diff mbox

[v2] drm/i915/pmu: Fix sleep under atomic in RC6 readout

Message ID 20180206183311.17924-1-tvrtko.ursulin@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Tvrtko Ursulin Feb. 6, 2018, 6:33 p.m. UTC
From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

We are not allowed to call intel_runtime_pm_get from the PMU counter read
callback since the former can sleep, and the latter is running under IRQ
context.

To workaround this, we record the last known RC6 and while runtime
suspended estimate its increase by querying the runtime PM core
timestamps.

Downside of this approach is that we can temporarily lose a chunk of RC6
time, from the last PMU read-out to runtime suspend entry, but that will
eventually catch up, once device comes back online and in the presence of
PMU queries.

Also, we have to be careful not to overshoot the RC6 estimate, so once
resumed after a period of approximation, we only update the counter once
it catches up. With the observation that RC6 is increasing while the
device is suspended, this should not pose a problem and can only cause
slight inaccuracies due clock base differences.

v2: Simplify by estimating on top of PM core counters. (Imre)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104943
Fixes: 6060b6aec03c ("drm/i915/pmu: Add RC6 residency metrics")
Testcase: igt/perf_pmu/rc6-runtime-pm
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/i915/i915_pmu.c | 93 ++++++++++++++++++++++++++++++++++-------
 drivers/gpu/drm/i915/i915_pmu.h |  6 +++
 2 files changed, 84 insertions(+), 15 deletions(-)

