On 6/7/2021 4:58 PM, Punit Agrawal wrote:
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Commit fede8526cc48 ("PCI: of: Warn if non-prefetchable memory
aperture size is > 32-bit") introduced a warning for non-prefetchable
resources that need more than 32bits to resolve. It turns out that the
check is too restrictive and should be applicable to only resources
that are limited to host bridge windows that don't have the ability to
map 64-bit address space.
I think the host bridge windows having the ability to map 64-bit address
space is different from restricting the non-prefetchable memory aperture
size to 32-bit.
Whether the host bridge uses internal translations or not to map the
non-prefetchable resources to 64-bit space, the size needs to be
programmed in the host bridge's 'Memory Limit Register (Offset 22h)'
which can represent sizes only fit into 32-bits.
Host bridges having the ability to map 64-bit address spaces gives
flexibility to utilize the vast 64-bit space for the (restrictive)
non-prefetchable memory (i.e. mapping non-prefetchable BARs of endpoints
to the 64-bit space in CPU's view) and get it translated internally and
put a 32-bit address on the PCIe bus finally.
- Vidya Sagar
Relax the condition to only warn when the resource size requires >
32-bits and doesn't allow mapping to 64-bit addresses.
Link: https://lore.kernel.org/r/7a1e2ebc-f7d8-8431-d844-41a9c36a8911@xxxxxxx
Signed-off-by: Punit Agrawal <punitagrawal@xxxxxxxxx>
Tested-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Cc: Vidya Sagar <vidyas@xxxxxxxxxx>
---
drivers/pci/of.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 1e45186a5715..38fe2589beb0 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -581,7 +581,8 @@ static int pci_parse_request_of_pci_ranges(struct device *dev,
res_valid |= !(res->flags & IORESOURCE_PREFETCH);
if (!(res->flags & IORESOURCE_PREFETCH))
- if (upper_32_bits(resource_size(res)))
+ if (!(res->flags & IORESOURCE_MEM_64) &&
+ upper_32_bits(resource_size(res)))
dev_warn(dev, "Memory resource size exceeds max for 32 bits\n");
break;
--
2.30.2
