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    SubjectRE: [PATCH 05/15] cxl/acpi: Add probe function to detect restricted CXL hosts in RCD mode
    Robert Richter wrote:
    > Restricted CXL device (RCD) mode (formerly CXL 1.1) uses a different
    > enumeration scheme other than CXL VH (formerly CXL 2.0). In RCD mode a
    > host/device (RCH-RCD) pair shows up as a legal PCIe hierarchy with an
    > ACPI host bridge ("PNP0A08" or "ACPI0016" HID) and RCiEP connected to
    > it with a description of the CXL device.
    >
    > Add function cxl_restricted_host_probe() to probe RCD enumerated
    > devices. The function implements a loop that detects all CXL capable
    > ACPI PCI root bridges in the system (RCD mode only). The iterator
    > function cxl_find_next_rch() is introduced to walk through all of the
    > CXL hosts. The loop will then enable all CXL devices connected to the
    > host. For now, only implement an empty loop with an iterator that
    > returns all pci host bridges in the system.
    >
    > The probe function is triggered by adding an own root device for RCHs.
    > This is different to CXL VH where an ACPI "ACPI0017" root device
    > exists. Its detection starts the CXL host detection. In RCD mode such
    > a device does not necessarily exists, so solve this by creating a
    > plain platform device that is not an ACPI device and is root only for
    > RCHs.

    These host bridges should be discovered by add_host_bridge_dport(), no?
    Unless the BIOS is failing to emit the expected CEDT along with
    ACPI0017.

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