On Fri, Aug 05, 2022 at 01:46:07PM +0100, Robin Murphy wrote:
[...]
> > -int acpi_dma_get_range(struct device *dev, u64 *dma_addr, u64 *offset,
> > - u64 *size)
> > +int acpi_dma_get_range(struct device *dev, const struct bus_dma_region **map)
> > {
> > struct acpi_device *adev;
> > LIST_HEAD(list);
> > struct resource_entry *rentry;
> > int ret;
> > struct device *dma_dev = dev;
> > - u64 len, dma_start = U64_MAX, dma_end = 0, dma_offset = 0;
> > + int num_ranges = 0;
> > + struct bus_dma_region *r;
> > /*
> > * Walk the device tree chasing an ACPI companion with a _DMA
> > @@ -1525,31 +1526,31 @@ int acpi_dma_get_range(struct device *dev, u64 *dma_addr, u64 *offset,
> > ret = acpi_dev_get_dma_resources(adev, &list);
> > if (ret > 0) {
> > + list_for_each_entry(rentry, &list, node)
> > + num_ranges++;
>
> We already have the number of resources in ret.
>
> Looking at this, I also now wonder if we're doing the right thing if the
> object is present but contains no resources. The spec isn't clear whether
> that's even really valid, but if it is, is it meaningful? It seems we'd
> currently consider an empty object equivalent to no object, but if anything
> it should perhaps be interpreted as the opposite, i.e. that no DMA is
> possible because the bus does not decode any ranges. Is anyone more familiar
> with the intent of the spec here?
I think we are currently considering no object differently from an
empty object, since for no object we would return -ENODEV in
acpi_dma_get_range(), we would not even get to parsing the resources
(and return 0) and we would fall back to checking IORT to gather the
DMA address space size.
I think you are right, we should change the behaviour if an object
is present but it has no resources though, by reading the specs an
empty _DMA object implies no DMA is possible and that's not what
we are doing at the moment (hopefully there is no firmware out
there with such a set-up but there is only one way to discover it).
This behavioural change should be a separate patch obviously for
bisectability (and a possible revert).
Lorenzo
> Thanks,
> Robin.
>
> > +
> > + r = kcalloc(num_ranges + 1, sizeof(*r), GFP_KERNEL);
> > + if (!r) {
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + *map = r;
> > +
> > list_for_each_entry(rentry, &list, node) {
> > - if (dma_offset && rentry->offset != dma_offset) {
> > + if (rentry->res->start >= rentry->res->end) {
> > ret = -EINVAL;
> > - dev_warn(dma_dev, "Can't handle multiple windows with different offsets\n");
> > + dev_dbg(dma_dev, "Invalid DMA regions configuration\n");
> > goto out;
> > }
> > - dma_offset = rentry->offset;
> > -
> > - /* Take lower and upper limits */
> > - if (rentry->res->start < dma_start)
> > - dma_start = rentry->res->start;
> > - if (rentry->res->end > dma_end)
> > - dma_end = rentry->res->end;
> > - }
> > - if (dma_start >= dma_end) {
> > - ret = -EINVAL;
> > - dev_dbg(dma_dev, "Invalid DMA regions configuration\n");
> > - goto out;
> > + r->cpu_start = rentry->res->start;
> > + r->dma_start = rentry->res->start - rentry->offset;
> > + r->size = rentry->res->end - rentry->res->start + 1;
> > + r->offset = rentry->offset;
> > + r++;
> > }
> > - *dma_addr = dma_start - dma_offset;
> > - len = dma_end - dma_start;
> > - *size = max(len, len + 1);
> > - *offset = dma_offset;
> > }
> > out:
> > acpi_dev_free_resource_list(&list);
> > @@ -1639,20 +1640,19 @@ int acpi_dma_configure_id(struct device *dev, enum dev_dma_attr attr,
> > const u32 *input_id)
> > {
> > const struct iommu_ops *iommu;
> > - u64 dma_addr = 0, size = 0;
> > if (attr == DEV_DMA_NOT_SUPPORTED) {
> > set_dma_ops(dev, &dma_dummy_ops);
> > return 0;
> > }
> > - acpi_arch_dma_setup(dev, &dma_addr, &size);
> > + acpi_arch_dma_setup(dev);
> > iommu = acpi_iommu_configure_id(dev, input_id);
> > if (PTR_ERR(iommu) == -EPROBE_DEFER)
> > return -EPROBE_DEFER;
> > - arch_setup_dma_ops(dev, dma_addr, size,
> > + arch_setup_dma_ops(dev, 0, U64_MAX,
> > iommu, attr == DEV_DMA_COHERENT);
> > return 0;
> > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> > index 0dc1ea0b..e106073 100644
> > --- a/include/acpi/acpi_bus.h
> > +++ b/include/acpi/acpi_bus.h
> > @@ -611,8 +611,7 @@ struct acpi_pci_root {
> > int acpi_iommu_fwspec_init(struct device *dev, u32 id,
> > struct fwnode_handle *fwnode,
> > const struct iommu_ops *ops);
> > -int acpi_dma_get_range(struct device *dev, u64 *dma_addr, u64 *offset,
> > - u64 *size);
> > +int acpi_dma_get_range(struct device *dev, const struct bus_dma_region **map);
> > int acpi_dma_configure_id(struct device *dev, enum dev_dma_attr attr,
> > const u32 *input_id);
> > static inline int acpi_dma_configure(struct device *dev,
> > diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> > index 44975c1..34e0545 100644
> > --- a/include/linux/acpi.h
> > +++ b/include/linux/acpi.h
> > @@ -280,12 +280,12 @@ int acpi_table_parse_madt(enum acpi_madt_type id,
> > #ifdef CONFIG_ARM64
> > void acpi_numa_gicc_affinity_init(struct acpi_srat_gicc_affinity *pa);
> > -void acpi_arch_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size);
> > +void acpi_arch_dma_setup(struct device *dev);
> > #else
> > static inline void
> > acpi_numa_gicc_affinity_init(struct acpi_srat_gicc_affinity *pa) { }
> > static inline void
> > -acpi_arch_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size) { }
> > +acpi_arch_dma_setup(struct device *dev) { }
> > #endif
> > int acpi_numa_memory_affinity_init (struct acpi_srat_mem_affinity *ma);
> > @@ -974,8 +974,7 @@ static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
> > return DEV_DMA_NOT_SUPPORTED;
> > }
> > -static inline int acpi_dma_get_range(struct device *dev, u64 *dma_addr,
> > - u64 *offset, u64 *size)
> > +static inline int acpi_dma_get_range(struct device *dev, const struct bus_dma_region **map)
> > {
> > return -ENODEV;
> > }
