linux-kernel - [PATCH v4] PCI: of: Clear 64-bit flag for non-prefetchable memory below 4GB

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Message-Id: <20210614230457.752811-1-punitagrawal@gmail.com>
Date:   Tue, 15 Jun 2021 08:04:57 +0900
From:   Punit Agrawal <punitagrawal@...il.com>
To:     helgaas@...nel.org, robh+dt@...nel.org
Cc:     Punit Agrawal <punitagrawal@...il.com>, maz@...nel.org,
        leobras.c@...il.com, linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, alexandru.elisei@....com, wqu@...e.com,
        robin.murphy@....com, pgwipeout@...il.com, ardb@...nel.org,
        briannorris@...omium.org, shawn.lin@...k-chips.com,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH v4] PCI: of: Clear 64-bit flag for non-prefetchable memory below 4GB

Alexandru and Qu reported this resource allocation failure on
ROCKPro64 v2 and ROCK Pi 4B, both based on the RK3399:

  pci_bus 0000:00: root bus resource [mem 0xfa000000-0xfbdfffff 64bit]
  pci 0000:00:00.0: PCI bridge to [bus 01]
  pci 0000:00:00.0: BAR 14: no space for [mem size 0x00100000]
  pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x00003fff 64bit]

"BAR 14" is the PCI bridge's 32-bit non-prefetchable window, and our
PCI allocation code isn't smart enough to allocate it in a host
bridge window marked as 64-bit, even though this should work fine.

A DT host bridge description includes the windows from the CPU
address space to the PCI bus space.  On a few architectures
(microblaze, powerpc, sparc), the DT may also describe PCI devices
themselves, including their BARs.

Before 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource
flags for 64-bit memory addresses"), of_bus_pci_get_flags() ignored
the fact that some DT addresses described 64-bit windows and BARs.
That was a problem because the virtio virtual NIC has a 32-bit BAR
and a 64-bit BAR, and the driver couldn't distinguish them.

9d57e61bf723 set IORESOURCE_MEM_64 for those 64-bit DT ranges, which
fixed the virtio driver.  But it also set IORESOURCE_MEM_64 for host
bridge windows, which exposed the fact that the PCI allocator isn't
smart enough to put 32-bit resources in those 64-bit windows.

Clear IORESOURCE_MEM_64 from host bridge windows since we don't need
that information.

Fixes: 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource flags for 64-bit memory addresses")
Reported-at: https://lore.kernel.org/lkml/7a1e2ebc-f7d8-8431-d844-41a9c36a8911@arm.com/
Reported-by: Alexandru Elisei <alexandru.elisei@....com>
Reported-by: Qu Wenruo <wqu@...e.com>
Suggested-by: Bjorn Helgaas <bhelgaas@...gle.com>
Signed-off-by: Punit Agrawal <punitagrawal@...il.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Rob Herring <robh+dt@...nel.org>
---
Hi,

The patch is an updated version to fix the PCI allocation issues on
RK3399 based platforms. Previous postings can be found at [0][1][2].

The updated patch instead of clearing the 64-bit flag for
non-prefetchable memory below 4GB does it unconditionally on the basis
that PCI allocation logic cannot deal with the 64-bit flag (although
it should be able to). The result is a simpler patch that restores the
input to the allocation logic to be identical to before 9d57e61bf723.

Tested locally on a RockPro64 on top of v5.13-rc6. Please consider
merging.

Thanks,
Punit

Changes:
v4:

* Updated Patch 1 based on Bjorn's suggestion. Also dropped the
  Tested-by tags due to the change of logic
* Dropped patch 2 and 3 from the series as it's not critical to the
  series
* Dropped the device tree changes (Patch 4) as they are already queued
  in the soc tree

v3:
* Improved commit log for clarity (Patch 1)
* Added Tested-by tags

v2:
* Check ranges PCI / bus addresses rather than CPU addresses
* (new) Restrict 32-bit size warnings on ranges that don't have the 64-bit attribute set
* Refactor the 32-bit size warning to the range parsing loop. This
  change also prints the warnings right after the window mappings are
  logged.

[0] https://lore.kernel.org/linux-arm-kernel/20210527150541.3130505-1-punitagrawal@gmail.com/
[1] https://lore.kernel.org/linux-pci/20210531221057.3406958-1-punitagrawal@gmail.com/
[2] https://lore.kernel.org/linux-pci/20210607112856.3499682-1-punitagrawal@gmail.com/

 drivers/pci/of.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 85dcb7097da4..a143b02b2dcd 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -353,6 +353,8 @@ 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) {
+			res->flags &= ~IORESOURCE_MEM_64;
 		}

 		pci_add_resource_offset(resources, res,	res->start - range.pci_addr);
-- 
2.30.2