In subject, this or similar would match history:
PCI/ACPI: Add Broadcom bcm2711 MCFG quirk
On Thu, Aug 05, 2021 at 04:12:00PM -0500, Jeremy Linton wrote:
> Now that we have a bcm2711 quirk, we need to be able to
> detect it when the MCFG is missing. Use a namespace
> property as an alternative to the MCFG OEM.
Rewrap to use ~75 columns.
Mention the DT namespace property here.
> Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> ---
> drivers/acpi/pci_mcfg.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
> index 53cab975f612..7d77fc72c2a4 100644
> --- a/drivers/acpi/pci_mcfg.c
> +++ b/drivers/acpi/pci_mcfg.c
> @@ -169,6 +169,9 @@ static struct mcfg_fixup mcfg_quirks[] = {
> ALTRA_ECAM_QUIRK(1, 13),
> ALTRA_ECAM_QUIRK(1, 14),
> ALTRA_ECAM_QUIRK(1, 15),
> +
> + { "bcm2711", "", 0, 0, MCFG_BUS_ANY, &bcm2711_pcie_ops,
> + DEFINE_RES_MEM(0xFD500000, 0xA000) },
> };
>
> static char mcfg_oem_id[ACPI_OEM_ID_SIZE];
> @@ -198,8 +201,19 @@ static void pci_mcfg_apply_quirks(struct acpi_pci_root *root,
> u16 segment = root->segment;
> struct resource *bus_range = &root->secondary;
> struct mcfg_fixup *f;
> + const char *soc;
> int i;
>
> + /*
> + * This could be a machine with a PCI/SMC conduit,
> + * which means it doens't have MCFG. Get the machineid from
> + * the namespace definition instead.
s/SMC/SMCCC/ ? Cover letter uses SMCCC (not sure it's relevant anyway)
s/doens't/doesn't/
Rewrap comment to use ~80 columns.
Seems pretty reasonable that a platform without standard ECAM might
not have MCFG, since MCFG basically implies ECAM.
Is "linux,pcie-quirk" the right property to look for? It doesn't
sound very generic, and it doesn't sound like anything related to
ECAM. Is it new? I don't see it in the tree yet. Should it be in
Documentation/devicetree/bindings/pci/pci.txt so we don't get a
different property name for every new platform?
> + */
> + if (!fwnode_property_read_string(acpi_fwnode_handle(root->device),
> + "linux,pcie-quirk", &soc)) {
> + memcpy(mcfg_oem_id, soc, ACPI_OEM_ID_SIZE);
> + }
> +
> for (i = 0, f = mcfg_quirks; i < ARRAY_SIZE(mcfg_quirks); i++, f++) {
> if (pci_mcfg_quirk_matches(f, segment, bus_range)) {
> if (f->cfgres.start)
> --
> 2.31.1
>