Comments

Tvrtko Ursulin Feb. 7, 2018, 9:20 a.m. UTC | #1
On 06/02/2018 21:54, Imre Deak wrote:
> Hi Rafael,
> 
> On Tue, Feb 06, 2018 at 09:11:02PM +0000, Chris Wilson wrote:
>> Quoting Tvrtko Ursulin (2018-02-06 18:33:11)
>>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>
>>> We are not allowed to call intel_runtime_pm_get from the PMU counter read
>>> callback since the former can sleep, and the latter is running under IRQ
>>> context.
>>>
>>> To workaround this, we record the last known RC6 and while runtime
>>> suspended estimate its increase by querying the runtime PM core
>>> timestamps.
>>>
>>> Downside of this approach is that we can temporarily lose a chunk of RC6
>>> time, from the last PMU read-out to runtime suspend entry, but that will
>>> eventually catch up, once device comes back online and in the presence of
>>> PMU queries.
>>>
>>> Also, we have to be careful not to overshoot the RC6 estimate, so once
>>> resumed after a period of approximation, we only update the counter once
>>> it catches up. With the observation that RC6 is increasing while the
>>> device is suspended, this should not pose a problem and can only cause
>>> slight inaccuracies due clock base differences.
>>>
>>> v2: Simplify by estimating on top of PM core counters. (Imre)
>>>
>>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104943
>>> Fixes: 6060b6aec03c ("drm/i915/pmu: Add RC6 residency metrics")
>>> Testcase: igt/perf_pmu/rc6-runtime-pm
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Imre Deak <imre.deak@intel.com>
>>> Cc: Jani Nikula <jani.nikula@linux.intel.com>
>>> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
>>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>>> Cc: David Airlie <airlied@linux.ie>
>>> Cc: intel-gfx@lists.freedesktop.org
>>> Cc: dri-devel@lists.freedesktop.org
>>> ---
>>>   drivers/gpu/drm/i915/i915_pmu.c | 93 ++++++++++++++++++++++++++++++++++-------
>>>   drivers/gpu/drm/i915/i915_pmu.h |  6 +++
>>>   2 files changed, 84 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
>>> index 1c440460255d..bfc402d47609 100644
>>> --- a/drivers/gpu/drm/i915/i915_pmu.c
>>> +++ b/drivers/gpu/drm/i915/i915_pmu.c
>>> @@ -415,7 +415,81 @@ static int i915_pmu_event_init(struct perf_event *event)
>>>          return 0;
>>>   }
>>>   
>>> -static u64 __i915_pmu_event_read(struct perf_event *event)
>>> +static u64 get_rc6(struct drm_i915_private *i915, bool locked)
>>> +{
>>> +       unsigned long flags;
>>> +       u64 val;
>>> +
>>> +       if (intel_runtime_pm_get_if_in_use(i915)) {
>>> +               val = intel_rc6_residency_ns(i915, IS_VALLEYVIEW(i915) ?
>>> +                                                  VLV_GT_RENDER_RC6 :
>>> +                                                  GEN6_GT_GFX_RC6);
>>> +
>>> +               if (HAS_RC6p(i915))
>>> +                       val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6p);
>>> +
>>> +               if (HAS_RC6pp(i915))
>>> +                       val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6pp);
>>> +
>>> +               intel_runtime_pm_put(i915);
>>> +
>>> +               /*
>>> +                * If we are coming back from being runtime suspended we must
>>> +                * be careful not to report a larger value than returned
>>> +                * previously.
>>> +                */
>>> +
>>> +               if (!locked)
>>> +                       spin_lock_irqsave(&i915->pmu.lock, flags);
>>> +
>>> +               if (val >= i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur) {
>>> +                       i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = 0;
>>> +                       i915->pmu.sample[__I915_SAMPLE_RC6].cur = val;
>>> +               } else {
>>> +                       val = i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur;
>>> +               }
>>> +
>>> +               if (!locked)
>>> +                       spin_unlock_irqrestore(&i915->pmu.lock, flags);
>>> +       } else {
>>> +               struct pci_dev *pdev = i915->drm.pdev;
>>> +               struct device *kdev = &pdev->dev;
>>> +               unsigned long flags2;
>>> +
>>> +               /*
>>> +                * We are runtime suspended.
>>> +                *
>>> +                * Report the delta from when the device was suspended to now,
>>> +                * on top of the last known real value, as the approximated RC6
>>> +                * counter value.
>>> +                */
>>> +               if (!locked)
>>> +                       spin_lock_irqsave(&i915->pmu.lock, flags);
>>> +
>>> +               spin_lock_irqsave(&kdev->power.lock, flags2);
>>> +
>>> +               if (!i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur)
>>> +                       i915->pmu.suspended_jiffies_last =
>>> +                                               kdev->power.suspended_jiffies;
>>> +
>>> +               val = kdev->power.suspended_jiffies -
>>> +                     i915->pmu.suspended_jiffies_last;
>>> +               val += jiffies - kdev->power.accounting_timestamp;
>>> +
>>> +               spin_unlock_irqrestore(&kdev->power.lock, flags2);
>>> +
>>> +               val = jiffies_to_nsecs(val);
>>> +               val += i915->pmu.sample[__I915_SAMPLE_RC6].cur;
>>> +               i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val;
>>> +
>>> +               if (!locked)
>>> +                       spin_unlock_irqrestore(&i915->pmu.lock, flags);
>>> +       }
>>> +
>>> +       return val;
>>> +}
>>
>> I feel slightly dirty, but the dance checks out.
> 
> Would it be possible to add an RPM helper that provides the device's
> runtime suspend residency for the above purpose? This would be
> essentially what rtpm_suspended_time_show() provides.

That would indeed be much better since fishing into internals like the 
above is not very nice.

However, it would also be good not to delay this fix for too long by 
additional logistics, and keep it self-contained - easy to backport.

