tree 88e0ee1c1fae6b186cda16b4ee476a72f98b90b9
parent d31cbc74d1317aa5beb8619d93b9337d2c1370de
author Arthur Heymans <arthur@aheymans.xyz> 1686230547 +0200
committer Lean Sheng Tan <sheng.tan@9elements.com> 1689849522 +0000

acpi: Move ECAM resource below PNP0C02 device in a common place

From the Linux documentation (Documentation/PCI/acpi-info.rst):
[6] PCI Firmware 3.2, sec 4.1.2:
    If the operating system does not natively comprehend reserving the
    MMCFG region, the MMCFG region must be reserved by firmware.  The
    address range reported in the MCFG table or by _CBA method (see Section
    4.1.3) must be reserved by declaring a motherboard resource.  For most
    systems, the motherboard resource would appear at the root of the ACPI
    namespace (under \_SB) in a node with a _HID of EISAID (PNP0C02), and
    the resources in this case should not be claimed in the root PCI bus’s
    _CRS.  The resources can optionally be returned in Int15 E820 or
    EFIGetMemoryMap as reserved memory but must always be reported through
    ACPI as a motherboard resource.

So in order for the OS to use ECAM MMCONF over legacy PCI IO
configuration, a PNP0C02 HID device needs to reserve this region.

As no AMD platform has this defined in DSDT this fixes Linux using
legacy PCI IO configuration over MMCONF. Tianocore messes with e820
table in such a way that it prevents Linux from using PCIe ECAM. This
change fixes that problem.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: I852e393726a1b086cf582f4d2d707e7cde05cbf4
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75729
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Sean Rhodes <sean@starlabs.systems>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>