Re: [PATCH V2 08/17] platform/x86/intel/pmc: Add ACPI PWRM telemetry driver for Nova Lake S

Ilpo Järvinen
2026-04-07T12:57:02Z

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

> Add an ACPI-based PMC PWRM telemetry driver for Nova Lake S. The driver
> locates PMT discovery data in _DSD under the Intel VSEC UUID, parses it,
> and registers telemetry regions with the PMT/VSEC framework so PMC
> telemetry is exposed via existing PMT interfaces.
>
> Export pmc_parse_telem_dsd() and pmc_find_telem_guid() to support ACPI
> discovery in other PMC drivers (e.g., ssram_telemetry) without duplicating
> ACPI parsing logic. Also export acpi_disc_t typedef from core.h for callers
> to properly declare discovery table arrays.
>
> Selected by INTEL_PMC_CORE. Existing PCI functionality is preserved.
>
> Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> ---
>
> V2 changes:
> - Added explicit <linux/uuid.h> include for guid_t type availability in
> core.h
> - Added explicit <linux/bits.h> include in pwrm_telemetry.c for GENMASK()
> - Added <linux/cleanup.h> and converted goto based cleanup to __free()
> attributes per Ilpo's feedback
> - Combined u64 hdr0 and u64 hdr1 into single declaration
> - Converted pmc_parse_telem_dsd() to return acpi_disc directly with
> ERR_PTR() for failures
> - Added braces around _DSD evaluation failure path
>
> drivers/platform/x86/intel/pmc/Kconfig | 14 ++
> drivers/platform/x86/intel/pmc/Makefile | 2 +
> drivers/platform/x86/intel/pmc/core.h | 15 ++
> .../platform/x86/intel/pmc/pwrm_telemetry.c | 214 ++++++++++++++++++
> 4 files changed, 245 insertions(+)
> create mode 100644 drivers/platform/x86/intel/pmc/pwrm_telemetry.c
>
> diff --git a/drivers/platform/x86/intel/pmc/Kconfig b/drivers/platform/x86/intel/pmc/Kconfig
> index 0f19dc7edcf9..937186b0b5dd 100644
> --- a/drivers/platform/x86/intel/pmc/Kconfig
> +++ b/drivers/platform/x86/intel/pmc/Kconfig
> @@ -9,6 +9,7 @@ config INTEL_PMC_CORE
> depends on ACPI
> depends on INTEL_PMT_TELEMETRY
> select INTEL_PMC_SSRAM_TELEMETRY
> + select INTEL_PMC_PWRM_TELEMETRY
> help
> The Intel Platform Controller Hub for Intel Core SoCs provides access
> to Power Management Controller registers via various interfaces. This
> @@ -39,3 +40,16 @@ config INTEL_PMC_SSRAM_TELEMETRY
> (including sysfs).
>
> This option is selected by INTEL_PMC_CORE.
> +
> +config INTEL_PMC_PWRM_TELEMETRY
> + tristate
> + help
> + This driver discovers PMC PWRM telemetry regions described in ACPI
> + _DSD and registers them with the Intel VSEC framework as Intel PMT
> + telemetry devices.
> +
> + It validates the ACPI discovery data and publishes the discovered
> + regions so they can be accessed through the Intel PMT telemetry
> + interfaces (including sysfs).
> +
> + This option is selected by INTEL_PMC_CORE.
> diff --git a/drivers/platform/x86/intel/pmc/Makefile b/drivers/platform/x86/intel/pmc/Makefile
> index bb960c8721d7..fdbb768f7b09 100644
> --- a/drivers/platform/x86/intel/pmc/Makefile
> +++ b/drivers/platform/x86/intel/pmc/Makefile
> @@ -12,3 +12,5 @@ obj-$(CONFIG_INTEL_PMC_CORE) += intel_pmc_core_pltdrv.o
> # Intel PMC SSRAM driver
> intel_pmc_ssram_telemetry-y += ssram_telemetry.o
> obj-$(CONFIG_INTEL_PMC_SSRAM_TELEMETRY) += intel_pmc_ssram_telemetry.o
> +intel_pmc_pwrm_telemetry-y += pwrm_telemetry.o
> +obj-$(CONFIG_INTEL_PMC_PWRM_TELEMETRY) += intel_pmc_pwrm_telemetry.o
> diff --git a/drivers/platform/x86/intel/pmc/core.h b/drivers/platform/x86/intel/pmc/core.h
> index 118c8740ad3a..37ea1caf1817 100644
> --- a/drivers/platform/x86/intel/pmc/core.h
> +++ b/drivers/platform/x86/intel/pmc/core.h
> @@ -14,10 +14,14 @@
>
> #include <linux/acpi.h>
> #include <linux/bits.h>
> +#include <linux/cleanup.h>
> #include <linux/platform_device.h>
> +#include <linux/uuid.h>
>
> struct telem_endpoint;
>
> +DEFINE_FREE(pmc_acpi_free, void *, if (_T) ACPI_FREE(_T))
> +
> #define SLP_S0_RES_COUNTER_MASK GENMASK(31, 0)
>
> #define PMC_BASE_ADDR_DEFAULT 0xFE000000
> @@ -562,6 +566,8 @@ int pmc_core_pmt_get_blk_sub_req(struct pmc_dev *pmcdev, struct pmc *pmc,
> extern const struct file_operations pmc_core_substate_req_regs_fops;
> extern const struct file_operations pmc_core_substate_blk_req_fops;
>
> +extern const guid_t intel_vsec_guid;
> +
> #define pmc_for_each_mode(mode, pmc) \
> for (unsigned int __i = 0, __cond; \
> __cond = __i < (pmc)->num_lpm_modes, \
> @@ -583,4 +589,13 @@ static const struct file_operations __name ## _fops = { \
> .release = single_release, \
> }
>
> +struct intel_vsec_header;
> +union acpi_object;
> +
> +/* Avoid checkpatch warning */
> +typedef u32 (*acpi_disc_t)[4];
> +
> + acpi_disc_t pmc_parse_telem_dsd(union acpi_object *obj,

Remove extra space.

