[Intel-gfx] [PATCH 1/8] drm/i915: Added is_intel_rpm_allowed helper
Vivi, Rodrigo
rodrigo.vivi at intel.com
Wed Sep 28 14:29:51 UTC 2022
On Wed, 2022-09-28 at 12:31 +0000, Tangudu, Tilak wrote:
> +
>
> > -----Original Message-----
> > From: Tangudu, Tilak
> > Sent: Wednesday, September 28, 2022 5:46 PM
> > To: Tangudu, Tilak <tilak.tangudu at intel.com>; Vivi, Rodrigo
> > <rodrigo.vivi at intel.com>; Nikula, Jani <jani.nikula at intel.com>
> > Cc: Wilson, Chris P <Chris.P.Wilson at intel.com>; Gupta, saurabhg
> > <saurabhg.gupta at intel.com>; intel-gfx at lists.freedesktop.org
> > Subject: RE: [PATCH 1/8] drm/i915: Added is_intel_rpm_allowed
> > helper
> >
> > @Nikula, Jani,
> >
> > As you know we have reused i915_gem_backup_suspend,
> > i915_gem_suspend_late and i915_gem_resume in
> > runtime_pm_suspend/resume callbacks ,they use runtime pm helpers
> > (intel_runtime_pm_get/put).
> > These need to be avoided in callbacks as they lead to deadlock.
> >
> > This can be done in two ways
> > 1) push runtime pm helpers usage at higher level functions,
> > Which requires code refactoring
> > (https://patchwork.freedesktop.org/series/105427/#rev2 is
> > partially
> > implemented following this)
> > 2) Add is_intel_rpm_allowed helper and avoid the runtime helpers
> > (https://patchwork.freedesktop.org/series/105427/#rev3 is
> > completely
> > implemented following this)
> >
> > Hope I gave you the context,
> >
> > As per your review comment in rev2, the below is implemented in
> > rev3
> >
> > """"""""""""""""""""""""
> > v2: Return -2 if runtime pm is not allowed in runtime_pm_get and
> > skip
> > wakeref release in runtime_pm_put if wakeref value is -2. - Jani N
> > Signed-off-by: Tilak Tangudu <tilak.tangudu at intel.com>
> > """""""""""""""""""""""""
> >
> > Rodrigo and myself want to trigger a discussion, if 2) is a proper
> > approach or
> > go with 1) which requires lot of code refactoring.
> > Or Is there any way we follow 1) with less code refactoring.?
> > Or Do you think there is any other proper approach ?
> >
> > (Please note rev3 is not clean, d3cold off support need to be
> > restricted to
> > Headless clients for now , we see some Display related warnings in
> > headed
> > case ).
I believe this warnings shows that the solution 2 has some flaws or
corner cases that we don't fully understand.
I honestly believe we need to go with option 1, moving the runtime_pm_
{get,put} to higher levels.
One way or another, we should not go partial here, but with full
implementation so we can see if we are really covered.
Jani, thoughts?
> >
> > Thanks
> > Tilak
> >
> >
> > > -----Original Message-----
> > > From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On
> > > Behalf Of
> > > Tangudu, Tilak
> > > Sent: Thursday, August 4, 2022 11:03 AM
> > > To: Vivi, Rodrigo <rodrigo.vivi at intel.com>
> > > Cc: Nikula, Jani <jani.nikula at intel.com>; Wilson, Chris P
> > > <chris.p.wilson at intel.com>; Gupta, saurabhg
> > > <saurabhg.gupta at intel.com>; intel-gfx at lists.freedesktop.org
> > > Subject: Re: [Intel-gfx] [PATCH 1/8] drm/i915: Added
> > > is_intel_rpm_allowed helper
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Vivi, Rodrigo <rodrigo.vivi at intel.com>
> > > > Sent: Thursday, August 4, 2022 2:01 AM
> > > > To: Tangudu, Tilak <tilak.tangudu at intel.com>
> > > > Cc: Ewins, Jon <jon.ewins at intel.com>; Belgaumkar, Vinay
> > > > <vinay.belgaumkar at intel.com>; Roper, Matthew D
> > > > <matthew.d.roper at intel.com>; Wilson, Chris P
> > > > <chris.p.wilson at intel.com>; Nikula, Jani
> > > > <jani.nikula at intel.com>;
> > > > Gupta, saurabhg <saurabhg.gupta at intel.com>; Gupta, Anshuman
> > > > <anshuman.gupta at intel.com>; Nilawar, Badal
> > > > <badal.nilawar at intel.com>; Deak, Imre <imre.deak at intel.com>;
> > > > Iddamsetty, Aravind <aravind.iddamsetty at intel.com>;
> > > > intel-gfx at lists.freedesktop.org
> > > > Subject: Re: [PATCH 1/8] drm/i915: Added is_intel_rpm_allowed
> > > > helper
> > > >
> > > > On Thu, Jul 21, 2022 at 03:29:48PM +0530,
> > > > tilak.tangudu at intel.com
> > wrote:
> > > > > From: Tilak Tangudu <tilak.tangudu at intel.com>
> > > > >
> > > > > Added is_intel_rpm_allowed function to query the runtime_pm
> > > > > status
> > > > > and disllow during suspending and resuming.
> > > >
> > > > >
> > > > > v2: Return -2 if runtime pm is not allowed in runtime_pm_get
> > > > > and
> > > > > skip wakeref release in runtime_pm_put if wakeref value is -
> > > > > 2. -
> > > > > Jani N
> > > >
> > > > Should we have some defines instead of the -#s?
