ACPI: scan: Honor _DEP for ACPI0016 PCI/CXL host bridge

CXL root devices (ACPI0017) declare _DEP on their parent ACPI0016
PCI/CXL host bridge so that cxl_acpi probes only after acpi_pci_root
has attached the PCI root and registered it for acpi_pci_find_root().
However, acpi_dev_ready_for_enumeration() only consults dep_unmet
when the supplier's HID is on acpi_honor_dep_ids[]; otherwise the
dependency is silently ignored.

Without honoring the dependency, cxl_acpi can probe before the PCI
root is ready. The resulting CXL topology is broken: decoder targets
read as 0 and no port/endpoint devices appear under
/sys/bus/cxl/devices/.

Add ACPI0016 to acpi_honor_dep_ids[] so the _DEP declared by ACPI0017
is enforced. This relies on the preceding patch ("ACPI: PCI: clear
_DEP dependencies after PCI root bridge attach"), which releases the
dependency once the PCI root is fully enumerated; the two patches
must be applied together.

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20260526025118.38935-3-cp0613@linux.alibaba.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 530547cda8b2866ad1aa39dc3a26a66d8ffa3df1..5f20e7748f3642bfccd646c8fa246efd5e4e596a 100644 (file)
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -866,6 +866,7 @@ static const char * const acpi_honor_dep_ids[] = {
        "RSCV0005", /* RISC-V SBI MPXY MBOX */
        "RSCV0006", /* RISC-V RPMI SYSMSI */
        "PNP0C0F",  /* PCI Link Device */
+       "ACPI0016", /* CXL/PCIe host bridge: CXL root (ACPI0017) depends on PCI root attach */
        NULL
 };