Regards,

Tvrtko
Chris Wilson Feb. 7, 2018, 9:36 a.m. UTC | #2
Quoting Tvrtko Ursulin (2018-02-07 09:20:27)
> 
> On 06/02/2018 21:54, Imre Deak wrote:
> > Hi Rafael,
> > 
> > On Tue, Feb 06, 2018 at 09:11:02PM +0000, Chris Wilson wrote:
> >> Quoting Tvrtko Ursulin (2018-02-06 18:33:11)
> >>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> >>>
> >>> We are not allowed to call intel_runtime_pm_get from the PMU counter read
> >>> callback since the former can sleep, and the latter is running under IRQ
> >>> context.
> >>>
> >>> To workaround this, we record the last known RC6 and while runtime
> >>> suspended estimate its increase by querying the runtime PM core
> >>> timestamps.
> >>>
> >>> Downside of this approach is that we can temporarily lose a chunk of RC6
> >>> time, from the last PMU read-out to runtime suspend entry, but that will
> >>> eventually catch up, once device comes back online and in the presence of
> >>> PMU queries.
> >>>
> >>> Also, we have to be careful not to overshoot the RC6 estimate, so once
> >>> resumed after a period of approximation, we only update the counter once
> >>> it catches up. With the observation that RC6 is increasing while the
> >>> device is suspended, this should not pose a problem and can only cause
> >>> slight inaccuracies due clock base differences.
> >>>
> >>> v2: Simplify by estimating on top of PM core counters. (Imre)
> >>>
> >>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> >>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104943
> >>> Fixes: 6060b6aec03c ("drm/i915/pmu: Add RC6 residency metrics")
> >>> Testcase: igt/perf_pmu/rc6-runtime-pm
> >>> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> >>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> >>> Cc: Imre Deak <imre.deak@intel.com>
> >>> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> >>> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> >>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> >>> Cc: David Airlie <airlied@linux.ie>
> >>> Cc: intel-gfx@lists.freedesktop.org
> >>> Cc: dri-devel@lists.freedesktop.org
> >>> ---
> >>>   drivers/gpu/drm/i915/i915_pmu.c | 93 ++++++++++++++++++++++++++++++++++-------
> >>>   drivers/gpu/drm/i915/i915_pmu.h |  6 +++
> >>>   2 files changed, 84 insertions(+), 15 deletions(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> >>> index 1c440460255d..bfc402d47609 100644
> >>> --- a/drivers/gpu/drm/i915/i915_pmu.c
> >>> +++ b/drivers/gpu/drm/i915/i915_pmu.c
> >>> @@ -415,7 +415,81 @@ static int i915_pmu_event_init(struct perf_event *event)
> >>>          return 0;
> >>>   }
> >>>   
> >>> -static u64 __i915_pmu_event_read(struct perf_event *event)
> >>> +static u64 get_rc6(struct drm_i915_private *i915, bool locked)
> >>> +{
> >>> +       unsigned long flags;
> >>> +       u64 val;
> >>> +
> >>> +       if (intel_runtime_pm_get_if_in_use(i915)) {
> >>> +               val = intel_rc6_residency_ns(i915, IS_VALLEYVIEW(i915) ?
> >>> +                                                  VLV_GT_RENDER_RC6 :
> >>> +                                                  GEN6_GT_GFX_RC6);
> >>> +
> >>> +               if (HAS_RC6p(i915))
> >>> +                       val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6p);
