Re: [PATCH v2 1/4] PCI: of: Override 64-bit flag for non-prefetchable memory below 4GB
From: Ard Biesheuvel <ardb@kernel.org>
Date: 2021-06-01 05:49:21
Also in:
linux-pci, linux-rockchip, lkml
Hi Punit, On Tue, 1 Jun 2021 at 00:11, Punit Agrawal [off-list ref] wrote:
Some host bridges advertise non-prefetable memory windows that are
typo ^
entirely located below 4GB but are marked as 64-bit address memory.
Since commit 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource
flags for 64-bit memory addresses"), the OF PCI range parser takes a
stricter view and treats 64-bit address ranges as advertised while
before such ranges were treated as 32-bit.
A PCI host bridge that is modelled as PCI-to-PCI bridge cannot forwardIt is the root port which is modeled as a P2P bridge. The root port(s) together with the host bridge is what makes up the root complex.
64-bit non-prefetchable memory ranges. As a result, the change in behaviour due to the commit causes allocation failure for devices that require non-prefetchable bus addresses.
AIUI, the problem is not that the device requires a non-prefetchable bus address, but that it fails to allocate a 32-bit BAR from a 64-bit non-prefetchable window.
quoted hunk ↗ jump to hunk
In order to not break platforms, override the 64-bit flag for non-prefetchable memory ranges that lie entirely below 4GB. Suggested-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/7a1e2ebc-f7d8-8431-d844-41a9c36a8911@arm.com (local) Signed-off-by: Punit Agrawal <redacted> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Rob Herring <robh+dt@kernel.org> Signed-off-by: Punit Agrawal <redacted> --- drivers/pci/of.c | 8 ++++++++ 1 file changed, 8 insertions(+)diff --git a/drivers/pci/of.c b/drivers/pci/of.c index da5b414d585a..e2e64c5c55cb 100644 --- a/drivers/pci/of.c +++ b/drivers/pci/of.c@@ -346,6 +346,14 @@ static int devm_of_pci_get_host_bridge_resources(struct device *dev, dev_warn(dev, "More than one I/O resource converted for %pOF. CPU base address for old range lost!\n", dev_node); *io_base = range.cpu_addr; + } else if (resource_type(res) == IORESOURCE_MEM) { + if (!(res->flags & IORESOURCE_PREFETCH)) { + if (res->flags & IORESOURCE_MEM_64) + if (!upper_32_bits(range.pci_addr + range.size - 1)) { + dev_warn(dev, "Clearing 64-bit flag for non-prefetchable memory below 4GB\n"); + res->flags &= ~IORESOURCE_MEM_64; + } + } } pci_add_resource_offset(resources, res, res->start - range.pci_addr); --2.30.2
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