[RFC PATCH 4/9] cxl/mem: Map memory device registers

[Ben Widawsky <ben.widawsky@xxxxxxxxx>]

All the necessary bits are initialized in order to find and map the
register space for CXL Memory Devices. This is accomplished by using the
Register Locator DVSEC (CXL 2.0 - 8.1.9.1) to determine which PCI BAR to
use, and how much of an offset from that BAR should be added.

If the memory device registers are found and mapped a new internal data
structure tracking device state is allocated.

Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
---
 drivers/cxl/mem.c | 68 +++++++++++++++++++++++++++++++++++++++++++----
 drivers/cxl/pci.h |  6 +++++
 2 files changed, 69 insertions(+), 5 deletions(-)

diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index aa7d881fa47b..8d9b9ab6c5ea 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -7,9 +7,49 @@
 #include "pci.h"
 
 struct cxl_mem {
+	struct pci_dev *pdev;
 	void __iomem *regs;
 };
 
+static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev, u32 reg_lo, u32 reg_hi)
+{
+	struct device *dev = &pdev->dev;
+	struct cxl_mem *cxlm;
+	void __iomem *regs;
+	u64 offset;
+	u8 bar;
+	int rc;
+
+	offset = ((u64)reg_hi << 32) | (reg_lo & 0xffff0000);
+	bar = reg_lo & 0x7;
+
+	/* Basic sanity check that BAR is big enough */
+	if (pci_resource_len(pdev, bar) < offset) {
+		dev_err(dev, "bar%d: %pr: too small (offset: %#llx)\n",
+				bar, &pdev->resource[bar], (unsigned long long) offset);
+		return ERR_PTR(-ENXIO);
+	}
+
+	rc = pcim_iomap_regions(pdev, 1 << bar, pci_name(pdev));
+	if (rc != 0) {
+		dev_err(dev, "failed to map registers\n");
+		return ERR_PTR(-ENXIO);
+	}
+
+	cxlm = devm_kzalloc(&pdev->dev, sizeof(*cxlm), GFP_KERNEL);
+	if (!cxlm) {
+		dev_err(dev, "No memory available\n");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	regs = pcim_iomap_table(pdev)[bar];
+	cxlm->pdev = pdev;
+	cxlm->regs = regs + offset;
+
+	dev_dbg(dev, "Mapped CXL Memory Device resource\n");
+	return cxlm;
+}
+
 static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
 {
 	int pos;
@@ -34,9 +74,9 @@ static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
 
 static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
+	struct cxl_mem *cxlm = ERR_PTR(-ENXIO);
 	struct device *dev = &pdev->dev;
-	struct cxl_mem *cxlm;
-	int rc, regloc;
+	int rc, regloc, i;
 
 	rc = cxl_bus_prepared(pdev);
 	if (rc != 0) {
@@ -44,15 +84,33 @@ static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 		return rc;
 	}
 
+	rc = pcim_enable_device(pdev);
+	if (rc)
+		return rc;
+
 	regloc = cxl_mem_dvsec(pdev, PCI_DVSEC_ID_CXL_REGLOC);
 	if (!regloc) {
 		dev_err(dev, "register location dvsec not found\n");
 		return -ENXIO;
 	}
+	regloc += 0xc; /* Skip DVSEC + reserved fields */
+
+	for (i = regloc; i < regloc + 0x24; i += 8) {
+		u32 reg_lo, reg_hi;
+
+		pci_read_config_dword(pdev, i, &reg_lo);
+		pci_read_config_dword(pdev, i + 4, &reg_hi);
+
+		if (CXL_REGLOG_IS_MEMDEV(reg_lo)) {
+			cxlm = cxl_mem_create(pdev, reg_lo, reg_hi);
+			break;
+		}
+	}
+
+	if (IS_ERR(cxlm))
+		return -ENXIO;
 
-	cxlm = devm_kzalloc(dev, sizeof(*cxlm), GFP_KERNEL);
-	if (!cxlm)
-		return -ENOMEM;
+	pci_set_drvdata(pdev, cxlm);
 
 	return 0;
 }
diff --git a/drivers/cxl/pci.h b/drivers/cxl/pci.h
index beb03921e6da..be87f62e9132 100644
--- a/drivers/cxl/pci.h
+++ b/drivers/cxl/pci.h
@@ -12,4 +12,10 @@
 #define PCI_DVSEC_ID_CXL	0x0
 #define PCI_DVSEC_ID_CXL_REGLOC	0x8
 
+#define CXL_REGLOG_RBI_EMPTY 0
+#define CXL_REGLOG_RBI_COMPONENT 1
+#define CXL_REGLOG_RBI_VIRT 2
+#define CXL_REGLOG_RBI_MEMDEV 3
+#define CXL_REGLOG_IS_MEMDEV(x) ((((x) >> 8) & 0xff) == CXL_REGLOG_RBI_MEMDEV)
+
 #endif /* __CXL_PCI_H__ */
-- 
2.29.2