> >>> +
> >>> +               if (HAS_RC6pp(i915))
> >>> +                       val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6pp);
> >>> +
> >>> +               intel_runtime_pm_put(i915);
> >>> +
> >>> +               /*
> >>> +                * If we are coming back from being runtime suspended we must
> >>> +                * be careful not to report a larger value than returned
> >>> +                * previously.
> >>> +                */
> >>> +
> >>> +               if (!locked)
> >>> +                       spin_lock_irqsave(&i915->pmu.lock, flags);
> >>> +
> >>> +               if (val >= i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur) {
> >>> +                       i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = 0;
> >>> +                       i915->pmu.sample[__I915_SAMPLE_RC6].cur = val;
> >>> +               } else {
> >>> +                       val = i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur;
> >>> +               }
> >>> +
> >>> +               if (!locked)
> >>> +                       spin_unlock_irqrestore(&i915->pmu.lock, flags);
> >>> +       } else {
> >>> +               struct pci_dev *pdev = i915->drm.pdev;
> >>> +               struct device *kdev = &pdev->dev;
> >>> +               unsigned long flags2;
> >>> +
> >>> +               /*
> >>> +                * We are runtime suspended.
> >>> +                *
> >>> +                * Report the delta from when the device was suspended to now,
> >>> +                * on top of the last known real value, as the approximated RC6
> >>> +                * counter value.
> >>> +                */
> >>> +               if (!locked)
> >>> +                       spin_lock_irqsave(&i915->pmu.lock, flags);
> >>> +
> >>> +               spin_lock_irqsave(&kdev->power.lock, flags2);
> >>> +
> >>> +               if (!i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur)
> >>> +                       i915->pmu.suspended_jiffies_last =
> >>> +                                               kdev->power.suspended_jiffies;
> >>> +
> >>> +               val = kdev->power.suspended_jiffies -
> >>> +                     i915->pmu.suspended_jiffies_last;
> >>> +               val += jiffies - kdev->power.accounting_timestamp;
> >>> +
> >>> +               spin_unlock_irqrestore(&kdev->power.lock, flags2);
> >>> +
> >>> +               val = jiffies_to_nsecs(val);
> >>> +               val += i915->pmu.sample[__I915_SAMPLE_RC6].cur;
> >>> +               i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val;
> >>> +
> >>> +               if (!locked)
> >>> +                       spin_unlock_irqrestore(&i915->pmu.lock, flags);
> >>> +       }
> >>> +
> >>> +       return val;
> >>> +}
> >>
> >> I feel slightly dirty, but the dance checks out.
> > 
> > Would it be possible to add an RPM helper that provides the device's
> > runtime suspend residency for the above purpose? This would be
> > essentially what rtpm_suspended_time_show() provides.
> 
> That would indeed be much better since fishing into internals like the 
> above is not very nice.
> 
> However, it would also be good not to delay this fix for too long by 
> additional logistics, and keep it self-contained - easy to backport.

