diff mbox series

drm/i915/pps: Reuse POWER_DOMAIN_DISPLAY_CORE in pps_{lock, unlock}

Message ID 20210107112500.16216-1-anshuman.gupta@intel.com (mailing list archive)
State New, archived
Headers show
Series drm/i915/pps: Reuse POWER_DOMAIN_DISPLAY_CORE in pps_{lock, unlock} | expand

Commit Message

Anshuman Gupta Jan. 7, 2021, 11:25 a.m. UTC
We need a power_domain wakeref in pps_{lock,unlock} to prevent
a race while resetting pps state in intel_power_sequencer_reset().

intel_power_sequencer_reset() need a pps_mutex to access pps_pipe
but it can't grab pps_mutex due to deadlock with power_well
functions are called while holding pps_mutex.
intel_power_sequencer_reset() is called by power_well function
associated with legacy platforms like vlv and chv therefore re-use
the POWER_DOMAIN_DISPLAY_CORE power domain, which only used
by vlv and chv display power domain.

This will avoids the unnecessary noise of unrelated power wells
in pps_{lock,unlock}.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

Comments

Jani Nikula Jan. 8, 2021, 9:38 a.m. UTC | #1
On Thu, 07 Jan 2021, Anshuman Gupta <anshuman.gupta@intel.com> wrote:
> We need a power_domain wakeref in pps_{lock,unlock} to prevent
> a race while resetting pps state in intel_power_sequencer_reset().
>
> intel_power_sequencer_reset() need a pps_mutex to access pps_pipe
> but it can't grab pps_mutex due to deadlock with power_well
> functions are called while holding pps_mutex.
> intel_power_sequencer_reset() is called by power_well function
> associated with legacy platforms like vlv and chv therefore re-use
> the POWER_DOMAIN_DISPLAY_CORE power domain, which only used
> by vlv and chv display power domain.
>
> This will avoids the unnecessary noise of unrelated power wells
> in pps_{lock,unlock}.
>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Imre Deak <imre.deak@intel.com>
> Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>

Imre convinced me yesterday on irc that this should work.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

On the surface, this reduces the need to enable/disable the aux power so
much. It's unnecessary, so it stands to reason to optimize it. We should
only grab the domain references we actually need.

However, this *also* papers over an issue we've been seeing [1]. We need
to be aware the root cause for that remains unknown, and needs to be
figured out.

I presume simply doing aux transfers won't reproduce the problem,
because that disables the power asynchronously since commit f39194a7a8b9
("drm/i915: Disable power asynchronously during DP AUX
transfers"). Perhaps we wouldn't have seen this at all if pps_unlock()
also did that as suggested in the commit message.

Anyway, I'd like to get acks or rb's from Imre and Ville before merging
this.


BR,
Jani.


