On Fri, May 31, 2024 at 12:14:18PM -0400, Frank Li wrote:

On Thu, May 30, 2024 at 06:08:32PM -0500, Bjorn Helgaas wrote:

quoted

On Tue, May 28, 2024 at 03:39:21PM -0400, Frank Li wrote:

quoted

For the i.MX95, configuration of a LUT is necessary to convert Bus Device
Function (BDF) to stream IDs, which are utilized by both IOMMU and ITS.
This involves examining the msi-map and smmu-map to ensure consistent
mapping of PCI BDF to the same stream IDs. Subsequently, LUT-related
registers are configured. In the absence of an msi-map, the built-in MSI
controller is utilized as a fallback.

Additionally, register a PCI bus notifier to trigger imx_pcie_add_device()
upon the appearance of a new PCI device and when the bus is an iMX6 PCI
controller. This function configures the correct LUT based on Device Tree
Settings (DTS).

This scheme is pretty similar to apple_pcie_bus_notifier().  If we
have to do this, I wish it were *more* similar, i.e., copy the
function names, bitmap tracking, code structure, etc.

Actually, I refer apple_pcie_bus_notifier(). I can't direct use apple's
implement because in imx95 have difference PCI host controller, another one
is PCI ECAM netc controller. At lease function name should be similar with
apple. 

I know it's different hardware, so obviously it can't be exactly the
same.  These are the differences that looked possibly unnecessary:

  - registering from initcall instead of .probe():

      apple_pcie_probe                  # .probe() method
        bus_register_notifier(&pci_bus_type, &apple_pcie_nb)

      imx_pcie_init                     # device_initcall()
        bus_register_notifier(&pci_bus_type, &imx_pcie_nb)

  - naming BUS_NOTIFY_DEL_DEVICE function:

      apple_pcie_release_device()
      imx_pcie_del_device()

  - tracking entries in use via bitmap vs scanning hardware for
    invalid entries:

      bitmap_find_free_region           # apple

      imx_pcie_config_lut               # imx
        for (i = 0; i < IMX95_MAX_LUT; i++)
          regmap_read(imx_pcie->iomuxc_gpr, IMX95_PE0_LUT_DATA1, &data1)
          if (data1 & IMX95_PE0_LUT_VLD)
            continue

When we fix a bug in one driver, it's easier to check whether other
drivers also need the fix if they use the same structure and names.

Bjorn

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