[Intel-gfx] [PATCH 1/8] drm/i915: Added is_intel_rpm_allowed helper

Wed Sep 28 12:31:24 UTC 2022

+

> -----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 ).
> 
> 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
> > > >