cxl/core: Refactor CXL register lookup for bridge reuse

While CXL Memory Device endpoints locate the CXL MMIO registers in a PCI
BAR, CXL root bridges have their MMIO base address described by platform
firmware. Refactor the existing register lookup into a generic facility
for endpoints and bridges to share.
Reviewed-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162096972534.1865304.3218686216153688039.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core.c

 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright(c) 2020 Intel Corporation. All rights reserved. */
+#include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/device.h>
 #include <linux/module.h>
+#include "cxl.h"
 
 /**
  * DOC: cxl core
@@ -10,6 +12,61 @@
  * point for cross-device interleave coordination through cxl ports.
  */
 
+/**
+ * cxl_setup_device_regs() - Detect CXL Device register blocks
+ * @dev: Host device of the @base mapping
+ * @base: Mapping of CXL 2.0 8.2.8 CXL Device Register Interface
+ * @regs: Base pointers for device register blocks (see CXL_DEVICE_REGS())
+ */
+void cxl_setup_device_regs(struct device *dev, void __iomem *base,
+			   struct cxl_device_regs *regs)
+{
+	int cap, cap_count;
+	u64 cap_array;
+
+	*regs = (struct cxl_device_regs) { 0 };
+
+	cap_array = readq(base + CXLDEV_CAP_ARRAY_OFFSET);
+	if (FIELD_GET(CXLDEV_CAP_ARRAY_ID_MASK, cap_array) !=
+	    CXLDEV_CAP_ARRAY_CAP_ID)
+		return;
+
+	cap_count = FIELD_GET(CXLDEV_CAP_ARRAY_COUNT_MASK, cap_array);
+
+	for (cap = 1; cap <= cap_count; cap++) {
+		void __iomem *register_block;
+		u32 offset;
+		u16 cap_id;
+
+		cap_id = FIELD_GET(CXLDEV_CAP_HDR_CAP_ID_MASK,
+				   readl(base + cap * 0x10));
+		offset = readl(base + cap * 0x10 + 0x4);
+		register_block = base + offset;
+
+		switch (cap_id) {
+		case CXLDEV_CAP_CAP_ID_DEVICE_STATUS:
+			dev_dbg(dev, "found Status capability (0x%x)\n", offset);
+			regs->status = register_block;
+			break;
+		case CXLDEV_CAP_CAP_ID_PRIMARY_MAILBOX:
+			dev_dbg(dev, "found Mailbox capability (0x%x)\n", offset);
+			regs->mbox = register_block;
+			break;
+		case CXLDEV_CAP_CAP_ID_SECONDARY_MAILBOX:
+			dev_dbg(dev, "found Secondary Mailbox capability (0x%x)\n", offset);
+			break;
+		case CXLDEV_CAP_CAP_ID_MEMDEV:
+			dev_dbg(dev, "found Memory Device capability (0x%x)\n", offset);
+			regs->memdev = register_block;
+			break;
+		default:
+			dev_dbg(dev, "Unknown cap ID: %d (0x%x)\n", cap_id, offset);
+			break;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(cxl_setup_device_regs);
+
 struct bus_type cxl_bus_type = {
 	.name = "cxl",
 };

drivers/cxl/cxl.h

@@ -66,5 +66,8 @@ struct cxl_regs {
 	};
 };
 
+void cxl_setup_device_regs(struct device *dev, void __iomem *base,
+			   struct cxl_device_regs *regs);
+
 extern struct bus_type cxl_bus_type;
 #endif /* __CXL_H__ */

drivers/cxl/mem.c

@@ -884,53 +884,15 @@ static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, u16 opcode,
 static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
 {
 	struct device *dev = &cxlm->pdev->dev;
-	int cap, cap_count;
-	u64 cap_array;
+	struct cxl_regs *regs = &cxlm->regs;
 
-	cap_array = readq(cxlm->base + CXLDEV_CAP_ARRAY_OFFSET);
-	if (FIELD_GET(CXLDEV_CAP_ARRAY_ID_MASK, cap_array) !=
-	    CXLDEV_CAP_ARRAY_CAP_ID)
-		return -ENODEV;
-
-	cap_count = FIELD_GET(CXLDEV_CAP_ARRAY_COUNT_MASK, cap_array);
-
-	for (cap = 1; cap <= cap_count; cap++) {
-		void __iomem *register_block;
-		u32 offset;
-		u16 cap_id;
-
-		cap_id = FIELD_GET(CXLDEV_CAP_HDR_CAP_ID_MASK,
-				   readl(cxlm->base + cap * 0x10));
-		offset = readl(cxlm->base + cap * 0x10 + 0x4);
-		register_block = cxlm->base + offset;
-
-		switch (cap_id) {
-		case CXLDEV_CAP_CAP_ID_DEVICE_STATUS:
-			dev_dbg(dev, "found Status capability (0x%x)\n", offset);
-			cxlm->regs.status = register_block;
-			break;
-		case CXLDEV_CAP_CAP_ID_PRIMARY_MAILBOX:
-			dev_dbg(dev, "found Mailbox capability (0x%x)\n", offset);
-			cxlm->regs.mbox = register_block;
-			break;
-		case CXLDEV_CAP_CAP_ID_SECONDARY_MAILBOX:
-			dev_dbg(dev, "found Secondary Mailbox capability (0x%x)\n", offset);
-			break;
-		case CXLDEV_CAP_CAP_ID_MEMDEV:
-			dev_dbg(dev, "found Memory Device capability (0x%x)\n", offset);
-			cxlm->regs.memdev = register_block;
-			break;
-		default:
-			dev_dbg(dev, "Unknown cap ID: %d (0x%x)\n", cap_id, offset);
-			break;
-		}
-	}
+	cxl_setup_device_regs(dev, cxlm->base, &regs->device_regs);
 
-	if (!cxlm->regs.status || !cxlm->regs.mbox || !cxlm->regs.memdev) {
+	if (!regs->status || !regs->mbox || !regs->memdev) {
 		dev_err(dev, "registers not found: %s%s%s\n",
-			!cxlm->regs.status ? "status " : "",
-			!cxlm->regs.mbox ? "mbox " : "",
-			!cxlm->regs.memdev ? "memdev" : "");
+			!regs->status ? "status " : "",
+			!regs->mbox ? "mbox " : "",
+			!regs->memdev ? "memdev" : "");
 		return -ENXIO;
 	}