanation here. Something
doesn't look right as you shouldn't have to change that function, but I
just don't get what you a

Cheers,
Ben.