> > > Ok will address this.
> > > >
> > > > > Signed-off-by: Tilak Tangudu <tilak.tangudu at intel.com>
> > > > > ---
> > > > > drivers/gpu/drm/i915/intel_runtime_pm.c | 23
> > > > ++++++++++++++++++++++-
> > > > > drivers/gpu/drm/i915/intel_runtime_pm.h | 1 +
> > > > > 2 files changed, 23 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > > > b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > > > index 6ed5786bcd29..704beeeb560b 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > > > > @@ -113,7 +113,7 @@ static void
> > > > untrack_intel_runtime_pm_wakeref(struct intel_runtime_pm *rpm,
> > > > > unsigned long flags, n;
> > > > > bool found = false;
> > > > >
> > > > > - if (unlikely(stack == -1))
> > > > > + if (unlikely(stack == -1) || unlikely(stack == -2))
> > > > > return;
> > > > >
> > > > > spin_lock_irqsave(&rpm->debug.lock, flags); @@ -320,6
> > > > > +320,21
> > > > @@
> > > > > untrack_all_intel_runtime_pm_wakerefs(struct intel_runtime_pm
> > > > > *rpm) }
> > > > >
> > > > > #endif
> > > > > +static int intel_runtime_pm_status(struct intel_runtime_pm
> > > > > *rpm) {
> > > > > + return rpm->kdev->power.runtime_status; }
> > > > > +
> > > > > +bool is_intel_rpm_allowed(struct intel_runtime_pm *rpm)
> > > >
> > > > why not static?
> > > We need is_intel_rpm_allowed for rc6 helpers , the helpers use
> > > pm_runtime_get_sync, To avoid lock issue we need to use it here
> > > too.
> > >
> > > See this patch " drm/i915: Guard rc6 helpers with
> > > is_intel_rpm_allowed"
> > >
> > > >
> > > > > +{
> > > > > + int rpm_status;
> > > > > +
> > > > > + rpm_status = intel_runtime_pm_status(rpm);
> > > > > + if (rpm_status == RPM_RESUMING
> > > >
> > > > I don't have a good feeling about this. If we are resuming we
> > > > shouldn't grab extra references... This seems a workaround for
> > > > the
> > > > lock
> > > mess.
> > > >
> > > > > > > rpm_status == RPM_SUSPENDING)
> > > >
> > > > and when we are suspending and we call this function is because
> > > > we
> > > > need to wake up, no?!
> > >
> > > As we have re-used i915_gem_backup_suspend, i915_gem_suspend_late
> > and
> > > i915_gem_resume , These functions use runtime helpers, which in-
> > > turn
> > > call runtime suspend/resume callbacks and leads to deadlock.
> > > So, these helpers need to be avoided. we have added
> > > is_intel_rpm_allowed and disallowed rpm callbacks with above
> > > condition
> > > during suspending and resuming to avoid deadlock.
> > > >
> > > > > + return false;
> > > > > + else
> > > > > + return true;
> > > > > +}
> > > > >
> > > > > static void
> > > > > intel_runtime_pm_acquire(struct intel_runtime_pm *rpm, bool
> > > > > wakelock) @@ -354,6 +369,9 @@ static intel_wakeref_t
> > > > __intel_runtime_pm_get(struct intel_runtime_pm *rpm,
> > > > >
> > > > > runtime_pm);
> > > > > int ret;
> > > > >
> > > > > + if (!is_intel_rpm_allowed(rpm))
> > > > > + return -2;
> > > > > +
> > > > > ret = pm_runtime_get_sync(rpm->kdev);
> > > > > drm_WARN_ONCE(&i915->drm, ret < 0,
> > > > > "pm_runtime_get_sync() failed: %d\n",
> > > > > ret); @@ -490,6
> > > > +508,9
> > > > > @@ static void __intel_runtime_pm_put(struct intel_runtime_pm
> > > > > *rpm,
> > > > >
> > > > > untrack_intel_runtime_pm_wakeref(rpm, wref);
> > > > >
> > > > > + if (wref == -2)
> > > > > + return;
> > > > > +
> > > > > intel_runtime_pm_release(rpm, wakelock);
> > > > >
> > > > > pm_runtime_mark_last_busy(kdev); diff --git
> > > > > a/drivers/gpu/drm/i915/intel_runtime_pm.h
> > > > > b/drivers/gpu/drm/i915/intel_runtime_pm.h
> > > > > index d9160e3ff4af..99418c3a934a 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_runtime_pm.h
> > > > > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.h
> > > > > @@ -173,6 +173,7 @@ void intel_runtime_pm_init_early(struct
> > > > > intel_runtime_pm *rpm); void intel_runtime_pm_enable(struct
> > > > > intel_runtime_pm *rpm); void intel_runtime_pm_disable(struct
> > > > > intel_runtime_pm *rpm); void
> > > > > intel_runtime_pm_driver_release(struct
> > > > > intel_runtime_pm *rpm);
> > > > > +bool is_intel_rpm_allowed(struct intel_runtime_pm *rpm);
> > > >
> > > > if really need to export please follow the naming convention.\
> > >
> > > Ok will address this.
> > >
> > > -Tilak
> > > >
> > > > >
> > > > > intel_wakeref_t intel_runtime_pm_get(struct intel_runtime_pm
> > > > > *rpm); intel_wakeref_t intel_runtime_pm_get_if_in_use(struct
> > > > > intel_runtime_pm *rpm);
> > > > > --
> > > > > 2.25.1
> > > > >
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