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SubjectRe: [PATCH 08/15] cxl/acpi: Check RCH's CXL DVSEC capabilities
On Wed, 31 Aug 2022 10:15:56 +0200
Robert Richter <rrichter@amd.com> wrote:

> An RCH has an RCiEP connected to it with CXL DVSEC capabilities
> present and the CXL PCIe DVSEC included. Check this.
>
> Signed-off-by: Robert Richter <rrichter@amd.com>
One comment inline. This looks good to me.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
> drivers/cxl/acpi.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index ffdf439adb87..f9cdf23a91a8 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -322,6 +322,8 @@ struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host)
> {
> struct pci_bus *bus = host ? host->bus : NULL;
> struct acpi_device *adev;
> + struct pci_dev *pdev;
> + bool is_restricted_host;
>
> while ((bus = pci_find_next_bus(bus)) != NULL) {
> host = bus ? to_pci_host_bridge(bus->bridge) : NULL;
> @@ -343,6 +345,20 @@ struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host)
> dev_dbg(&host->dev, "PCI ACPI host found: %s\n",
> acpi_dev_name(adev));
>
> + /* Check CXL DVSEC of dev 0 func 0 */

So assumption here is that the hostbridge has a one or more RCiEPs.
The spec (r3.0 9.11.4) allows for the EP to appear behind a root port
- that case always felt odd to me, so I'm fine with not supporting it until
we see a user.

> + pdev = pci_get_slot(bus, PCI_DEVFN(0, 0));
> + is_restricted_host = pdev
> + && (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END)
> + && pci_find_dvsec_capability(pdev,
> + PCI_DVSEC_VENDOR_ID_CXL,
> + CXL_DVSEC_PCIE_DEVICE);
> + pci_dev_put(pdev);
> +
> + if (!is_restricted_host)
> + continue;
> +
> + dev_dbg(&host->dev, "CXL restricted host found\n");
> +
> return host;
> }
>
> @@ -354,6 +370,7 @@ static int __init cxl_restricted_host_probe(struct platform_device *pdev)
> struct pci_host_bridge *host = NULL;
>
> while ((host = cxl_find_next_rch(host)) != NULL) {
> + dev_info(&host->dev, "host supports CXL\n");
> }
>
> return 0;

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