Re: [PATCH V2 1/2] ACPI / scan: Support multiple dma windows with different offsets

From: Jianmin Lv
Date: Mon Aug 29 2022 - 09:07:07 EST



On 2022/8/12 下午3:52, Lorenzo Pieralisi wrote:
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

Hi, Robin and Lorenzo

For the issue of empty _DMA, I consulted ASWG(ACPI Spec Work Group), and received an reply from some people that an _DMA object is allowed to contain *no* resources, and indicates disabled DMA(some arm systems are being used empty _DMA as an indicator to the OS that DMA is disabled for specified device). ASWG has isssued an request to clarify it in spec after approved.


I think we can submit a seperate patch for that after it is confirmed.

Thanks.

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;
}