Re: [PATCH V2 04/17] platform/x86/intel/pmt: Move header decode into common helper

[Ilpo Järvinen]

On Tue, 24 Mar 2026, David E. Box wrote:

> Unify PMT discovery table parsing by moving header decode logic into the
> class driver. A new helper, pmt_read_header(), now fills in the standard
> header fields from the discovery table, replacing the per-namespace
> pmt_header_decode callbacks in telemetry and crashlog.
> 
> This centralizes the discovery table bit-field definitions in class.h,
> removes duplicate decode code from telemetry and crashlog, and prepares the
> PMT class for additional discovery sources.
> 
> Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx>
> ---
> 
> V2 changes:
> - Added PMT_GET_SIZE_BYTES(v), addressing Ilpo feedback on macro naming
>   and unit clarity
> - Also in PMT_GET_SIZE_BYTES(v) change ((v) << 2) to ((v) * sizeof(u32))
>   for clarity
> - Removed unused macros from crashlog.c per feedback from Ilpo
> 
>  drivers/platform/x86/intel/pmt/class.c     | 37 +++++++++++++++-------
>  drivers/platform/x86/intel/pmt/class.h     | 15 +++++++--
>  drivers/platform/x86/intel/pmt/crashlog.c  | 23 --------------
>  drivers/platform/x86/intel/pmt/telemetry.c | 26 ---------------
>  4 files changed, 39 insertions(+), 62 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel/pmt/class.c b/drivers/platform/x86/intel/pmt/class.c
> index 9b315334a69b..d652b21261f0 100644
> --- a/drivers/platform/x86/intel/pmt/class.c
> +++ b/drivers/platform/x86/intel/pmt/class.c
> @@ -8,6 +8,7 @@
>   * Author: "Alexander Duyck" <alexander.h.duyck@xxxxxxxxxxxxxxx>
>   */
>  
> +#include <linux/bitfield.h>
>  #include <linux/kernel.h>
>  #include <linux/log2.h>
>  #include <linux/intel_vsec.h>
> @@ -368,26 +369,40 @@ static int intel_pmt_dev_register(struct intel_pmt_entry *entry,
>  	return ret;
>  }
>  
> -int intel_pmt_dev_create(struct intel_pmt_entry *entry, struct intel_pmt_namespace *ns,
> -			 struct intel_vsec_device *intel_vsec_dev, int idx)
> +static int pmt_read_header(struct intel_vsec_device *ivdev, int idx,
> +			   struct intel_pmt_entry *entry)
>  {
> -	struct device *dev = &intel_vsec_dev->auxdev.dev;
> -	struct resource	*disc_res;
> -	int ret;
> +	struct intel_pmt_header *header = &entry->header;
> +	struct device *dev = &ivdev->auxdev.dev;
> +	u64 headers[2];
>  
> -	disc_res = &intel_vsec_dev->resource[idx];
> -
> -	entry->disc_table = devm_ioremap_resource(dev, disc_res);
> +	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));
> +
> +	header->access_type = FIELD_GET(PMT_ACCESS_TYPE, headers[0]);
> +	header->telem_type = FIELD_GET(PMT_TELEM_TYPE, headers[0]);
> +	header->size = PMT_GET_SIZE_BYTES(headers[0]);

Hi David,

There might be something I'm missing that is not apparent from the code 
alone, but when I look the old code in pmt_crashlog_header_decode(), it 
has this:

#define SIZE_OFFSET            0xC
...
	header->size = GET_SIZE(readl(disc_table + SIZE_OFFSET));

...I can't understand how this transformation is equivalent as it was 
previously read from 0xC which would belong into header[1], right?

I think it warrants an explanation in changelog if it's an intended 
change.

-- 
 i.