[1] http://lore.kernel.org/r/20201204081845.26528-1-anshuman.gupta@intel.com


> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 8a00e609085f..4f190a82d4ad 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -895,9 +895,7 @@ pps_lock(struct intel_dp *intel_dp)
>  	 * See intel_power_sequencer_reset() why we need
>  	 * a power domain reference here.
>  	 */
> -	wakeref = intel_display_power_get(dev_priv,
> -					  intel_aux_power_domain(dp_to_dig_port(intel_dp)));
> -
> +	wakeref = intel_display_power_get(dev_priv, POWER_DOMAIN_DISPLAY_CORE);
>  	mutex_lock(&dev_priv->pps_mutex);
>  
>  	return wakeref;
> @@ -909,9 +907,7 @@ pps_unlock(struct intel_dp *intel_dp, intel_wakeref_t wakeref)
>  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
>  
>  	mutex_unlock(&dev_priv->pps_mutex);
> -	intel_display_power_put(dev_priv,
> -				intel_aux_power_domain(dp_to_dig_port(intel_dp)),
> -				wakeref);
> +	intel_display_power_put(dev_priv, POWER_DOMAIN_DISPLAY_CORE, wakeref);
>  	return 0;
>  }
Imre Deak Jan. 8, 2021, 2:33 p.m. UTC | #2
On Fri, Jan 08, 2021 at 11:38:04AM +0200, Jani Nikula wrote:
> On Thu, 07 Jan 2021, Anshuman Gupta <anshuman.gupta@intel.com> wrote:
> > We need a power_domain wakeref in pps_{lock,unlock} to prevent
> > a race while resetting pps state in intel_power_sequencer_reset().
> >
> > intel_power_sequencer_reset() need a pps_mutex to access pps_pipe
> > but it can't grab pps_mutex due to deadlock with power_well
> > functions are called while holding pps_mutex.
> > intel_power_sequencer_reset() is called by power_well function
> > associated with legacy platforms like vlv and chv therefore re-use
> > the POWER_DOMAIN_DISPLAY_CORE power domain, which only used
> > by vlv and chv display power domain.
> >
> > This will avoids the unnecessary noise of unrelated power wells
> > in pps_{lock,unlock}.
> >
> > Cc: Jani Nikula <jani.nikula@intel.com>
> > Cc: Imre Deak <imre.deak@intel.com>
> > Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
> 
> Imre convinced me yesterday on irc that this should work.
> 
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
> 
> On the surface, this reduces the need to enable/disable the aux power so
> much. It's unnecessary, so it stands to reason to optimize it. We should
> only grab the domain references we actually need.
> 
> However, this *also* papers over an issue we've been seeing [1]. We need
> to be aware the root cause for that remains unknown, and needs to be
> figured out.
> 
> I presume simply doing aux transfers won't reproduce the problem,
> because that disables the power asynchronously since commit f39194a7a8b9
> ("drm/i915: Disable power asynchronously during DP AUX
> transfers"). Perhaps we wouldn't have seen this at all if pps_unlock()
> also did that as suggested in the commit message.
> 
> Anyway, I'd like to get acks or rb's from Imre and Ville before merging
> this.

Looks ok to me:
Acked-by: Imre Deak <imre.deak@intel.com>

> 
> 
> BR,
> Jani.
> 
> 
> [1] http://lore.kernel.org/r/20201204081845.26528-1-anshuman.gupta@intel.com
> 
> 
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 8 ++------
> >  1 file changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 8a00e609085f..4f190a82d4ad 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -895,9 +895,7 @@ pps_lock(struct intel_dp *intel_dp)
> >  	 * See intel_power_sequencer_reset() why we need
> >  	 * a power domain reference here.
> >  	 */
> > -	wakeref = intel_display_power_get(dev_priv,
> > -					  intel_aux_power_domain(dp_to_dig_port(intel_dp)));
> > -
> > +	wakeref = intel_display_power_get(dev_priv, POWER_DOMAIN_DISPLAY_CORE);
> >  	mutex_lock(&dev_priv->pps_mutex);
> >  
> >  	return wakeref;
> > @@ -909,9 +907,7 @@ pps_unlock(struct intel_dp *intel_dp, intel_wakeref_t wakeref)
> >  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> >  
> >  	mutex_unlock(&dev_priv->pps_mutex);
> > -	intel_display_power_put(dev_priv,
> > -				intel_aux_power_domain(dp_to_dig_port(intel_dp)),
> > -				wakeref);
> > +	intel_display_power_put(dev_priv, POWER_DOMAIN_DISPLAY_CORE, wakeref);
> >  	return 0;
> >  }
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center
Jani Nikula Jan. 8, 2021, 4:40 p.m. UTC | #3
On Fri, 08 Jan 2021, Imre Deak <imre.deak@intel.com> wrote:
> On Fri, Jan 08, 2021 at 11:38:04AM +0200, Jani Nikula wrote:
>> On Thu, 07 Jan 2021, Anshuman Gupta <anshuman.gupta@intel.com> wrote:
>> > We need a power_domain wakeref in pps_{lock,unlock} to prevent
>> > a race while resetting pps state in intel_power_sequencer_reset().
>> >
>> > intel_power_sequencer_reset() need a pps_mutex to access pps_pipe
>> > but it can't grab pps_mutex due to deadlock with power_well
>> > functions are called while holding pps_mutex.
>> > intel_power_sequencer_reset() is called by power_well function
>> > associated with legacy platforms like vlv and chv therefore re-use
>> > the POWER_DOMAIN_DISPLAY_CORE power domain, which only used
>> > by vlv and chv display power domain.
>> >
>> > This will avoids the unnecessary noise of unrelated power wells
>> > in pps_{lock,unlock}.
>> >
>> > Cc: Jani Nikula <jani.nikula@intel.com>
>> > Cc: Imre Deak <imre.deak@intel.com>
>> > Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
>> 
>> Imre convinced me yesterday on irc that this should work.
>> 
>> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
>> 
>> On the surface, this reduces the need to enable/disable the aux power so
>> much. It's unnecessary, so it stands to reason to optimize it. We should
>> only grab the domain references we actually need.
>> 
>> However, this *also* papers over an issue we've been seeing [1]. We need
>> to be aware the root cause for that remains unknown, and needs to be
>> figured out.
>> 
>> I presume simply doing aux transfers won't reproduce the problem,
>> because that disables the power asynchronously since commit f39194a7a8b9
>> ("drm/i915: Disable power asynchronously during DP AUX
>> transfers"). Perhaps we wouldn't have seen this at all if pps_unlock()
>> also did that as suggested in the commit message.
>> 
>> Anyway, I'd like to get acks or rb's from Imre and Ville before merging
>> this.
>
> Looks ok to me:
> Acked-by: Imre Deak <imre.deak@intel.com>

