cxl/pci: Introduce cxl_decode_register_block()

Each register block located in the DVSEC needs to be decoded from 2
words, 'register offset high' and 'register offset low'.

Create a function, cxl_decode_register_block() to perform this decode
and return the bar, offset, and register type of the register block.

Then use the values decoded in cxl_mem_map_regblock() instead of passing
the raw registers.
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20210528004922.3980613-2-ira.weiny@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/pci.c

@@ -922,17 +922,13 @@ static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev)
 	return cxlm;
 }
 
-static void __iomem *cxl_mem_map_regblock(struct cxl_mem *cxlm, u32 reg_lo, u32 reg_hi)
+static void __iomem *cxl_mem_map_regblock(struct cxl_mem *cxlm,
+					  u8 bar, u64 offset)
 {
 	struct pci_dev *pdev = cxlm->pdev;
 	struct device *dev = &pdev->dev;
-	u64 offset;
-	u8 bar;
 	int rc;
 
-	offset = ((u64)reg_hi << 32) | (reg_lo & CXL_REGLOC_ADDR_MASK);
-	bar = FIELD_GET(CXL_REGLOC_BIR_MASK, reg_lo);
-
 	/* 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,
@@ -974,6 +970,14 @@ static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
 	return 0;
 }
 
+static void cxl_decode_register_block(u32 reg_lo, u32 reg_hi,
+				      u8 *bar, u64 *offset, u8 *reg_type)
+{
+	*offset = ((u64)reg_hi << 32) | (reg_lo & CXL_REGLOC_ADDR_MASK);
+	*bar = FIELD_GET(CXL_REGLOC_BIR_MASK, reg_lo);
+	*reg_type = FIELD_GET(CXL_REGLOC_RBI_MASK, reg_lo);
+}
+
 /**
  * cxl_mem_setup_regs() - Setup necessary MMIO.
  * @cxlm: The CXL memory device to communicate with.
@@ -1009,15 +1013,21 @@ static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
 	for (i = 0; i < regblocks; i++, regloc += 8) {
 		u32 reg_lo, reg_hi;
 		u8 reg_type;
+		u64 offset;
+		u8 bar;
 
 		/* "register low and high" contain other bits */
 		pci_read_config_dword(pdev, regloc, &reg_lo);
 		pci_read_config_dword(pdev, regloc + 4, &reg_hi);
 
-		reg_type = FIELD_GET(CXL_REGLOC_RBI_MASK, reg_lo);
+		cxl_decode_register_block(reg_lo, reg_hi, &bar, &offset,
+					  &reg_type);
+
+		dev_dbg(dev, "Found register block in bar %u @ 0x%llx of type %u\n",
+			bar, offset, reg_type);
 
 		if (reg_type == CXL_REGLOC_RBI_MEMDEV) {
-			base = cxl_mem_map_regblock(cxlm, reg_lo, reg_hi);
+			base = cxl_mem_map_regblock(cxlm, bar, offset);
 			if (IS_ERR(base))
 				return PTR_ERR(base);
 			break;