[PATCH v10] PCI: tango: Add MSI controller support

[Bjorn Helgaas]

On Tue, Aug 22, 2017 at 09:03:41PM +0100, Marc Zyngier wrote:
> On Tue, Aug 22 2017 at  8:02:18 pm BST, Marc Gonzalez <marc_gonzalez at sigmadesigns.com> wrote:
> > On 22/08/2017 18:29, Marc Zyngier wrote:
> >
> >> On 22/08/17 15:56, Marc Gonzalez wrote:
> >>
> >>>  #define SMP8759_MUX		0x48
> >>>  #define SMP8759_TEST_OUT	0x74
> >>> +#define SMP8759_STATUS		0x80
> >>> +#define SMP8759_ENABLE		0xa0
> >>> +#define SMP8759_DOORBELL	0xa002e07c
> >> 
> >> Why is this hardcoded and not coming from the device-tree, just like any
> >> other address property?
> >
> > Since this bus address is software-configurable, I didn't think
> > it belonged in the DT. Also, I didn't see anything similar in
> > other binding docs, especially
> >
> > Documentation/devicetree/bindings/interrupt-controller/msi.txt
> 
> If that's software configurable, how on Earth did you pick the address?
> How do you ensure that it doesn't conflict with DMA? How is it
> configured into the RC?

But we *do* need to resolve this.  This does seem like an address that
shouldn't be hard-coded into the driver.  Since this driver is
programming the address into an MSI message, but not into the receiver
of that message, there's a coordination issue between this driver and
whatever other software does that receiver configuration.

Bjorn