Re: [PATCH 7/7] powerpc: Added PCI MSI support using the HSTA module

Benjamin Herrenschmidt
2014-02-21T20:41:26Z

On Fri, 2014-02-21 at 15:33 +0100, Arnd Bergmann wrote:

> > @@ -242,8 +264,10 @@
> > ranges = <0x02000000 0x00000000 0x80000000 0x00000110 0x80000000 0x0 0x80000000
> > 0x01000000 0x0 0x0 0x00000140 0x0 0x0 0x00010000>;
> >
> > - /* Inbound starting at 0 to memsize filled in by zImage */
> > - dma-ranges = <0x42000000 0x0 0x0 0x0 0x0 0x0 0x0>;
> > + /* Inbound starting at 0x0 to 0x40000000000. In order to use MSI
> > + * PCI devices must be able to write to the HSTA module.
> > + */
> > + dma-ranges = <0x42000000 0x0 0x0 0x0 0x0 0x400 0x0>;

Should we (provided it's possible in HW) create two ranges instead ? One
covering RAM and one covering MSIs ? To avoid stray DMAs whacking random
HW registers in the chip ...

> > /* This drives busses 0 to 0xf */
> > bus-range = <0x0 0xf>;
>
> Ah, I first only saw the line you are removing and was about
> to suggest what you do anyway. Great!
>
> > diff --git a/arch/powerpc/sysdev/ppc4xx_pci.c b/arch/powerpc/sysdev/ppc4xx_pci.c
> > index 54ec1d5..7cc3acc 100644
> > --- a/arch/powerpc/sysdev/ppc4xx_pci.c
> > +++ b/arch/powerpc/sysdev/ppc4xx_pci.c
> > @@ -176,8 +176,12 @@ static int __init ppc4xx_parse_dma_ranges(struct pci_controller *hose,
> > return -ENXIO;
> > }
> >
> > - /* Check that we are fully contained within 32 bits space */
> > - if (res->end > 0xffffffff) {
> > + /* Check that we are fully contained within 32 bits space if we are not
> > + * running on a 460sx or 476fpe which have 64 bit bus addresses.
> > + */
> > + if (res->end > 0xffffffff &&
> > + !(of_device_is_compatible(hose->dn, "ibm,plb-pciex-460sx")
> > + || of_device_is_compatible(hose->dn, "ibm,plb-pciex-476fpe"))) {
> > printk(KERN_ERR "%s: dma-ranges outside of 32 bits space\n",
> > hose->dn->full_name);
> > return -ENXIO;
>
> A more general question for BenH: Apparently this PCI implementation is
> getting reused on arm64 for APM X-Gene. Do you see any value in trying to
> share host controller drivers like this one across powerpc and arm64?

I would start duplicating, and see how much common code remains... Then
eventually merge.

> It's possible we are going to see the same situation with fsl_pci in the
> future, if arm and powerpc qoriq chips use the same peripherals. My
> plan for arm64 right now is to make PCI work without any code in arch/,
> just using new helper functions in drivers/pci and sticking the host
> drivers into drivers/pci/host as we started doing for arm32, but it
> can require significant work to make those drivers compatible with
> the powerpc pci-common.c.

powerpc pci-common.c is shrinking :-) At least the address remapping is
all in the core now, we could move more over I suppose...

Cheers,
Ben.

> Arnd
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