On Tue, 24 Aug 2021 09:07:28 -0700 Dan Williams <[email protected]> wrote:
> From: Alison Schofield <[email protected]> > > During CXL ACPI probe, host bridge ports are discovered by scanning > the ACPI0017 root port for ACPI0016 host bridge devices. The scan > matches on the hardware id of "ACPI0016". An issue occurs when an > ACPI0016 device is defined in the DSDT yet disabled on the platform. > Attempts by the cxl_acpi driver to add host bridge ports using a > disabled device fails, and the entire cxl_acpi probe fails. > > The DSDT table includes an _STA method that sets the status and the > ACPI subsystem has checks available to examine it. One such check is > in the acpi_pci_find_root() path. Move the call to acpi_pci_find_root() > to the matching function to prevent this issue when adding either > upstream or downstream ports. You could mention that has the side effect that the existing call in add_host_bridge_uport() is now guarantee not to fail so can be moved closer to where it is used. That chunk had me briefly confused. > > Suggested-by: Dan Williams <[email protected]> > Signed-off-by: Alison Schofield <[email protected]> > Fixes: 7d4b5ca2e2cb ("cxl/acpi: Add downstream port data to cxl_port > instances") > Cc: <[email protected]> > Signed-off-by: Dan Williams <[email protected]> I'd imagine we want to get this in an early rc so perhaps pull out of this series. Reviewed-by: Jonathan Cameron <[email protected]> > --- > drivers/cxl/acpi.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > index 8ae89273f58e..2d8f1ec1abff 100644 > --- a/drivers/cxl/acpi.c > +++ b/drivers/cxl/acpi.c > @@ -243,6 +243,9 @@ static struct acpi_device *to_cxl_host_bridge(struct > device *dev) > { > struct acpi_device *adev = to_acpi_device(dev); > > + if (!acpi_pci_find_root(adev->handle)) > + return NULL; > + > if (strcmp(acpi_device_hid(adev), "ACPI0016") == 0) > return adev; > return NULL; > @@ -266,10 +269,6 @@ static int add_host_bridge_uport(struct device *match, > void *arg) > if (!bridge) > return 0; > > - pci_root = acpi_pci_find_root(bridge->handle); > - if (!pci_root) > - return -ENXIO; > - > dport = find_dport_by_dev(root_port, match); > if (!dport) { > dev_dbg(host, "host bridge expected and not found\n"); > @@ -282,6 +281,7 @@ static int add_host_bridge_uport(struct device *match, > void *arg) > return PTR_ERR(port); > dev_dbg(host, "%s: add: %s\n", dev_name(match), dev_name(&port->dev)); > > + pci_root = acpi_pci_find_root(bridge->handle); > ctx = (struct cxl_walk_context){ > .dev = host, > .root = pci_root->bus, >
