Re: [PATCH] arm64: iort: take _DMA methods into account for named components

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Mon, Apr 20, 2020 at 10:58:02AM +0200, Ard Biesheuvel wrote:
> On Mon, 20 Apr 2020 at 10:41, Lorenzo Pieralisi
> <lorenzo.pieralisi@arm.com> wrote:
> >
> > On Sat, Apr 04, 2020 at 09:30:47AM +0200, Ard Biesheuvel wrote:
> > > Where IORT nodes for named components can describe simple DMA limits
> > > expressed as the number of address bits a device can driver, _DMA methods
> > > in AML can express more complex topologies, involving DMA translation in
> > > particular.
> > >
> > > Currently, we only take this _DMA method into account if it appears on a
> > > ACPI device node describing a PCIe root complex, but it is perfectly
> > > acceptable to attach them to named components as well, so let's ensure
> > > we take them into account in those cases too.
> > >
> > > Reported-by: Andrei Warkentin <awarkentin@vmware.com>
> > > Fixes: 7ad4263980826e8b ("ACPI: Make acpi_dma_configure() DMA regions aware")
> > > Cc: <stable@vger.kernel.org> # v4.14+
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > >  drivers/acpi/arm64/iort.c | 11 ++++-------
> > >  1 file changed, 4 insertions(+), 7 deletions(-)
> >
> > Only question is whether there is FW in the field with _DMA methods that
> > now we would start parsing (and hopefully everything will still work)
> > but for that the only choice is applying this patch and see, so:
> >
> 
> Perhaps it would be better to call acpi_dma_get_range() on dev->parent then?

I think it is fine as it is -  maybe we can hold off sending it all
the way to stable kernels until we are confident it does not cause
unintended breakage ?

Anyway, thanks for putting it together.

Minor nit: I'd make "arm64: iort:" in the subject "ACPI/IORT:"
just to keep logs uniform.

Thanks,
Lorenzo

> > Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> >
> > > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > > index ed3d2d1a7ae9..07eb78baf198 100644
> > > --- a/drivers/acpi/arm64/iort.c
> > > +++ b/drivers/acpi/arm64/iort.c
> > > @@ -1146,13 +1146,10 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size)
> > >       else
> > >               size = 1ULL << 32;
> > >
> > > -     if (dev_is_pci(dev)) {
> > > -             ret = acpi_dma_get_range(dev, &dmaaddr, &offset, &size);
> > > -             if (ret == -ENODEV)
> > > -                     ret = rc_dma_get_range(dev, &size);
> > > -     } else {
> > > -             ret = nc_dma_get_range(dev, &size);
> > > -     }
> > > +     ret = acpi_dma_get_range(dev, &dmaaddr, &offset, &size);
> > > +     if (ret == -ENODEV)
> > > +             ret = dev_is_pci(dev) ? rc_dma_get_range(dev, &size)
> > > +                                   : nc_dma_get_range(dev, &size);
> > >
> > >       if (!ret) {
> > >               /*
> > > --
> > > 2.17.1
> > >

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