Hi Rob,

Thanks for taking a look.

Rob Herring [off-list ref] writes:

On Wed, May 26, 2021 at 8:35 AM Punit Agrawal [off-list ref] wrote:

quoted

The PCIe host bridge on RK3399 advertises a single address range
marked as 64-bit memory even though it lies entirely below 4GB. While
previously, the OF PCI range parser treated 64-bit ranges more
leniently (i.e., as 32-bit), since commit 9d57e61bf723 ("of/pci: Add
IORESOURCE_MEM_64 to resource flags for 64-bit memory addresses") the
code takes a stricter view and treats the ranges as advertised in the
device tree (i.e, as 64-bit).

The change in behaviour causes failure when allocating bus addresses
to devices connected behind a PCI-to-PCI bridge that require
non-prefetchable memory ranges. The allocation failure was observed
for certain Samsung NVMe drives connected to RockPro64 boards.

Update the host bridge window attributes to treat it as 32-bit address
memory. This fixes the allocation failure observed since commit
9d57e61bf723.

Reported-by: Alexandru Elisei <redacted>
Link: https://lore.kernel.org/r/7a1e2ebc-f7d8-8431-d844-41a9c36a8911@arm.com (local)
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Punit Agrawal <redacted>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Rob Herring <robh+dt@kernel.org>
---
Hi,

The patch fixes the failure observed with detecting certain Samsung
NVMe drives on RK3399 based boards.

Hopefully, the folks on this thread can provide some input on the
reason the host bridge window was originally marked as 64-bit or if
there are any downsides to applying the patch.

We can't require *only* a DT update to fix this. Ideally, the Rockchip
PCI driver should clear the 64-bit flag in the resources though I'm
not sure if the bridge driver would have access early enough.

Following the discussion in the other thread, I tested the following
changes to fixup 64-bit flag for non-prefetchable memory resources that
fit below 4GB.

If the changes look good, I'll send it out as a proper patch later
today.

---->8----

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index da5b414d585a..b9d0bee5a088 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c

@@ -565,10 +565,14 @@ static int pci_parse_request_of_pci_ranges(struct device *dev,
                case IORESOURCE_MEM:
                        res_valid |= !(res->flags & IORESOURCE_PREFETCH);

-                       if (!(res->flags & IORESOURCE_PREFETCH))
+                       if (!(res->flags & IORESOURCE_PREFETCH)) {
                                if (upper_32_bits(resource_size(res)))
                                        dev_warn(dev, "Memory resource size exceeds max for 32 bits\n");
-
+                               if ((res->flags & IORESOURCE_MEM_64) && !upper_32_bits(res->end)) {
+                                       dev_warn(dev, "Overriding 64-bit flag for non-prefetchable memory below 4GB\n");
+                                       res->flags &= ~IORESOURCE_MEM_64;
+                               }
+                       }
                        break;
                }
        }

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