On Tue, 24 Aug 2021 09:07:28 -0700 Dan Williams dan.j.williams@intel.com wrote:
From: Alison Schofield alison.schofield@intel.com
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 dan.j.williams@intel.com Signed-off-by: Alison Schofield alison.schofield@intel.com Fixes: 7d4b5ca2e2cb ("cxl/acpi: Add downstream port data to cxl_port instances") Cc: stable@vger.kernel.org Signed-off-by: Dan Williams dan.j.williams@intel.com
I'd imagine we want to get this in an early rc so perhaps pull out of this series.
Reviewed-by: Jonathan Cameron Jonathan.Cameron@huawei.com
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,