On 2018-07-16 4:10 PM, Lorenzo Pieralisi wrote:
On Tue, Jul 10, 2018 at 05:13:45PM +0100, Robin Murphy wrote:
IORT revision D allows PCI root complex nodes to specify a memory
address size limit equivalently to named components, to help describe
straightforward integrations which don't really warrant a full-blown
_DMA method. Now that our headers are up-to-date, plumb it in.
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
---
drivers/acpi/arm64/iort.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 7a3a541046ed..4a66896e2aa3 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -947,6 +947,24 @@ static int nc_dma_get_range(struct device *dev, u64 *size)
return 0;
}
+static int rc_dma_get_range(struct device *dev, u64 *size)
+{
+ struct acpi_iort_node *node;
+ struct acpi_iort_root_complex *rc;
+
+ node = iort_scan_node(ACPI_IORT_NODE_PCI_ROOT_COMPLEX,
+ iort_match_node_callback, dev);
+ if (!node || node->revision < 1)
+ return -ENODEV;
+
+ rc = (struct acpi_iort_root_complex *)node->node_data;
+
+ *size = rc->memory_address_limit >= 64 ? U64_MAX :
+ 1ULL<<rc->memory_address_limit;
+
+ return 0;
+}
+
/**
* iort_dma_setup() - Set-up device DMA parameters.
*
@@ -975,10 +993,13 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size)
size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
- if (dev_is_pci(dev))
+ if (dev_is_pci(dev)) {
ret = acpi_dma_get_range(dev, &dmaaddr, &offset, &size);
- else
+ if (ret == -ENODEV)
+ ret = rc_dma_get_range(dev, &size);
Thank you for putting together the patch.
The question is whether it is OK to ignore the IORT address limits
when _DMA is actually specified. It is a sort of grey area that
has to be clarified, maybe we can add a check to detect a size
mismatch, I do not know if something should be added at IORT spec
level to clarify its relation to the _DMA object, if present.
Yeah, I'm assuming that _DMA would be used to describe conditions more
specific than the simple address size limit (i.e. bridge windows), so
even if both are present, the range inferred from _DMA will always be
less than or equal to that inferred from IORT, and thus rather than
explicitly calculating the intersection of the two we can simply do this
short-circuit.
If IORT accurately reflects the total number of usable address bits,
then I can't see that it would ever make sense for _DMA to specify an
address range which exceeds that; I guess it comes down to how much
effort we want to spend verifying firmware instead of trusting it.
Robin.
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