ACPI: PCI: Clear _DEP dependencies after PCI root bridge attach

PCI root bridges enumerated by acpi_pci_root_add() can be the _DEP
supplier for other ACPI consumers, most notably ACPI0017 CXL root
devices whose probe path depends on acpi_pci_find_root() succeeding.
Once the root bus has been added, those consumers can safely be
enumerated, so notify them by clearing the dependency.

Call acpi_dev_clear_dependencies() at the end of acpi_pci_root_add(),
after pci_bus_add_devices(), following the same pattern used by other
ACPI suppliers such as the EC (drivers/acpi/ec.c) and the ACPI PCI
Link device (drivers/acpi/pci_link.c). The clear is intentionally
done only on the success path; on the error paths the supplier did
not attach and consumers must keep dep_unmet set.

This is a prerequisite for honoring _DEP on ACPI0016 host bridges,
which matters on architectures where the probe order of acpi_pci_root
relative to cxl_acpi is not guaranteed (e.g. RISC-V).

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
Suggested-by: Dan Williams (nvidia) <djbw@kernel.org>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20260526025118.38935-2-cp0613@linux.alibaba.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index a0ba64e45e8ab3633cc8a98e43c32cc9139dca76..4c06c3ffd0cbb54373cf1ba7d47d24251df90772 100644 (file)
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -755,6 +755,10 @@ static int acpi_pci_root_add(struct acpi_device *device,
        pci_lock_rescan_remove();
        pci_bus_add_devices(root->bus);
        pci_unlock_rescan_remove();
+
+       /* Clear _DEP dependencies to allow consumers to enumerate */
+       acpi_dev_clear_dependencies(device);
+
        return 1;
 
 remove_dmar: