Re: [PATCH 1/1] cxl/acpi.c: Add buggy BIOS hint for CXL ACPI lookup failure

Bjorn Helgaas
2024-04-09T13:22:43Z

On Sun, Apr 07, 2024 at 02:05:26PM -0700, ppwaskie@kernel.org wrote:
> From: PJ Waskiewicz <ppwaskie@kernel.org>
>
> Currently, Type 3 CXL devices (CXL.mem) can train using host CXL
> drivers on Emerald Rapids systems. However, on some production
> systems from some vendors, a buggy BIOS exists that improperly
> populates the ACPI => PCI mappings.

Can you be more specific about what this ACPI => PCI mapping is?
If you already know what the problem is, I'm sure this is obvious, but
otherwise it's not.

> This leads to the cxl_acpi
> driver to fail probe when it cannot find the root port's _UID, in
> order to look up the device's CXL attributes in the CEDT.
>
> Add a bit more of a descriptive message that the lookup failure
> could be a bad BIOS, rather than just "failed."
>
> Signed-off-by: PJ Waskiewicz <ppwaskie@kernel.org>
> ---
> drivers/cxl/acpi.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index af5cb818f84d..56019466a09c 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -504,7 +504,7 @@ static int cxl_get_chbs(struct device *dev, struct acpi_device *hb,
>
> rc = acpi_evaluate_integer(hb->handle, METHOD_NAME__UID, NULL, &uid);
> if (rc != AE_OK) {
> - dev_err(dev, "unable to retrieve _UID\n");
> + dev_err(dev, "unable to retrieve _UID. Potentially buggy BIOS\n");
> return -ENOENT;
> }
>
> --
> 2.40.1
>