On Tue, 24 Aug 2021 09:07:28 -0700
Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> From: Alison Schofield <alison.schofield@xxxxxxxxx>
>
> 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@xxxxxxxxx>
> Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
> Fixes: 7d4b5ca2e2cb ("cxl/acpi: Add downstream port data to cxl_port instances")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
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@xxxxxxxxxx>
> ---
> 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,
>