Ok, I've failed to find any suggestion that is an improvement on the
above. (Except suspended_jiffies_last needs only the pmu.lock, and then
move the kdev->power interaction to its own function, say
device_suspended_since()? But can't solve the locked? recursion.)

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris
Wysocki, Rafael J Feb. 7, 2018, 2:06 p.m. UTC | #3
On 2/6/2018 10:54 PM, Imre Deak wrote:
> Hi Rafael,
>
> On Tue, Feb 06, 2018 at 09:11:02PM +0000, Chris Wilson wrote:
>> Quoting Tvrtko Ursulin (2018-02-06 18:33:11)
>>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>
>>> We are not allowed to call intel_runtime_pm_get from the PMU counter read
>>> callback since the former can sleep, and the latter is running under IRQ
>>> context.
>>>
>>> To workaround this, we record the last known RC6 and while runtime
>>> suspended estimate its increase by querying the runtime PM core
>>> timestamps.
>>>
>>> Downside of this approach is that we can temporarily lose a chunk of RC6
>>> time, from the last PMU read-out to runtime suspend entry, but that will
>>> eventually catch up, once device comes back online and in the presence of
>>> PMU queries.
>>>
>>> Also, we have to be careful not to overshoot the RC6 estimate, so once
>>> resumed after a period of approximation, we only update the counter once
>>> it catches up. With the observation that RC6 is increasing while the
>>> device is suspended, this should not pose a problem and can only cause
>>> slight inaccuracies due clock base differences.
>>>
>>> v2: Simplify by estimating on top of PM core counters. (Imre)
>>>
>>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104943
>>> Fixes: 6060b6aec03c ("drm/i915/pmu: Add RC6 residency metrics")
>>> Testcase: igt/perf_pmu/rc6-runtime-pm
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Imre Deak <imre.deak@intel.com>
>>> Cc: Jani Nikula <jani.nikula@linux.intel.com>
>>> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
>>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>>> Cc: David Airlie <airlied@linux.ie>
>>> Cc: intel-gfx@lists.freedesktop.org
>>> Cc: dri-devel@lists.freedesktop.org
>>> ---
>>>   drivers/gpu/drm/i915/i915_pmu.c | 93 ++++++++++++++++++++++++++++++++++-------
>>>   drivers/gpu/drm/i915/i915_pmu.h |  6 +++
>>>   2 files changed, 84 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
>>> index 1c440460255d..bfc402d47609 100644
>>> --- a/drivers/gpu/drm/i915/i915_pmu.c
>>> +++ b/drivers/gpu/drm/i915/i915_pmu.c
>>> @@ -415,7 +415,81 @@ static int i915_pmu_event_init(struct perf_event *event)
>>>          return 0;
>>>   }
>>>   
>>> -static u64 __i915_pmu_event_read(struct perf_event *event)
>>> +static u64 get_rc6(struct drm_i915_private *i915, bool locked)
>>> +{
>>> +       unsigned long flags;
>>> +       u64 val;
>>> +
>>> +       if (intel_runtime_pm_get_if_in_use(i915)) {
>>> +               val = intel_rc6_residency_ns(i915, IS_VALLEYVIEW(i915) ?
>>> +                                                  VLV_GT_RENDER_RC6 :
>>> +                                                  GEN6_GT_GFX_RC6);
>>> +
>>> +               if (HAS_RC6p(i915))
>>> +                       val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6p);
>>> +
>>> +               if (HAS_RC6pp(i915))
>>> +                       val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6pp);
>>> +
>>> +               intel_runtime_pm_put(i915);
>>> +
>>> +               /*
>>> +                * If we are coming back from being runtime suspended we must
>>> +                * be careful not to report a larger value than returned
>>> +                * previously.
>>> +                */
>>> +
>>> +               if (!locked)
>>> +                       spin_lock_irqsave(&i915->pmu.lock, flags);
>>> +
>>> +               if (val >= i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur) {
>>> +                       i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = 0;
>>> +                       i915->pmu.sample[__I915_SAMPLE_RC6].cur = val;
>>> +               } else {
>>> +                       val = i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur;
>>> +               }
>>> +
>>> +               if (!locked)
>>> +                       spin_unlock_irqrestore(&i915->pmu.lock, flags);
>>> +       } else {
>>> +               struct pci_dev *pdev = i915->drm.pdev;
>>> +               struct device *kdev = &pdev->dev;
>>> +               unsigned long flags2;
>>> +
>>> +               /*
>>> +                * We are runtime suspended.
>>> +                *
>>> +                * Report the delta from when the device was suspended to now,
>>> +                * on top of the last known real value, as the approximated RC6
>>> +                * counter value.
>>> +                */
>>> +               if (!locked)
>>> +                       spin_lock_irqsave(&i915->pmu.lock, flags);
>>> +
>>> +               spin_lock_irqsave(&kdev->power.lock, flags2);
>>> +
>>> +               if (!i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur)
>>> +                       i915->pmu.suspended_jiffies_last =
>>> +                                               kdev->power.suspended_jiffies;
>>> +
>>> +               val = kdev->power.suspended_jiffies -
>>> +                     i915->pmu.suspended_jiffies_last;
>>> +               val += jiffies - kdev->power.accounting_timestamp;
>>> +
>>> +               spin_unlock_irqrestore(&kdev->power.lock, flags2);
>>> +
>>> +               val = jiffies_to_nsecs(val);
>>> +               val += i915->pmu.sample[__I915_SAMPLE_RC6].cur;
>>> +               i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val;
>>> +
>>> +               if (!locked)
>>> +                       spin_unlock_irqrestore(&i915->pmu.lock, flags);
>>> +       }
>>> +
>>> +       return val;
>>> +}
>> I feel slightly dirty, but the dance checks out.
> Would it be possible to add an RPM helper that provides the device's
> runtime suspend residency for the above purpose? This would be
> essentially what rtpm_suspended_time_show() provides.

