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iommu/of: Prepare for deferred IOMMU configuration 

IOMMU configuration represents unchanging properties of the hardware,
and as such should only need happen once in a device's lifetime, but
the necessary interaction with the IOMMU device and driver complicates
exactly when that point should be.

Since the only reasonable tool available for handling the inter-device
dependency is probe deferral, we need to prepare of_iommu_configure()
to run later than it is currently called (i.e. at driver probe rather
than device creation), to handle being retried, and to tell whether a
not-yet present IOMMU should be waited for or skipped (by virtue of
having declared a built-in driver or not).

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Robin Murphy 2017-04-10 16:50:57 +05:30 committed by Joerg Roedel
parent 2a0c57545a
commit d7b0558230
1 changed files with 42 additions and 1 deletions
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43
drivers/iommu/of_iommu.c
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@ -96,6 +96,19 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
}
EXPORT_SYMBOL_GPL(of_get_dma_window);
static bool of_iommu_driver_present(struct device_node *np)
{
/*
* If the IOMMU still isn't ready by the time we reach init, assume
* it never will be. We don't want to defer indefinitely, nor attempt
* to dereference __iommu_of_table after it's been freed.
*/
if (system_state > SYSTEM_BOOTING)
return false;
return of_match_node(&__iommu_of_table, np);
}
static const struct iommu_ops
*of_iommu_xlate(struct device *dev, struct of_phandle_args *iommu_spec)
{
@ -104,12 +117,20 @@ static const struct iommu_ops
int err;
ops = iommu_ops_from_fwnode(fwnode);
if (!ops || !ops->of_xlate)
if ((ops && !ops->of_xlate) ||
(!ops && !of_iommu_driver_present(iommu_spec->np)))
return NULL;
err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
if (err)
return ERR_PTR(err);
/*
* The otherwise-empty fwspec handily serves to indicate the specific
* IOMMU device we're waiting for, which will be useful if we ever get
* a proper probe-ordering dependency mechanism in future.
*/
if (!ops)
return ERR_PTR(-EPROBE_DEFER);
err = ops->of_xlate(dev, iommu_spec);
if (err)
@ -186,14 +207,34 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
struct device_node *master_np)
{
const struct iommu_ops *ops;
struct iommu_fwspec *fwspec = dev->iommu_fwspec;
if (!master_np)
return NULL;
if (fwspec) {
if (fwspec->ops)
return fwspec->ops;
/* In the deferred case, start again from scratch */
iommu_fwspec_free(dev);
}
if (dev_is_pci(dev))
ops = of_pci_iommu_init(to_pci_dev(dev), master_np);
else
ops = of_platform_iommu_init(dev, master_np);
/*
* If we have reason to believe the IOMMU driver missed the initial
* add_device callback for dev, replay it to get things in order.
*/
if (!IS_ERR_OR_NULL(ops) && ops->add_device &&
dev->bus && !dev->iommu_group) {
int err = ops->add_device(dev);
if (err)
ops = ERR_PTR(err);
}
return IS_ERR(ops) ? NULL : ops;
}