On ti, 2015-12-15 at 20:10 +0200, Imre Deak wrote:
> In some cases we want to check whether we hold an RPM wakelock
> reference
> for the whole duration of a sequence. To achieve this add a new RPM
> atomic sequence
> counter that we increment any time the wakelock refcount drops to
> zero.
> Check whether the sequence number stays the same during the atomic
> section and that we hold the wakelock at the beginning of the
> section.
>
> Motivated by Chris.
>
> v2-v3:
> - unchanged
> v4:
> - swap the order of atomic_read() and assert_rpm_wakelock_held() in
> assert_rpm_atomic_begin() to avoid race
>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> (v3)
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 1 +
> drivers/gpu/drm/i915/intel_drv.h | 17 +++++++++++++++++
> drivers/gpu/drm/i915/intel_pm.c | 1 +
> drivers/gpu/drm/i915/intel_runtime_pm.c | 3 ++-
> 4 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h
> b/drivers/gpu/drm/i915/i915_drv.h
> index 2894716..00ce627 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1603,6 +1603,7 @@ struct skl_wm_level {
> */
> struct i915_runtime_pm {
> atomic_t wakeref_count;
> + atomic_t atomic_seq;
> bool suspended;
> bool irqs_enabled;
> };
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
> index d8e4aca..88d37eb 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1446,6 +1446,23 @@ assert_rpm_wakelock_held(struct
> drm_i915_private *dev_priv)
> "RPM wakelock ref not held during HW access");
> }
>
> +static inline int
> +assert_rpm_atomic_begin(struct drm_i915_private *dev_priv)
> +{
> + int seq = atomic_read(&dev_priv->pm.atomic_seq);
> +
> + assert_rpm_wakelock_held(dev_priv);
> +
> + return seq;
> +}
> +
> +static inline void
> +assert_rpm_atomic_end(struct drm_i915_private *dev_priv, int
> begin_seq)
> +{
> + WARN_ONCE(atomic_read(&dev_priv->pm.atomic_seq) !=
> begin_seq,
> + "HW access outside of RPM atomic section\n");
> +}
> +
> /**
> * disable_rpm_wakeref_asserts - disable the RPM assert checks
> * @dev_priv: i915 device instance
> diff --git a/drivers/gpu/drm/i915/intel_pm.c
> b/drivers/gpu/drm/i915/intel_pm.c
> index 6c08537..6eb9606 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -7248,4 +7248,5 @@ void intel_pm_setup(struct drm_device *dev)
>
> dev_priv->pm.suspended = false;
> atomic_set(&dev_priv->pm.wakeref_count, 0);
> + atomic_set(&dev_priv->pm.atomic_seq, 0);
> }
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c
> b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 82c55a9..cee54ea 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -2283,7 +2283,8 @@ void intel_runtime_pm_put(struct
> drm_i915_private *dev_priv)
> struct device *device = &dev->pdev->dev;
>
> assert_rpm_wakelock_held(dev_priv);
> - atomic_dec(&dev_priv->pm.wakeref_count);
> + if (atomic_dec_and_test(&dev_priv->pm.wakeref_count))
> + atomic_inc(&dev_priv->pm.atomic_seq);
>
> pm_runtime_mark_last_busy(device);
> pm_runtime_put_autosuspend(device);
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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