Re: [PATCH 14/24] drm/i915: Add dev_priv->wm.mutex

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 23, 2014 at 06:47:04PM -0300, Paulo Zanoni wrote:
> 2014-03-07 13:32 GMT-03:00  <ville.syrjala@linux.intel.com>:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > Add a mutex to protect most of the watermark state. Will be useful when
> > we start to update watermarks asynchronously from plane updates, or
> > when we get finer grained locking for planes.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.h  | 11 ++++++++++-
> >  drivers/gpu/drm/i915/intel_drv.h |  5 ++++-
> >  drivers/gpu/drm/i915/intel_pm.c  | 21 +++++++++++++++++++--
> >  3 files changed, 33 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 29da39f..0b19723 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -1595,8 +1595,17 @@ typedef struct drm_i915_private {
> >                 /* cursor */
> >                 uint16_t cur_latency[5];
> >
> > -               /* current hardware state */
> > +               /*
> > +                * current hardware state
> > +                * protected by dev_priv->wm.mutex
> > +                */
> >                 struct ilk_wm_values hw;
> > +
> > +               /*
> > +                * protects some dev_priv->wm and intel_crtc->wm
> > +                * state as well as the actual hardware registers
> > +                */
> > +               struct mutex mutex;
> >         } wm;
> >
> >         struct i915_package_c8 pc8;
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index f022a78..8e32d69 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -384,7 +384,10 @@ struct intel_crtc {
> >
> >         /* per-pipe watermark state */
> >         struct {
> > -               /* watermarks currently being used  */
> > +               /*
> > +                * watermarks currently being used
> > +                * protected by dev_priv->wm.mutex
> > +                */
> >                 struct intel_pipe_wm active;
> >         } wm;
> >
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index 3f5c1dc..d8adcb3 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -2692,8 +2692,13 @@ static void ilk_write_wm_values(struct drm_i915_private *dev_priv,
> >  static bool ilk_disable_lp_wm(struct drm_device *dev)
> >  {
> >         struct drm_i915_private *dev_priv = dev->dev_private;
> > +       bool changed;
> >
> > -       return _ilk_disable_lp_wm(dev_priv, WM_DIRTY_LP_ALL);
> > +       mutex_lock(&dev_priv->wm.mutex);
> > +       changed = _ilk_disable_lp_wm(dev_priv, WM_DIRTY_LP_ALL);
> > +       mutex_unlock(&dev_priv->wm.mutex);
> > +
> > +       return changed;
> >  }
> >
> >  static void ilk_program_watermarks(struct drm_device *dev)
> > @@ -2733,6 +2738,7 @@ static void ilk_update_wm(struct drm_crtc *crtc)
> >  {
> >         struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> >         struct drm_device *dev = crtc->dev;
> > +       struct drm_i915_private *dev_priv = dev->dev_private;
> >         struct ilk_pipe_wm_parameters params = {};
> >         struct intel_pipe_wm pipe_wm = {};
> >
> > @@ -2740,12 +2746,17 @@ static void ilk_update_wm(struct drm_crtc *crtc)
> >
> >         intel_compute_pipe_wm(crtc, &params, &pipe_wm);
> >
> > +       mutex_lock(&dev_priv->wm.mutex);
> > +
> >         if (!memcmp(&intel_crtc->wm.active, &pipe_wm, sizeof(pipe_wm)))
> > -               return;
> > +               goto unlock;
> >
> >         intel_crtc->wm.active = pipe_wm;
> >
> >         ilk_program_watermarks(dev);
> > +
> > + unlock:
> > +       mutex_unlock(&dev_priv->wm.mutex);
> >  }
> >
> >  static void ilk_update_sprite_wm(struct drm_plane *plane,
> > @@ -2817,10 +2828,14 @@ void ilk_wm_get_hw_state(struct drm_device *dev)
> >         struct drm_i915_private *dev_priv = dev->dev_private;
> >         struct drm_crtc *crtc;
> >
> > +       mutex_lock(&dev_priv->wm.mutex);
> > +
> >         _ilk_wm_get_hw_state(dev, &dev_priv->wm.hw);
> >
> >         list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
> >                 _ilk_pipe_wm_hw_to_sw(crtc);
> > +
> > +       mutex_unlock(&dev_priv->wm.mutex);
> >  }
> >
> >  /**
> > @@ -5760,6 +5775,8 @@ void intel_init_pm(struct drm_device *dev)
> >  {
> >         struct drm_i915_private *dev_priv = dev->dev_private;
> >
> > +       mutex_init(&dev_priv->wm.mutex);
> > +
> 
> I think you should probably init this at intel_pm_setup(), which is
> called way earlier. Just to be safe.

If we call some WM function before intel_init_pm() we have a serious
bug. This is where we set up the WM function pointers and extract the
latency values from SSKPD/MLTR.

> 
> With that fixed: Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>.
> 
> >         if (HAS_FBC(dev)) {
> >                 if (INTEL_INFO(dev)->gen >= 7) {
> >                         dev_priv->display.fbc_enabled = ironlake_fbc_enabled;
> > --
> > 1.8.3.2
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> 
> 
> -- 
> Paulo Zanoni

-- 
Ville Syrjälä
Intel OTC