[PATCH v2 1/2] drm/i915/display: Add own counter for Panel Replay vblank workaround

[Hogander, Jouni]

On Thu, 2024-10-10 at 16:22 +0300, Jani Nikula wrote:
> On Thu, 10 Oct 2024, "Hogander, Jouni" <jouni.hogander at intel.com>
> wrote:
> > On Wed, 2024-10-09 at 17:15 +0300, Jani Nikula wrote:
> > > On Wed, 09 Oct 2024, Jouni Högander <jouni.hogander at intel.com>
> > > wrote:
> > > > We are about to change meaning of vblank_enabled to fix Panel
> > > > Replay vblank
> > > > workaround. For sake of clarity we need to rename it.
> > > > Vblank_enabled is
> > > > used for i915gm/i945gm vblank irq workaround as well -> instead
> > > > of
> > > > rename
> > > > add new counter named as vblank_wa_pipes.
> > > > 
> > > > v2:
> > > >   - s/vblank_wa_pipes/vblank_wa_num_pipes/
> > > >   - use int as a type for the counter
> > > > 
> > > > Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/display/intel_display_core.h | 2 ++
> > > >  drivers/gpu/drm/i915/display/intel_display_irq.c  | 8 ++++----
> > > >  2 files changed, 6 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h
> > > > b/drivers/gpu/drm/i915/display/intel_display_core.h
> > > > index 982dd9469195..45697af25fa9 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_display_core.h
> > > > +++ b/drivers/gpu/drm/i915/display/intel_display_core.h
> > > > @@ -455,6 +455,8 @@ struct intel_display {
> > > >                 /* For i915gm/i945gm vblank irq workaround */
> > > >                 u8 vblank_enabled;
> > > 
> > > Maybe we want to rename this one too?
> > 
> > I tried to explain it in commit message. Seems I didn't succeed in
> > it.
> > 
> > vblank_enabled is currently used by two workarounds:
> > 
> > 1. i915gm/i945gm vblank irq workaround
> > 2. LNL Panel Replay vblank workaround
> > 
> > 1. and 2. are currently using vblank_enabled in a way they are
> > respecting it's meaning: is vblank enabled/disabled.
> 
> Crucially, they're both using the same member, but never on the same
> platform. The member is "overloaded" for two different things. (See
> the
> otherwise unrelated series [1], it's the same thing with sb_lock.)
> 
> > It was found out that 2. as it is implemented currently doesn't
> > work
> > properly. Instead of information on vblank enabled/disabled we need
> > to
> > know if there are pipes that need the workaround.
> > 
> > Renaming vblank_enabled wouldn't reflect how it's used in 1. This
> > is
> > why I decided to add own variable for 2. and this is what this
> > patch is
> > about: Keep vblank_enabled as it is for 1. and add own variable for
> > 2.
> 
> My point is more generic, and it was not intended as a comment on
> *this*
> patch. Having a "vblank_enabled" member is misleading, when it's
> really
> just used for a very narrow case on a few platforms.
> 
> Does that make more sense?

Ok, thank you for the explanation. I decided to push current patches.
Let's take care of this separately.

BR,

Jouni Högander

> 
> 
> BR,
> Jani.
> 
> 
> [1]
> https://lore.kernel.org/r/cover.1727890136.git.jani.nikula@intel.com
> 
> > 
> > BR,
> > 
> > Jouni Högander
> >  
> > > 
> > > BR,
> > > Jani.
> > > 
> > > >  
> > > > +               int vblank_wa_num_pipes;
> > > > +
> > > >                 struct work_struct vblank_dc_work;
> > > >  
> > > >                 u32 de_irq_mask[I915_MAX_PIPES];
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_display_irq.c
> > > > b/drivers/gpu/drm/i915/display/intel_display_irq.c
> > > > index a4367ddc7a44..8226ea218d77 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_display_irq.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_display_irq.c
> > > > @@ -1424,7 +1424,7 @@ static void
> > > > intel_display_vblank_dc_work(struct work_struct *work)
> > > >         struct intel_display *display =
> > > >                 container_of(work, typeof(*display),
> > > > irq.vblank_dc_work);
> > > >         struct drm_i915_private *i915 = to_i915(display->drm);
> > > > -       u8 vblank_enabled = READ_ONCE(display-
> > > > >irq.vblank_enabled);
> > > > +       int vblank_wa_num_pipes = READ_ONCE(display-
> > > > > irq.vblank_wa_num_pipes);
> > > >  
> > > >         /*
> > > >          * NOTE: intel_display_power_set_target_dc_state is
> > > > used
> > > > only by PSR
> > > > @@ -1432,7 +1432,7 @@ static void
> > > > intel_display_vblank_dc_work(struct work_struct *work)
> > > >          * PSR code. If DC3CO is taken into use we need take
> > > > that
> > > > into account
> > > >          * here as well.
> > > >          */
> > > > -       intel_display_power_set_target_dc_state(i915,
> > > > vblank_enabled ? DC_STATE_DISABLE :
> > > > +       intel_display_power_set_target_dc_state(i915,
> > > > vblank_wa_num_pipes ? DC_STATE_DISABLE :
> > > >                                                 DC_STATE_EN_UPT
> > > > O_DC
> > > > 6);
> > > >  }
> > > >  
> > > > @@ -1447,7 +1447,7 @@ int bdw_enable_vblank(struct drm_crtc
> > > > *_crtc)
> > > >         if (gen11_dsi_configure_te(crtc, true))
> > > >                 return 0;
> > > >  
> > > > -       if (display->irq.vblank_enabled++ == 0 && crtc-
> > > > > block_dc_for_vblank)
> > > > +       if (display->irq.vblank_wa_num_pipes++ == 0 && crtc-
> > > > > block_dc_for_vblank)
> > > >                 schedule_work(&display->irq.vblank_dc_work);
> > > >  
> > > >         spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
> > > > @@ -1478,7 +1478,7 @@ void bdw_disable_vblank(struct drm_crtc
> > > > *_crtc)
> > > >         bdw_disable_pipe_irq(dev_priv, pipe, GEN8_PIPE_VBLANK);
> > > >         spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
> > > >  
> > > > -       if (--display->irq.vblank_enabled == 0 && crtc-
> > > > > block_dc_for_vblank)
> > > > +       if (--display->irq.vblank_wa_num_pipes == 0 && crtc-
> > > > > block_dc_for_vblank)
> > > >                 schedule_work(&display->irq.vblank_dc_work);
> > > >  }
> > > 
> > 
>