linux-kernel - [PATCH 09/15] cxl/acpi: Determine PCI host bridge's ACPI UID

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Date:   Wed, 31 Aug 2022 10:15:57 +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 09/15] cxl/acpi: Determine PCI host bridge's ACPI UID

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@....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))
+			continue;
+
+		dev_dbg(&adev->dev, "host uid: %llu\n", uid);
+
+		if (uid > U32_MAX)
+			continue;
+
 		dev_info(&host->dev, "host supports CXL\n");
 	}
 
-- 
2.30.2