> +	header->guid = FIELD_GET(PMT_GUID32, headers[0]);
> +	header->base_offset = FIELD_GET(PMT_BASE_OFFSET, headers[1]);
> +
> +	return 0;
> +}
> +
> +int intel_pmt_dev_create(struct intel_pmt_entry *entry, struct intel_pmt_namespace *ns,
> +			 struct intel_vsec_device *intel_vsec_dev, int idx)
> +{
> +	int ret;
> +
>  	if (ns->pmt_pre_decode) {
>  		ret = ns->pmt_pre_decode(intel_vsec_dev, entry);
>  		if (ret)
>  			return ret;
>  	}
>  
> -	ret = ns->pmt_header_decode(entry, dev);
> +	ret = pmt_read_header(intel_vsec_dev, idx, entry);
>  	if (ret)
>  		return ret;
>  
> @@ -397,11 +412,11 @@ int intel_pmt_dev_create(struct intel_pmt_entry *entry, struct intel_pmt_namespa
>  			return ret;
>  	}
>  
> -	ret = intel_pmt_populate_entry(entry, intel_vsec_dev, disc_res);
> +	ret = intel_pmt_populate_entry(entry, intel_vsec_dev, &intel_vsec_dev->resource[idx]);
>  	if (ret)
>  		return ret;
>  
> -	return intel_pmt_dev_register(entry, ns, dev);
> +	return intel_pmt_dev_register(entry, ns, &intel_vsec_dev->auxdev.dev);
>  }
>  EXPORT_SYMBOL_NS_GPL(intel_pmt_dev_create, "INTEL_PMT");
>  
> diff --git a/drivers/platform/x86/intel/pmt/class.h b/drivers/platform/x86/intel/pmt/class.h
> index 8a0db0ef58c1..96ebb15f0053 100644
> --- a/drivers/platform/x86/intel/pmt/class.h
> +++ b/drivers/platform/x86/intel/pmt/class.h
> @@ -11,6 +11,19 @@
>  
>  #include "telemetry.h"
>  
> +/* PMT Discovery Table DWORD 1 */
> +#define PMT_ACCESS_TYPE		GENMASK_ULL(3, 0)
> +#define PMT_TELEM_TYPE		GENMASK_ULL(7, 4)
> +#define PMT_SIZE		GENMASK_ULL(27, 12)
> +#define PMT_GUID32		GENMASK_ULL(63, 32)
> +
> +/* PMT Discovery Table DWORD 2 */
> +#define PMT_BASE_OFFSET		GENMASK_ULL(31, 0)
> +#define PMT_TELE_ID		GENMASK_ULL(63, 32)
> +
> +/* Convert DWORD size to bytes */
> +#define PMT_GET_SIZE_BYTES(h)	((FIELD_GET(PMT_SIZE, h)) * sizeof(u32))
> +
>  /* PMT access types */
>  #define ACCESS_BARID		2
>  #define ACCESS_LOCAL		3
> @@ -61,8 +74,6 @@ struct intel_pmt_entry {
>  struct intel_pmt_namespace {
>  	const char *name;
>  	struct xarray *xa;
> -	int (*pmt_header_decode)(struct intel_pmt_entry *entry,
> -				 struct device *dev);
>  	int (*pmt_pre_decode)(struct intel_vsec_device *ivdev,
>  			      struct intel_pmt_entry *entry);
>  	int (*pmt_post_decode)(struct intel_vsec_device *ivdev,
> diff --git a/drivers/platform/x86/intel/pmt/crashlog.c b/drivers/platform/x86/intel/pmt/crashlog.c
> index f936daf99e4d..ef1826b15cf4 100644
> --- a/drivers/platform/x86/intel/pmt/crashlog.c
> +++ b/drivers/platform/x86/intel/pmt/crashlog.c
> @@ -26,14 +26,8 @@
>  
>  /* Crashlog Discovery Header */
>  #define CONTROL_OFFSET		0x0
> -#define GUID_OFFSET		0x4
> -#define BASE_OFFSET		0x8
> -#define SIZE_OFFSET		0xC
> -#define GET_ACCESS(v)		((v) & GENMASK(3, 0))
>  #define GET_TYPE(v)		(((v) & GENMASK(7, 4)) >> 4)
>  #define GET_VERSION(v)		(((v) & GENMASK(19, 16)) >> 16)
