linux-kernel - RE: [PATCH 08/15] cxl/acpi: Check RCH's CXL DVSEC capabilities

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Date:   Wed, 7 Sep 2022 23:18:03 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Robert Richter <rrichter@....com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Ira Weiny" <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        "Dan Williams" <dan.j.williams@...el.com>
CC:     <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, Robert Richter <rrichter@....com>
Subject: RE: [PATCH 08/15] cxl/acpi: Check RCH's CXL DVSEC capabilities

Robert Richter 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@....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 */
> +		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);

The check looks good, just the matter of integrating it into the
existing ACPI0016 device detection.