Messages in this thread | | | Date | Thu, 8 Sep 2022 14:10:00 -0700 | From | Dan Williams <> | Subject | Re: [PATCH 09/15] cxl/acpi: Determine PCI host bridge's ACPI UID |
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Jonathan Zhang (Infra) wrote: > > > > On Aug 31, 2022, at 1:15 AM, Robert Richter <rrichter@amd.com> wrote: > > > > The UID is needed to read the RCH's CEDT entry with the RCRB base > > address. Determine the host's UID from its ACPI fw node. > > > > Signed-off-by: Robert Richter <rrichter@amd.com> > > --- > > drivers/cxl/acpi.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > > index f9cdf23a91a8..b3146b7ae922 100644 > > --- a/drivers/cxl/acpi.c > > +++ b/drivers/cxl/acpi.c > > @@ -368,8 +368,20 @@ struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host) > > static int __init cxl_restricted_host_probe(struct platform_device *pdev) > > { > > struct pci_host_bridge *host = NULL; > > + struct acpi_device *adev; > > + unsigned long long uid = ~0; > > > > while ((host = cxl_find_next_rch(host)) != NULL) { > > + adev = ACPI_COMPANION(&host->dev); > > + if (!adev || !adev->pnp.unique_id || > > + (kstrtoull(adev->pnp.unique_id, 10, &uid) < 0)) > The UID field holds 4 bytes of ASCII characters. kstrtoull() would fail > if the UID field has value such as ‘CX03’.
The UID field is not 4 ASCII characters.
We went through this before in the original code in drivers/cxl/acpi.c::add_host_bridge_dport().
The CEDT.CHBS defines _UID as an integer so use acpi_evaluate_integer() to retrieve the UID to perform the comparison. I thought there was an errata filed to clarify this, but it seems the current spec still just says "value". The CFMWS also places _UID values in the target list, those are also handled as integers.
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