> + struct intel_vsec_header *header);

This doesn't seem to align to (.

> +union acpi_object *pmc_find_telem_guid(union acpi_object *dsd);
> #endif /* PMC_CORE_H */
> diff --git a/drivers/platform/x86/intel/pmc/pwrm_telemetry.c b/drivers/platform/x86/intel/pmc/pwrm_telemetry.c
> new file mode 100644
> index 000000000000..e852ee2d6d9f
> --- /dev/null
> +++ b/drivers/platform/x86/intel/pmc/pwrm_telemetry.c
> @@ -0,0 +1,214 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Intel PMC PWRM ACPI driver
> + *
> + * Copyright (C) 2025, Intel Corporation
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/bits.h>
> +#include <linux/bitfield.h>
> +#include <linux/cleanup.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/intel_vsec.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/resource.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +#include <linux/uuid.h>
> +
> +#include "core.h"
> +
> +#define ENTRY_LEN 5
> +
> +/* DWORD2 */
> +#define DVSEC_ID_MASK GENMASK(15, 0)
> +#define NUM_ENTRIES_MASK GENMASK(23, 16)
> +#define ENTRY_SIZE_MASK GENMASK(31, 24)
> +
> +/* DWORD3 */
> +#define TBIR_MASK GENMASK(2, 0)
> +#define DISC_TBL_OFF_MASK GENMASK(31, 3)
> +
> +const guid_t intel_vsec_guid =
> + GUID_INIT(0x294903fb, 0x634d, 0x4fc7, 0xaf, 0x1f, 0x0f, 0xb9,
> + 0x56, 0xb0, 0x4f, 0xc1);
> +
> +static bool is_valid_entry(union acpi_object *pkg)
> +{
> + int i;
> +
> + if (!pkg || pkg->type != ACPI_TYPE_PACKAGE || pkg->package.count != ENTRY_LEN)
> + return false;
> +
> + if (pkg->package.elements[0].type != ACPI_TYPE_STRING)
> + return false;
> +
> + for (i = 1; i < ENTRY_LEN; i++)
> + if (pkg->package.elements[i].type != ACPI_TYPE_INTEGER)
> + return false;
> +
> + return true;
> +}
> +
> +u32 (*pmc_parse_telem_dsd(union acpi_object *obj,
> + struct intel_vsec_header *header))[4]

Can't you use acpi_disc_t here as well?

> +{
> + acpi_disc_t disc __free(kfree) = NULL;

This should not be indendepent but at the site of allocation (__free() =
NULL; is trappy pattern so better avoid it).

> + union acpi_object *vsec_pkg;
> + union acpi_object *disc_pkg;
> + u64 hdr0, hdr1;
> + int num_regions;
> + int i;
> +
> + if (!header)
> + return ERR_PTR(-EINVAL);
> +
> + if (!obj || obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 2)
> + return ERR_PTR(-EINVAL);
> +
> + /* First Package is DVSEC info */
> + vsec_pkg = &obj->package.elements[0];
> + if (!is_valid_entry(vsec_pkg))
> + return ERR_PTR(-EINVAL);
> +
> + hdr0 = vsec_pkg->package.elements[3].integer.value;
> + hdr1 = vsec_pkg->package.elements[4].integer.value;
> +
> + header->id = FIELD_GET(DVSEC_ID_MASK, hdr0);
> + header->num_entries = FIELD_GET(NUM_ENTRIES_MASK, hdr0);
> + header->entry_size = FIELD_GET(ENTRY_SIZE_MASK, hdr0);
> + header->tbir = FIELD_GET(TBIR_MASK, hdr1);
> + header->offset = FIELD_GET(DISC_TBL_OFF_MASK, hdr1);
> +
> + /* Second Package contains the discovery tables */
> + disc_pkg = &obj->package.elements[1];
> + if (disc_pkg->type != ACPI_TYPE_PACKAGE || disc_pkg->package.count < 1)
> + return ERR_PTR(-EINVAL);
> +
> + num_regions = disc_pkg->package.count;
> + if (header->num_entries != num_regions)
> + return ERR_PTR(-EINVAL);
> +
> + disc = kmalloc_array(num_regions, sizeof(*disc), GFP_KERNEL);
> + if (!disc)
> + return ERR_PTR(-ENOMEM);
> +
> + for (i = 0; i < num_regions; i++) {
> + union acpi_object *pkg;
> + u64 value;
> + int j;
> +
> + pkg = &disc_pkg->package.elements[i];
> + if (!is_valid_entry(pkg))
> + return ERR_PTR(-EINVAL);
> +
> + /* Element 0 is a descriptive string; DWORD values start at index 1. */
> + for (j = 1; j < ENTRY_LEN; j++) {
> + value = pkg->package.elements[j].integer.value;
> + if (value > U32_MAX)
> + return ERR_PTR(-ERANGE);
> +
> + disc[i][j - 1] = value;
> + }
> + }
> +
> + return no_free_ptr(disc);
> +}
> +EXPORT_SYMBOL_NS_GPL(pmc_parse_telem_dsd, "INTEL_PMC_CORE");

--
i.