Re: [PATCH 6/7] drm/xe/vsec: Crescent Island PMT callbacks

On Thu, Aug 06, 2026 at 06:58:26AM -0700, Michael J. Ruhl wrote:
> CRI PMT support requires callbacks to access the discovery status
> and control areas.  Access is a common MMIO area that requires an
> index to be set before access is allowed.
> 
> Introduce the necessary callbacks to get the status and control
> information for CRI PMT usage.
> 
> Add the glue logic to register the CRI PMT functionality.
> 
> Signed-off-by: Michael J. Ruhl <[email protected]>
> ---
>  drivers/gpu/drm/xe/xe_vsec.c | 85 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 82 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_vsec.c b/drivers/gpu/drm/xe/xe_vsec.c
> index 3849f99c1c91..b84ec9088de7 100644
> --- a/drivers/gpu/drm/xe/xe_vsec.c
> +++ b/drivers/gpu/drm/xe/xe_vsec.c
> @@ -320,17 +320,90 @@ int xe_pmt_telem_read(struct device *dev, u32 guid, u64 *data, loff_t user_offse
>  	return count;
>  }
>  
> -static struct pmt_callbacks xe_pmt_cb = {
> +/**
> + * xe_pmt_read_reg() - read a crashlog register
> + * @dev: the xe device that registered the callback
> + * @guid: PMT guid of the crashlog instance
> + * @reg: data read from the PMT data structure
> + * @offset: which data to read from the PMT data structure
> + *
> + * Read the requested PMT register based on the pcie device and guid.  The
> + * supported struct is the Crashlog Type1 Version2.
> + *
> + * Currently this is for CRI only.
> + */
> +static int xe_pmt_read_reg(struct device *dev, u32 guid, u32 *reg, u32 offset)
> +{
> +	struct xe_device *xe = kdev_to_xe_device(dev);
> +	void __iomem *disc_addr = xe->mmio.regs;
> +	u32 inst;
> +
> +	if (FIELD_GET(GUID_DEVICE_ID, guid) != CRI_DEVICE_ID ||
> +	    FIELD_GET(GUID_CAP_TYPE, guid) != CRASHLOG)
> +		return -EINVAL;
> +
> +	inst = FIELD_GET(GUID_RECORD_ID, guid) == PUNIT ?
> +		CRI_CRASHLOG_PUNIT_DISC_OFFSET : CRI_CRASHLOG_OOBMSM_DISC_OFFSET;
> +	disc_addr += CRI_DISCOVERY_OFFSET + inst + offset;
> +
> +	guard(mutex)(&xe->pmt.lock);
> +
> +	xe_pm_runtime_get(xe);

We have guard(xe_pm_runtime)(xe), and this should also be the
outermost construct (i.e., do not use xe_pm_runtime_get(), as it can
wake the device, while other locks are held).

So this should either be:

guard(xe_pm_runtime)(xe);
guard(mutex)(&xe->pmt.lock);

Or, like the other in-tree usage with xe->pmt.lock in
xe_pmt_telem_read(), which calls xe_pm_runtime_get_if_active() while
holding the lock. This is fine because xe_pm_runtime_get_if_active()
cannot wake the device. This is most likely the correct choice, given
that this is a vfunc called by a different driver, and we have no way of
knowing whether that driver is holding locks that could create
problematic lock dependency chains if we wake the Xe device here.

Matt

> +
> +	xe->soc_remapper.set_telem_region(xe, CRI_IDX_TELEM_DISCOVERY);
> +
> +	memcpy_fromio(reg, disc_addr, sizeof(*reg));
> +
> +	xe_pm_runtime_put(xe);
> +
> +	return 0;
> +}
> +
> +static int xe_pmt_write_reg(struct device *dev, u32 guid, u32 reg, u32 offset)
> +{
> +	struct xe_device *xe = kdev_to_xe_device(dev);
> +	void __iomem *disc_addr = xe->mmio.regs;
> +	u32 inst;
> +
> +	if (FIELD_GET(GUID_DEVICE_ID, guid) != CRI_DEVICE_ID ||
> +	    FIELD_GET(GUID_CAP_TYPE, guid) != CRASHLOG)
> +		return -EINVAL;
> +
> +	inst = FIELD_GET(GUID_RECORD_ID, guid) == PUNIT ?
> +		CRI_CRASHLOG_PUNIT_DISC_OFFSET : CRI_CRASHLOG_OOBMSM_DISC_OFFSET;
> +	disc_addr += CRI_DISCOVERY_OFFSET + inst + offset;
> +
> +	guard(mutex)(&xe->pmt.lock);
> +
> +	xe_pm_runtime_get(xe);
> +
> +	xe->soc_remapper.set_telem_region(xe, CRI_IDX_TELEM_DISCOVERY);
> +
> +	memcpy_toio(disc_addr, &reg, sizeof(reg));
> +
> +	xe_pm_runtime_put(xe);
> +
> +	return 0;
> +}
> +
> +static struct pmt_callbacks xe_bmg_pmt_cb = {
> +	.read_telem = xe_pmt_telem_read,
> +};
> +
> +static struct pmt_callbacks xe_cri_pmt_cb = {
>  	.read_telem = xe_pmt_telem_read,
> +	.read_reg = xe_pmt_read_reg,
> +	.write_reg = xe_pmt_write_reg,
>  };
>  
>  static const int vsec_platforms[] = {
>  	[XE_BATTLEMAGE] = XE_VSEC_BMG,
> +	[XE_CRESCENTISLAND] = XE_VSEC_CRI,
>  };
>  
>  static enum xe_vsec get_platform_info(struct xe_device *xe)
>  {
> -	if (xe->info.platform > XE_BATTLEMAGE)
> +	if (xe->info.platform > XE_CRESCENTISLAND)
>  		return XE_VSEC_UNKNOWN;
>  
>  	return vsec_platforms[xe->info.platform];
> @@ -357,8 +430,14 @@ void xe_vsec_init(struct xe_device *xe)
>  
>  	switch (platform) {
>  	case XE_VSEC_BMG:
> -		info->priv_data = &xe_pmt_cb;
> +		info->priv_data = &xe_bmg_pmt_cb;
>  		break;
> +
> +	case XE_VSEC_CRI:
> +		info->priv_data = &xe_cri_pmt_cb;
> +		xe->soc_remapper.set_telem_region(xe, CRI_IDX_TELEM_DISCOVERY);
> +		break;
> +
>  	default:
>  		break;
>  	}
> -- 
> 2.43.0
>