Re: [PATCH v6] drm/xe/pm: Disable RPM for SR-IOV VFs

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Tue, Aug 12, 2025 at 10:06:13PM +0530, Satyanarayana K V P wrote:
> VFs without native PCIe Power Management (PM) capabilities inherit their
> PF's power state as per PCIe specifications(§5.10.1 PCIe Base Spec 7.0).
> Enabling Runtime Power Management (RPM) for these VFs trigger unnecessary
> driver suspend/resume operations that ultimately perform no PCI-level power
> transition.
> 
> Since VFs without PM capabilities cannot independently enter low-power
> states, the existing RPM workflow becomes redundant:
> 1. Driver executes full suspend/resume sequence
> 2. PCI PM transition step becomes no-op
> 3. VF power state remains tied to PF's status
> 
> Disabling RPM for VFs eliminates this redundant processing while
> maintaining proper power management through PF dependency. This
> optimization ensures VFs follow their PF's power state without superfluous
> runtime handling.
> 
> Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Michał Winiarski <michal.winiarski@intel.com>
> Cc: Anshuman Gupta <anshuman.gupta@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Maarten Lankhorst <dev@lankhorst.se>

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

and pushing

> 
> ---
> V5 -> V6:
> - Updated comment (Rodrigo).
> 
> V4 -> V5:
> - Disable RPM for VFs without checking pm_cap (Rodrigo).
> - Updated commit title.
> 
> V3 -> V4:
> - Fixed review comments (Rodrigo & Maarten)
> 
> V2 -> V3:
> - Fixed review comments (Michal Wajdeczko).
> 
> V1 -> V2:
> - Disable RPM only for VF devices when PM cap is not implemented.
> ---
>  drivers/gpu/drm/xe/xe_pm.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
> index 5e8126ca8e27..51934d5dc44f 100644
> --- a/drivers/gpu/drm/xe/xe_pm.c
> +++ b/drivers/gpu/drm/xe/xe_pm.c
> @@ -247,6 +247,10 @@ static void xe_pm_runtime_init(struct xe_device *xe)
>  {
>  	struct device *dev = xe->drm.dev;
>  
> +	/* Our current VFs do not support RPM. so, disable it */
> +	if (IS_SRIOV_VF(xe))
> +		return;
> +
>  	/*
>  	 * Disable the system suspend direct complete optimization.
>  	 * We need to ensure that the regular device suspend/resume functions
> @@ -367,6 +371,10 @@ static void xe_pm_runtime_fini(struct xe_device *xe)
>  {
>  	struct device *dev = xe->drm.dev;
>  
> +	/* Our current VFs do not support RPM. so, disable it */
> +	if (IS_SRIOV_VF(xe))
> +		return;
> +
>  	pm_runtime_get_sync(dev);
>  	pm_runtime_forbid(dev);
>  }
> -- 
> 2.43.0
>