Re: [PATCH 1/5] pmt: Add register access callbacks

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 27 Jan 2026, "Michael J. Ruhl" <michael.j.ruhl@intel.com> wrote:
> Some HW does not have the explicit access via MMIO.  Allow
> for parent drivers to control access to the status/control
> path.

I think this is quite vague, and could use some copy-paste from the
cover letter, for posterity.

BR,
Jani.

>
> Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
> ---
>  drivers/platform/x86/intel/pmt/crashlog.c | 39 +++++++++++++++++++++--
>  include/linux/intel_vsec.h                | 26 +++++++++++----
>  2 files changed, 55 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/platform/x86/intel/pmt/crashlog.c b/drivers/platform/x86/intel/pmt/crashlog.c
> index b0393c9c5b4b..978b35d56888 100644
> --- a/drivers/platform/x86/intel/pmt/crashlog.c
> +++ b/drivers/platform/x86/intel/pmt/crashlog.c
> @@ -129,7 +129,19 @@ static void pmt_crashlog_rmw(struct crashlog_entry *crashlog, u32 bit, bool set)
>  {
>  	const struct crashlog_control *control = &crashlog->info->control;
>  	struct intel_pmt_entry *entry = &crashlog->entry;
> -	u32 reg = readl(entry->disc_table + control->offset);
> +	u32 guid = entry->header.guid;
> +	u32 reg;
> +	int err;
> +
> +	if (entry->cb->read_reg) {
> +		err = entry->cb->read_reg(entry->pcidev, guid, &reg, control->offset);
> +		if (err) {
> +			pr_err("%s: failed to read reg: %d\n", __func__, err);
> +			return;
> +		}
> +	} else {
> +		reg = readl(entry->disc_table + control->offset);
> +	}
>  
>  	reg &= ~control->trigger_mask;
>  
> @@ -138,14 +150,35 @@ static void pmt_crashlog_rmw(struct crashlog_entry *crashlog, u32 bit, bool set)
>  	else
>  		reg &= ~bit;
>  
> -	writel(reg, entry->disc_table + control->offset);
> +	if (entry->cb->write_reg) {
> +		err = entry->cb->write_reg(entry->pcidev, guid, reg, control->offset);
> +		if (err) {
> +			pr_err("%s: failed to write reg: %d\n", __func__, err);
> +			return;
> +		}
> +	} else {
> +		writel(reg, entry->disc_table + control->offset);
> +	}
>  }
>  
>  /* Read the status register and see if the specified @bit is set */
>  static bool pmt_crashlog_rc(struct crashlog_entry *crashlog, u32 bit)
>  {
>  	const struct crashlog_status *status = &crashlog->info->status;
> -	u32 reg = readl(crashlog->entry.disc_table + status->offset);
> +	struct intel_pmt_entry *entry = &crashlog->entry;
> +	u32 guid = entry->header.guid;
> +	u32 reg;
> +	int err;
> +
> +	if (entry->cb->read_reg) {
> +		err = entry->cb->read_reg(entry->pcidev, guid, &reg, status->offset);
> +		if (err) {
> +			pr_err("%s: failed to read reg: %d\n", __func__, err);
> +			return false;
> +		}
> +	} else {
> +		reg = readl(crashlog->entry.disc_table + status->offset);
> +	}
>  
>  	return !!(reg & bit);
>  }
> diff --git a/include/linux/intel_vsec.h b/include/linux/intel_vsec.h
> index 1a0f357c2427..5416f84aca40 100644
> --- a/include/linux/intel_vsec.h
> +++ b/include/linux/intel_vsec.h
> @@ -80,16 +80,28 @@ enum intel_vsec_quirks {
>  
>  /**
>   * struct pmt_callbacks - Callback infrastructure for PMT devices
> - * @read_telem: when specified, called by client driver to access PMT
> - * data (instead of direct copy).
> - * * pdev:  PCI device reference for the callback's use
> - * * guid:  ID of data to acccss
> - * * data:  buffer for the data to be copied
> - * * off:   offset into the requested buffer
> - * * count: size of buffer
> + * ->read_telem() when specified, called by client driver to access PMT data (instead
> + * of direct copy).
> + * @pdev:  PCI device reference for the callback's use
> + * @guid:  ID of data to access
> + * @data:  buffer for the data to be copied
> + * @off:   offset into the requested buffer
> + * @count: size of buffer
> + * ->read_reg() when specified called by client driver to read PMT state
> + * @pdev: PCI device reference for the callback's use
> + * @guid: ID of data to access
> + * @data: buffer for the register data to be read
> + * @offset: offset of control register to access
> + * ->write_reg() when specified called by client driver to write PMT state
> + * @pdev: PCI device reference for the callback's use
> + * @guid: ID of data to access
> + * @data: buffer data to be written to the register
> + * @offset: offset of control register to access
>   */
>  struct pmt_callbacks {
>  	int (*read_telem)(struct pci_dev *pdev, u32 guid, u64 *data, loff_t off, u32 count);
> +	int (*read_reg)(struct pci_dev *pdev, u32 guid, u32 *data, u32 offset);
> +	int (*write_reg)(struct pci_dev *pdev, u32 guid, u32 data, u32 offset);
>  };
>  
>  struct vsec_feature_dependency {

-- 
Jani Nikula, Intel