Thierry Reding <thierry.reding@xxxxxxxxx> wrote @ Fri, 1 Nov 2013 10:52:24 +0100:
> * PGP Signed by an unknown key
>
> On Fri, Nov 01, 2013 at 08:49:09AM +0200, Hiroshi Doyu wrote:
> > On Thu, 31 Oct 2013 18:53:22 +0100
> > Stephen Warren <swarren@xxxxxxxxxxxxx> wrote:
> > ...
> > > We're talking about memory-mapped on-SoC devices here, that generally
> > > only exist inside Tegra SoCs.
> > >
> > > Even ignoring that (i.e. expanding the argument to arbitrary modules),
> > > having drivers that perform bus-master transactions call a function
> > > of_iommu_attach() or similar, which does nothing if the device isn't
> > > behind an IOMMU but otherwise does whatever is required, seems like it
> > > isn't much of an imposition.
> >
> > Where do you expect of_iommu_attach() to be called?
> > I thought something below:
> >
> > Modified drivers/base/dd.c
> > diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> > index 35fa368..92ec2e9 100644
> > --- a/drivers/base/dd.c
> > +++ b/drivers/base/dd.c
> > @@ -278,6 +278,10 @@ static int really_probe(struct device *dev, struct device_driver *drv)
> > if (ret)
> > goto probe_failed;
> >
> > + ret = of_iommu_attach(dev);
> > + if (ret)
> > + goto probe_failed;
> > +
> > if (driver_sysfs_add(dev)) {
> > printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
> > __func__, dev_name(dev));
> >
>
> The patches for late interrupt reference resolution introduced a
> separate function, of_platform_probe(), with the intent of having it
> call potentially many resource allocation hooks. The function needs to
> be platform_device specific, and therefore is called from within the
> platform_drv_probe() function. The reason is that interrupts are stored
> as resources within struct platform_device, so you need to have access
> to a platform device.
Ok.
Also I think that a special new /section/ with hooks[1] would fit with
this as well.
> I think that devices that require attachment to an IOMMU will always end
> up being platform devices too, so even if it isn't a strict requirement
> here it would still make sense to use a similar infrastructure to avoid
> cluttering the core code with too many loose function calls.
FYI: PCIe devices can also be IOMMU'able although not yet enabled yet.
[1] http://lists.linuxfoundation.org/pipermail/iommu/2013-November/006874.html
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