> -/* size is in bytes */
> -#define GET_SIZE(v)		((v) * sizeof(u32))
>  
>  /*
>   * Type 1 Version 0
> @@ -516,28 +510,11 @@ static int pmt_crashlog_pre_decode(struct intel_vsec_device *ivdev,
>  	return 0;
>  }
>  
> -static int pmt_crashlog_header_decode(struct intel_pmt_entry *entry,
> -				      struct device *dev)
> -{
> -	void __iomem *disc_table = entry->disc_table;
> -	struct intel_pmt_header *header = &entry->header;
> -
> -	header->access_type = GET_ACCESS(readl(disc_table));
> -	header->guid = readl(disc_table + GUID_OFFSET);
> -	header->base_offset = readl(disc_table + BASE_OFFSET);
> -
> -	/* Size is measured in DWORDS, but accessor returns bytes */
> -	header->size = GET_SIZE(readl(disc_table + SIZE_OFFSET));
> -
> -	return 0;
> -}
> -
>  static DEFINE_XARRAY_ALLOC(crashlog_array);
>  static struct intel_pmt_namespace pmt_crashlog_ns = {
>  	.name = "crashlog",
>  	.xa = &crashlog_array,
>  	.pmt_pre_decode = pmt_crashlog_pre_decode,
> -	.pmt_header_decode = pmt_crashlog_header_decode,
>  };
>  
>  /*
> diff --git a/drivers/platform/x86/intel/pmt/telemetry.c b/drivers/platform/x86/intel/pmt/telemetry.c
> index d22f633638be..80773e3c3efa 100644
> --- a/drivers/platform/x86/intel/pmt/telemetry.c
> +++ b/drivers/platform/x86/intel/pmt/telemetry.c
> @@ -27,14 +27,6 @@
>  
>  #include "class.h"
>  
> -#define TELEM_SIZE_OFFSET	0x0
> -#define TELEM_GUID_OFFSET	0x4
> -#define TELEM_BASE_OFFSET	0x8
> -#define TELEM_ACCESS(v)		((v) & GENMASK(3, 0))
> -#define TELEM_TYPE(v)		(((v) & GENMASK(7, 4)) >> 4)
> -/* size is in bytes */
> -#define TELEM_SIZE(v)		(((v) & GENMASK(27, 12)) >> 10)
> -
>  /* Used by client hardware to identify a fixed telemetry entry*/
>  #define TELEM_CLIENT_FIXED_BLOCK_GUID	0x10000000
>  
> @@ -69,23 +61,6 @@ static bool pmt_telem_region_overlaps(struct device *dev, u32 guid, u32 type)
>  	return false;
>  }
>  
> -static int pmt_telem_header_decode(struct intel_pmt_entry *entry,
> -				   struct device *dev)
> -{
> -	void __iomem *disc_table = entry->disc_table;
> -	struct intel_pmt_header *header = &entry->header;
> -
> -	header->access_type = TELEM_ACCESS(readl(disc_table));
> -	header->guid = readl(disc_table + TELEM_GUID_OFFSET);
> -	header->base_offset = readl(disc_table + TELEM_BASE_OFFSET);
> -
> -	/* Size is measured in DWORDS, but accessor returns bytes */
> -	header->size = TELEM_SIZE(readl(disc_table));
> -	header->telem_type = TELEM_TYPE(readl(entry->disc_table));
> -
> -	return 0;
> -}
> -
>  static int pmt_telem_post_decode(struct intel_vsec_device *ivdev,
>  				 struct intel_pmt_entry *entry)
>  {
> @@ -135,7 +110,6 @@ static DEFINE_XARRAY_ALLOC(telem_array);
>  static struct intel_pmt_namespace pmt_telem_ns = {
>  	.name = "telem",
>  	.xa = &telem_array,
> -	.pmt_header_decode = pmt_telem_header_decode,
>  	.pmt_post_decode = pmt_telem_post_decode,
>  	.pmt_add_endpoint = pmt_telem_add_endpoint,
>  };
>