ACPI: Introduce DMA ranges parsing

Some devices have limited addressing capabilities and cannot
reference the whole memory address space while carrying out DMA
operations (eg some devices with bus address bits range smaller than
system bus - which prevents them from using bus addresses that are
otherwise valid for the system).

The ACPI _DMA object allows bus devices to define the DMA window that is
actually addressable by devices that sit upstream the bus, therefore
providing a means to parse and initialize the devices DMA masks and
addressable DMA range size.

By relying on the generic ACPI kernel layer to retrieve and parse
resources, introduce ACPI core code to parse the _DMA object.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 79 insertions, 0 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 33897298f03e..94500d99f2d6 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1360,6 +1360,85 @@ enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
 }
 
 /**
+ * acpi_dma_get_range() - Get device DMA parameters.
+ *
+ * @dev: device to configure
+ * @dma_addr: pointer device DMA address result
+ * @offset: pointer to the DMA offset result
+ * @size: pointer to DMA range size result
+ *
+ * Evaluate DMA regions and return respectively DMA region start, offset
+ * and size in dma_addr, offset and size on parsing success; it does not
+ * update the passed in values on failure.
+ *
+ * Return 0 on success, < 0 on failure.
+ */
+int acpi_dma_get_range(struct device *dev, u64 *dma_addr, u64 *offset,
+		       u64 *size)
+{
+	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;
+
+	/*
+	 * Walk the device tree chasing an ACPI companion with a _DMA
+	 * object while we go. Stop if we find a device with an ACPI
+	 * companion containing a _DMA method.
+	 */
+	do {
+		adev = ACPI_COMPANION(dma_dev);
+		if (adev && acpi_has_method(adev->handle, METHOD_NAME__DMA))
+			break;
+
+		dma_dev = dma_dev->parent;
+	} while (dma_dev);
+
+	if (!dma_dev)
+		return -ENODEV;
+
+	if (!acpi_has_method(adev->handle, METHOD_NAME__CRS)) {
+		acpi_handle_warn(adev->handle, "_DMA is valid only if _CRS is present\n");
+		return -EINVAL;
+	}
+
+	ret = acpi_dev_get_dma_resources(adev, &list);
+	if (ret > 0) {
+		list_for_each_entry(rentry, &list, node) {
+			if (dma_offset && rentry->offset != dma_offset) {
+				ret = -EINVAL;
+				dev_warn(dma_dev, "Can't handle multiple windows with different offsets\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;
+		}
+
+		*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);
+
+	return ret >= 0 ? 0 : ret;
+}
+
+/**
  * acpi_dma_configure - Set-up DMA configuration for the device.
  * @dev: The pointer to the device
  * @attr: device dma attributes