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

PJ Waskiewicz
2024-04-08T02:03:25Z

On 24/04/07 11:28PM, Lukas Wunner wrote:

Hi Lukas,

> On Sun, Apr 07, 2024 at 02:05:26PM -0700, ppwaskie@kernel.org wrote:
> > --- 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;
> > }
>
> dev_err(dev, FW_BUG "unable to retrieve _UID\n");
> ^^^^^^
>
> There's a macro for that.

Doh...it's been awhile since I've crossed buggy BIOS's. Thanks for the
review and comment.

Updated patch:

cxl/acpi.c: Add buggy BIOS hint for CXL ACPI lookup failure

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. 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."

v2: Updated message to use existing FW_BUG macro

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..d321cfbd4682 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, FW_BUG "unable to retrieve _UID\n");
return -ENOENT;
}

--
2.40.1