On Tue, May 26, 2020 at 07:49:07PM +0800, Zhangfei Gao wrote:

Some platform devices appear as PCI but are actually on the AMBA bus,
and they need fixup in drivers/pci/quirks.c handling iommu_fwnode.
Here introducing PCI_FIXUP_IOMMU, which is called after iommu_fwnode
is allocated, instead of reusing PCI_FIXUP_FINAL since it will slow
down iommu probing as all devices in fixup final list will be
reprocessed, suggested by Joerg, [1]

Is this slowdown significant?  We already iterate over every device
when applying PCI_FIXUP_FINAL quirks, so if we used the existing
PCI_FIXUP_FINAL, we wouldn't be adding a new loop.  We would only be
adding two more iterations to the loop in pci_do_fixups() that tries
to match quirks against the current device.  I doubt that would be a
measurable slowdown.

For example:
Hisilicon platform device need fixup in
drivers/pci/quirks.c handling fwspec->can_stall, which is introduced in [2]

+static void quirk_huawei_pcie_sva(struct pci_dev *pdev)
+{
+    struct iommu_fwspec *fwspec;
+
+    pdev->eetlp_prefix_path = 1;
+    fwspec = dev_iommu_fwspec_get(&pdev->dev);
+    if (fwspec)
+        fwspec->can_stall = 1;
+}
+
+DECLARE_PCI_FIXUP_IOMMU(PCI_VENDOR_ID_HUAWEI, 0xa250, quirk_huawei_pcie_sva);
+DECLARE_PCI_iFIXUP_IOMMU(PCI_VENDOR_ID_HUAWEI, 0xa251, quirk_huawei_pcie_sva); 

[1] https://www.spinics.net/lists/iommu/msg44591.html
[2] https://www.spinics.net/lists/linux-pci/msg94559.html

If you reference these in the commit logs, please use lore.kernel.org
links instead of spinics.

Zhangfei Gao (2):
  PCI: Introduce PCI_FIXUP_IOMMU
  iommu: calling pci_fixup_iommu in iommu_fwspec_init

 drivers/iommu/iommu.c             | 4 ++++
 drivers/pci/quirks.c              | 7 +++++++
 include/asm-generic/vmlinux.lds.h | 3 +++
 include/linux/pci.h               | 8 ++++++++
 4 files changed, 22 insertions(+)

-- 
2.7.4

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