Allow the PMT class to read discovery headers from either PCI MMIO or
ACPI-provided entries, depending on the discovery source. The new
source-aware fetch helper retrieves the first two QWORDs for both paths
while keeping the mapped discovery table available for users such as
crashlog.

Split intel_pmt_populate_entry() into source-specific resolvers:
  - pmt_resolve_access_pci(): handles both ACCESS_LOCAL and ACCESS_BARID
    for PCI-backed devices and sets entry->pcidev. Same existing
    functionality.
  - pmt_resolve_access_acpi(): handles only ACCESS_BARID for ACPI-backed
    devices, rejecting ACCESS_LOCAL which has no valid semantics without
    a physical discovery resource.

This maintains existing PCI behavior and makes no functional changes
for PCI devices.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
---

V2 changes:
- In pmt_resolve_access_acpi(), moved dev_err() call to single line
  instead of split across two lines
- Restructured error handling in intel_pmt_populate_entry(), moving error
  returns from after switch/case into each case statement for better
  readability
- Addressed Ilpo's feedback on error message formatting and error
  handling patterns

 drivers/platform/x86/intel/pmt/class.c | 123 +++++++++++++++++++++++--
 1 file changed, 114 insertions(+), 9 deletions(-)

diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/intel/pmt/class.c
index 3fcea6a6e763..64678f55a20e 100644
--- a/drivers/platform/x86/intel/pmt/class.c
+++ b/drivers/platform/x86/intel/pmt/class.c
@@ -205,9 +205,9 @@ struct class intel_pmt_class = {
 };
 EXPORT_SYMBOL_GPL(intel_pmt_class);
 
-static int intel_pmt_populate_entry(struct intel_pmt_entry *entry,
-				    struct intel_vsec_device *ivdev,
-				    int idx)
+static int pmt_resolve_access_pci(struct intel_pmt_entry *entry,
+				  struct intel_vsec_device *ivdev,
+				  int idx)
 {
 	struct pci_dev *pci_dev = to_pci_dev(ivdev->dev);
 	struct device *dev = &ivdev->auxdev.dev;
@@ -287,6 +287,81 @@ static int intel_pmt_populate_entry(struct intel_pmt_entry *entry,
 	}
 
 	entry->pcidev = pci_dev;
+
+	return 0;
+}
+
+static int pmt_resolve_access_acpi(struct intel_pmt_entry *entry,
+				   struct intel_vsec_device *ivdev)
+{
+	struct pci_dev *pci_dev = NULL;
+	struct device *dev = &ivdev->auxdev.dev;
+	struct intel_pmt_header *header = &entry->header;
+	u8 bir;
+
+	if (dev_is_pci(ivdev->dev))
+		pci_dev = to_pci_dev(ivdev->dev);
+
+	/*
+	 * The base offset should always be 8 byte aligned.
+	 *
+	 * For non-local access types the lower 3 bits of base offset
+	 * contains the index of the base address register where the
+	 * telemetry can be found.
+	 */
+	bir = GET_BIR(header->base_offset);
+
+	switch (header->access_type) {
+	case ACCESS_BARID:
+		/* ACPI platform drivers use base_addr */
+		if (ivdev->base_addr) {
+			entry->base_addr = ivdev->base_addr +
+					   GET_ADDRESS(header->base_offset);
+			break;
+		}
+
+		/* If base_addr is not provided, then this is an ACPI companion device */
+		if (!pci_dev) {
+			dev_err(dev, "ACCESS_BARID requires PCI BAR resources or base_addr\n");
+			return -EINVAL;
+		}
+
+		entry->base_addr = pci_resource_start(pci_dev, bir) +
+			GET_ADDRESS(header->base_offset);
+		break;
+	default:
+		dev_err(dev, "Unsupported access type %d for ACPI based PMT\n",
+			header->access_type);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int intel_pmt_populate_entry(struct intel_pmt_entry *entry,
+				    struct intel_vsec_device *ivdev,
+				    int idx)
+{
+	struct intel_pmt_header *header = &entry->header;
+	struct device *dev = &ivdev->auxdev.dev;
+	int ret;
+
+	switch (ivdev->src) {
+	case INTEL_VSEC_DISC_PCI:
+		ret = pmt_resolve_access_pci(entry, ivdev, idx);
+		if (ret)
+			return ret;
+		break;
+	case INTEL_VSEC_DISC_ACPI:
+		ret = pmt_resolve_access_acpi(entry, ivdev);
+		if (ret)
+			return ret;
+		break;
+	default:
+		dev_err(dev, "Unknown discovery source: %d\n", ivdev->src);
+		return -EINVAL;
+	}
+
 	entry->guid = header->guid;
 	entry->size = header->size;
 	entry->cb = ivdev->priv_data;
@@ -371,18 +446,48 @@ static int intel_pmt_dev_register(struct intel_pmt_entry *entry,
 	return ret;
 }
 
+static int pmt_get_headers(struct intel_vsec_device *ivdev, int idx,
+			   struct intel_pmt_entry *entry, u64 headers[2])
+{
+	struct device *dev = &ivdev->auxdev.dev;
+
+	switch (ivdev->src) {
+	case INTEL_VSEC_DISC_PCI: {
+		void __iomem *disc_table;
+
+		disc_table = devm_ioremap_resource(dev, &ivdev->resource[idx]);
+		if (IS_ERR(disc_table))
+			return PTR_ERR(disc_table);
+
+		memcpy_fromio(headers, disc_table, 2 * sizeof(u64));
+
+		/* Used by crashlog driver */
+		entry->disc_table = disc_table;
+
+		return 0;
+	}
+	case INTEL_VSEC_DISC_ACPI:
+		memcpy(headers, &ivdev->acpi_disc[idx][0], 2 * sizeof(u64));
+
+		return 0;
+	default:
+		dev_err(dev, "Unknown discovery source type: %d\n", ivdev->src);
+		break;
+	}
+
+	return -EINVAL;
+}
+
 static int pmt_read_header(struct intel_vsec_device *ivdev, int idx,
 			   struct intel_pmt_entry *entry)
 {
 	struct intel_pmt_header *header = &entry->header;
-	struct device *dev = &ivdev->auxdev.dev;
 	u64 headers[2];
+	int ret;
 
-	entry->disc_table = devm_ioremap_resource(dev, &ivdev->resource[idx]);
-	if (IS_ERR(entry->disc_table))
-		return PTR_ERR(entry->disc_table);
-
-	memcpy_fromio(headers, entry->disc_table, 2 * sizeof(u64));
+	ret = pmt_get_headers(ivdev, idx, entry, headers);
+	if (ret)
+		return ret;
 
 	header->access_type = FIELD_GET(PMT_ACCESS_TYPE, headers[0]);
 	header->telem_type = FIELD_GET(PMT_TELEM_TYPE, headers[0]);
-- 
2.43.0