Re: [PATCH 12/22] platform/x86/intel/pmt: Unify header fetch and add ACPI source

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Thu, 12 Mar 2026, David E. Box wrote:

> 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>
> ---
>  drivers/platform/x86/intel/pmt/class.c | 124 +++++++++++++++++++++++--
>  1 file changed, 115 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/intel/pmt/class.c
> index f94f51178043..ddd9c4bf7323 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 +287,82 @@ 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");

IMO the extra line is not very useful here.

> +			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);
> +		break;
> +	case INTEL_VSEC_DISC_ACPI:
> +		ret = pmt_resolve_access_acpi(entry, ivdev);
> +		break;
> +	default:
> +		dev_err(dev, "Unknown discovery source: %d\n", ivdev->src);
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	if (ret)
> +		return ret;

Instead of deferring to after the switch/case, I'd prefer you handle the 
errors within the cases as it, while longer by a few lines, makes 
following the logic easier.

> +
>  	entry->guid = header->guid;
>  	entry->size = header->size;
>  	entry->cb = ivdev->priv_data;
> @@ -371,18 +447,48 @@ 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]);
> 

-- 
 i.