Thanks, pushed to din.

BR,
Jani.


>
>> 
>> 
>> BR,
>> Jani.
>> 
>> 
>> [1] http://lore.kernel.org/r/20201204081845.26528-1-anshuman.gupta@intel.com
>> 
>> 
>> > ---
>> >  drivers/gpu/drm/i915/display/intel_dp.c | 8 ++------
>> >  1 file changed, 2 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> > index 8a00e609085f..4f190a82d4ad 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> > @@ -895,9 +895,7 @@ pps_lock(struct intel_dp *intel_dp)
>> >  	 * See intel_power_sequencer_reset() why we need
>> >  	 * a power domain reference here.
>> >  	 */
>> > -	wakeref = intel_display_power_get(dev_priv,
>> > -					  intel_aux_power_domain(dp_to_dig_port(intel_dp)));
>> > -
>> > +	wakeref = intel_display_power_get(dev_priv, POWER_DOMAIN_DISPLAY_CORE);
>> >  	mutex_lock(&dev_priv->pps_mutex);
>> >  
>> >  	return wakeref;
>> > @@ -909,9 +907,7 @@ pps_unlock(struct intel_dp *intel_dp, intel_wakeref_t wakeref)
>> >  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
>> >  
>> >  	mutex_unlock(&dev_priv->pps_mutex);
>> > -	intel_display_power_put(dev_priv,
>> > -				intel_aux_power_domain(dp_to_dig_port(intel_dp)),
>> > -				wakeref);
>> > +	intel_display_power_put(dev_priv, POWER_DOMAIN_DISPLAY_CORE, wakeref);
>> >  	return 0;
>> >  }
>> 
>> -- 
>> Jani Nikula, Intel Open Source Graphics Center
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 8a00e609085f..4f190a82d4ad 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -895,9 +895,7 @@  pps_lock(struct intel_dp *intel_dp)
 	 * See intel_power_sequencer_reset() why we need
 	 * a power domain reference here.
 	 */
-	wakeref = intel_display_power_get(dev_priv,
-					  intel_aux_power_domain(dp_to_dig_port(intel_dp)));
-
+	wakeref = intel_display_power_get(dev_priv, POWER_DOMAIN_DISPLAY_CORE);
 	mutex_lock(&dev_priv->pps_mutex);
 
 	return wakeref;
@@ -909,9 +907,7 @@  pps_unlock(struct intel_dp *intel_dp, intel_wakeref_t wakeref)
 	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
 
 	mutex_unlock(&dev_priv->pps_mutex);
-	intel_display_power_put(dev_priv,
-				intel_aux_power_domain(dp_to_dig_port(intel_dp)),
-				wakeref);
+	intel_display_power_put(dev_priv, POWER_DOMAIN_DISPLAY_CORE, wakeref);
 	return 0;
 }