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

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Message-ID: <20220831081603.3415-9-rrichter@amd.com>
Date:   Wed, 31 Aug 2022 10:15:56 +0200
From:   Robert Richter <rrichter@....com>
To:     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: [PATCH 08/15] cxl/acpi: Check RCH's CXL DVSEC capabilities

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);
+		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;
-- 
2.30.2