Yes, in general, but as already mentioned in this thread, I guess it's 
better to do that later as an extra step for the backportability sake.

Thanks,
Rafael
diff mbox

Patch

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index 1c440460255d..bfc402d47609 100644
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -415,7 +415,81 @@  static int i915_pmu_event_init(struct perf_event *event)
 	return 0;
 }
 
-static u64 __i915_pmu_event_read(struct perf_event *event)
+static u64 get_rc6(struct drm_i915_private *i915, bool locked)
+{
+	unsigned long flags;
+	u64 val;
+
+	if (intel_runtime_pm_get_if_in_use(i915)) {
+		val = intel_rc6_residency_ns(i915, IS_VALLEYVIEW(i915) ?
+						   VLV_GT_RENDER_RC6 :
+						   GEN6_GT_GFX_RC6);
+
+		if (HAS_RC6p(i915))
+			val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6p);
+
+		if (HAS_RC6pp(i915))
+			val += intel_rc6_residency_ns(i915, GEN6_GT_GFX_RC6pp);
+
+		intel_runtime_pm_put(i915);
+
+		/*
+		 * If we are coming back from being runtime suspended we must
+		 * be careful not to report a larger value than returned
+		 * previously.
+		 */
+
+		if (!locked)
+			spin_lock_irqsave(&i915->pmu.lock, flags);
+
+		if (val >= i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur) {
+			i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = 0;
+			i915->pmu.sample[__I915_SAMPLE_RC6].cur = val;
+		} else {
+			val = i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur;
+		}
+
+		if (!locked)
+			spin_unlock_irqrestore(&i915->pmu.lock, flags);
+	} else {
+		struct pci_dev *pdev = i915->drm.pdev;
+		struct device *kdev = &pdev->dev;
+		unsigned long flags2;
+
+		/*
+		 * We are runtime suspended.
+		 *
+		 * Report the delta from when the device was suspended to now,
+		 * on top of the last known real value, as the approximated RC6
+		 * counter value.
+		 */
+		if (!locked)
+			spin_lock_irqsave(&i915->pmu.lock, flags);
+
+		spin_lock_irqsave(&kdev->power.lock, flags2);
+
+		if (!i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur)
+			i915->pmu.suspended_jiffies_last =
+						kdev->power.suspended_jiffies;
+
+		val = kdev->power.suspended_jiffies -
+		      i915->pmu.suspended_jiffies_last;
+		val += jiffies - kdev->power.accounting_timestamp;
+
+		spin_unlock_irqrestore(&kdev->power.lock, flags2);
+
+		val = jiffies_to_nsecs(val);
+		val += i915->pmu.sample[__I915_SAMPLE_RC6].cur;
+		i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val;
+
+		if (!locked)
+			spin_unlock_irqrestore(&i915->pmu.lock, flags);
+	}
+
+	return val;
+}
+
+static u64 __i915_pmu_event_read(struct perf_event *event, bool locked)
 {
 	struct drm_i915_private *i915 =
 		container_of(event->pmu, typeof(*i915), pmu.base);
@@ -453,18 +527,7 @@  static u64 __i915_pmu_event_read(struct perf_event *event)
 			val = count_interrupts(i915);
 			break;
 		case I915_PMU_RC6_RESIDENCY:
-			intel_runtime_pm_get(i915);
-			val = intel_rc6_residency_ns(i915,
-						     IS_VALLEYVIEW(i915) ?
-						     VLV_GT_RENDER_RC6 :
-						     GEN6_GT_GFX_RC6);
-			if (HAS_RC6p(i915))
-				val += intel_rc6_residency_ns(i915,
-							      GEN6_GT_GFX_RC6p);
-			if (HAS_RC6pp(i915))
-				val += intel_rc6_residency_ns(i915,
-							      GEN6_GT_GFX_RC6pp);
-			intel_runtime_pm_put(i915);
+			val = get_rc6(i915, locked);
 			break;
 		}
 	}
@@ -479,7 +542,7 @@  static void i915_pmu_event_read(struct perf_event *event)
 
 again:
 	prev = local64_read(&hwc->prev_count);
-	new = __i915_pmu_event_read(event);
+	new = __i915_pmu_event_read(event, false);
 
 	if (local64_cmpxchg(&hwc->prev_count, prev, new) != prev)
 		goto again;
@@ -534,7 +597,7 @@  static void i915_pmu_enable(struct perf_event *event)
 	 * for all listeners. Even when the event was already enabled and has
 	 * an existing non-zero value.
 	 */
-	local64_set(&event->hw.prev_count, __i915_pmu_event_read(event));
+	local64_set(&event->hw.prev_count, __i915_pmu_event_read(event, true));
 
 	spin_unlock_irqrestore(&i915->pmu.lock, flags);
 }
diff --git a/drivers/gpu/drm/i915/i915_pmu.h b/drivers/gpu/drm/i915/i915_pmu.h
index 5a2e013a56bb..aa1b1a987ea1 100644
--- a/drivers/gpu/drm/i915/i915_pmu.h
+++ b/drivers/gpu/drm/i915/i915_pmu.h
@@ -27,6 +27,8 @@ 
 enum {
 	__I915_SAMPLE_FREQ_ACT = 0,
 	__I915_SAMPLE_FREQ_REQ,
+	__I915_SAMPLE_RC6,
+	__I915_SAMPLE_RC6_ESTIMATED,
 	__I915_NUM_PMU_SAMPLERS
 };
 
@@ -94,6 +96,10 @@  struct i915_pmu {
 	 * struct intel_engine_cs.
 	 */
 	struct i915_pmu_sample sample[__I915_NUM_PMU_SAMPLERS];
+	/**
+	 * @suspended_jiffies_last: Cached suspend time from PM core.
+	 */
+	unsigned long suspended_jiffies_last;
 	/**
 	 * @i915_attr: Memory block holding device attributes.
 	 */