On Sun, May 15, 2022 at 01:10:38PM +0200, Janne Grunau wrote: > On 2022-05-12 21:00:49 +0200, Thierry Reding wrote: > > From: Thierry Reding <[email protected]> > > > > This is an implementation that IOMMU drivers can use to obtain reserved > > memory regions from a device tree node. It uses the reserved-memory DT > > bindings to find the regions associated with a given device. If these > > regions are marked accordingly, identity mappings will be created for > > them in the IOMMU domain that the devices will be attached to. > > > > Signed-off-by: Thierry Reding <[email protected]> > > --- > > Changes in v5: > > - update for new "iommu-addresses" device tree bindings > > > > Changes in v4: > > - fix build failure on !CONFIG_OF_ADDRESS > > > > Changes in v3: > > - change "active" property to identity mapping flag that is part of the > > memory region specifier (as defined by #memory-region-cells) to allow > > per-reference flags to be used > > > > Changes in v2: > > - use "active" property to determine whether direct mappings are needed > > > > drivers/iommu/of_iommu.c | 90 ++++++++++++++++++++++++++++++++++++++++ > > include/linux/of_iommu.h | 8 ++++ > > 2 files changed, 98 insertions(+) > > > > diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c > > index 5696314ae69e..9e341b5e307f 100644 > > --- a/drivers/iommu/of_iommu.c > > +++ b/drivers/iommu/of_iommu.c > > @@ -11,12 +11,15 @@ > > #include <linux/module.h> > > #include <linux/msi.h> > > #include <linux/of.h> > > +#include <linux/of_address.h> > > #include <linux/of_iommu.h> > > #include <linux/of_pci.h> > > #include <linux/pci.h> > > #include <linux/slab.h> > > #include <linux/fsl/mc.h> > > > > +#include <dt-bindings/reserved-memory.h> > > + > > #define NO_IOMMU 1 > > > > static int of_iommu_xlate(struct device *dev, > > @@ -172,3 +175,90 @@ const struct iommu_ops *of_iommu_configure(struct > > device *dev, > > > > return ops; > > } > > + > > +/** > > + * of_iommu_get_resv_regions - reserved region driver helper for device > > tree > > + * @dev: device for which to get reserved regions > > + * @list: reserved region list > > + * > > + * IOMMU drivers can use this to implement their .get_resv_regions() > > callback > > + * for memory regions attached to a device tree node. See the > > reserved-memory > > + * device tree bindings on how to use these: > > + * > > + * Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt > > + */ > > +void of_iommu_get_resv_regions(struct device *dev, struct list_head *list) > > +{ > > +#if IS_ENABLED(CONFIG_OF_ADDRESS) > > + struct of_phandle_iterator it; > > + int err; > > + > > + of_for_each_phandle(&it, err, dev->of_node, "memory-region", NULL, 0) { > > + struct iommu_resv_region *region; > > + struct resource res; > > + const __be32 *maps; > > + int size; > > Adding 'if (!of_device_is_available(it.node)) continue;' here would help > backwards compatibility. My plan was to add the reserved regions with > "iommu-addresses" with all zero adresses and sizes with status = > "disabled" to the devicetree. A bootloader update is required to fill > those.
Yes, good point. My plan was originally to have the bootloader/firmware
generate these nodes in their entirety, but yeah, prepopulating them and
having firmware just fill in updated values and setting status = "okay"
seems reasonable to me.
> > +
> > + memset(&res, 0, sizeof(res));
> > +
> > + /*
> > + * The "reg" property is optional and can be omitted by
> > reserved-memory regions
> > + * that represent reservations in the IOVA space, which are
> > regions that should
> > + * not be mapped.
> > + */
> > + if (of_find_property(it.node, "reg", NULL)) {
> > + err = of_address_to_resource(it.node, 0, &res);
> > + if (err < 0) {
> > + dev_err(dev, "failed to parse memory region
> > %pOF: %d\n",
> > + it.node, err);
> > + continue;
> > + }
> > + }
> > +
> > + maps = of_get_property(it.node, "iommu-addresses", &size);
> > + if (maps) {
> > + const __be32 *end = maps + size / sizeof(__be32);
> > + struct device_node *np;
> > + unsigned int index = 0;
> > + u32 phandle;
> > + int na, ns;
> > +
> > + while (maps < end) {
> > + phys_addr_t start, end;
> > + size_t length;
> > +
> > + phandle = be32_to_cpup(maps++);
> > + np = of_find_node_by_phandle(phandle);
> > + na = of_n_addr_cells(np);
> > + ns = of_n_size_cells(np);
> > +
> > + start = of_translate_dma_address(np, maps);
> > + length = of_read_number(maps + na, ns);
>
> alternatively we could handle mappings/reservations with length 0 as
> error and skip them.
I think we could do both.
Thanks for the feedback,
Thierry
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