Re: [PATCH 1/1] PM: runtime: change stub pm_runtime_get_if_active() return 1 when !CONFIG_PM

[Alex Elder <elder@ieee.org>]

On 10/29/26 11:30 AM, Frank.Li@oss.nxp.com wrote:
> From: Frank Li <Frank.Li@nxp.com>
> 
> When CONFIG_PM is not enabled, all devices runtime PM state should be
> treated as active.

Should be treated as if runtime PM were enabled for the device,
and the runtime status is active.

It's a subtle distinction but the previous behavior returned
EINVAL, which means "runtime PM is disabled for the device".

Anyway, for the IPA use of this function, this looks correct.

Acked-by: Alex Elder <elder@riscstar.com>

> 
> __pm_runtime_resume() returns 1 (called by pm_runtime_get()).
> pm_runtime_get_if_active() is the try-and-get version of pm_runtime_get().
> stub pm_runtime_active() also returns true. So pm_runtime_get_if_active()
> should return the same value as the stub pm_runtime_get(), which is 1.
> 
> Analysis of all callers and their behavior with old (-EINVAL) vs new (1):
> 
> Pattern A: if (!pm_runtime_get_if_active(dev)) -- no impact
>    Both -EINVAL and 1 are non-zero, so !ret is false in both cases.
>    Callers: drivers/accel/ethosu/ethosu_perfmon.c,
>             drivers/gpu/drm/msm/adreno/a6xx_gmu.c,
>             drivers/gpu/drm/msm/msm_perfcntr.c,
>             drivers/gpu/drm/v3d/v3d_mmu.c,
>             drivers/gpu/drm/v3d/v3d_perfmon.c (x4),
>             drivers/media/i2c/gc08a3.c gc05a2.c og0ve1b.c ov6211.c,
>             drivers/media/i2c/ccs/ccs-core.c s5kjn1.c lm3560.c (x2),
>             drivers/media/i2c/s5k3m5.c thp7312.c imx283.c ov64a40.c,
>             drivers/media/pci/intel/ipu6/ipu6-buttress.c,
>             sound/hda/core/device.c
> 
> Pattern B: if (!ret) after get -- no impact
>    Both -EINVAL and 1 are non-zero, !ret is false in both cases.
>    drivers/gpu/drm/amd/pm/amdgpu_pm.c (comment says "allow access"
>      in kernels without CONFIG_PM), drivers/pci/pci.c
> 
> Pattern C: ret > 0 / ret <= 0 / ret != 1 checks -- FIXED
>    drivers/usb/core/offload.c: checks (!= 1), old -EINVAL caused
>      -EBUSY even with !CONFIG_PM. Fixed: now returns 1, proceeds.
>    drivers/accel/ivpu/ivpu_job.c: drm_WARN_ON(<= 0), old -EINVAL
>      spuriously triggered WARN. Fixed: 1 > 0, no warn.
>    drivers/gpu/drm/i915/intel_runtime_pm.c: checks (<= 0), old
>      -EINVAL triggered error path. Fixed: 1 > 0, correct path.
>    drivers/accel/ivpu/ivpu_sysfs.c: (> 0), old skipped freq read.
>      Fixed: proceeds correctly without CONFIG_PM.
>    drivers/gpu/drm/xe/xe_pm.c: wraps (> 0), all xe callers
>      (xe_bo.c, xe_shrinker.c, xe_vsec.c, xe_ggtt.c, xe_guc_ct.c,
>      xe_pxp.c) now correctly treat !CONFIG_PM as active.
>    drivers/net/ipa/ipa_smp2p.c: power_on = (> 0), now correctly true.
>    drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c: (> 0), now correctly
>      executes stall register update.
>    drivers/staging/media/ipu7/ipu7-buttress.c: active (<= 0) early
>      return now skipped, correctly proceeds.
> 
> Pattern D: explicit -EINVAL check
>    drivers/hwmon/prom21-xhci.c: checks (> 0) then (== -EINVAL).
>      Old: took -EINVAL fallback. New: takes (> 0) fast path.
>      Both succeed when CONFIG_PM is disabled; functionally equivalent.
>    drivers/hwmon/eic7700-pvt.c: call is guarded by IS_ENABLED(CONFIG_PM),
>      stub is never reached. No impact.
> 
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Andrzej Kacprowski <andrzej.kacprowski@linux.intel.com>
> Cc: Karol Wachowski <karol.wachowski@linux.intel.com>
> Cc: Oded Gabbay <ogabbay@kernel.org>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Tvrtko Ursulin <tursulin@ursulin.net>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: "Thomas Hellstrom" <thomas.hellstrom@linux.intel.com>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Simona Vetter <simona@ffwll.ch>
> Cc: Alex Elder <elder@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: "Joerg Roedel" <joro@8bytes.org>
> Cc: Rob Clark <robin.clark@oss.qualcomm.com>
> Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Cc: Guan-Yu Lin <guanyulin@google.com>
> Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
> Cc: linux-pm@vger.kernel.org
> Cc: linux-usb@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: intel-xe@lists.freedesktop.org
> Cc: linux-hwmon@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: iommu@lists.linux.dev
> Cc: linux-arm-msm@vger.kernel.org
> Cc: linux-media@vger.kernel.org
> Cc: linux-staging@lists.linux.dev
> Cc: netdev@vger.kernel.org
> Cc: imx@lists.linux.dev
> Cc: Rob Herring (Arm) <robh@kernel.org>
> ---
>   include/linux/pm_runtime.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
> index 64921b10ac74f..de9e7518ecef2 100644
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -280,7 +280,7 @@ static inline int pm_runtime_get_if_in_use(struct device *dev)
>   }
>   static inline int pm_runtime_get_if_active(struct device *dev)
>   {
> -	return -EINVAL;
> +	return 1;
>   }
>   static inline int __pm_runtime_set_status(struct device *dev,
>   					    unsigned int status) { return 0; }