Re: [PATCH] drm/i915: Ensure plane->state->fb stays in sync with plane->fb

[Matt Roper <matthew.d.roper@intel.com>]

On Thu, Mar 12, 2015 at 02:45:31PM +0200, Jani Nikula wrote:
> 
> Matt, please review or suggest an alternative for v4.0-rc.
> 
> Thanks,
> Jani.

Yep, this looks good to me.  So

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>


Matt

> 
> 
> On Thu, 12 Mar 2015, Xi Ruoyao <xry111@outlook.com> wrote:
> > plane->state->fb and plane->fb should always reference the same FB so
> > that atomic and legacy codepaths have the same view of display state.
> > However, there are some places in kernel code that directly set
> > plane->fb and neglect to update plane->state->fb. If we never do a
> > successful update through the atomic pipeline, the RmFB cleanup code
> > will look at the plane->state->fb pointer, which has never actually
> > been set to a legitimate value, and try to clean it up, leading to
> > BUG's.
> >
> > Add a quick helper function to synchronize plane->state->fb with
> > plane->fb and call it everywhere the driver tries to manually set
> > plane->fb outside of the atomic pipeline. In this function, use
> > drm_atomic_set_fb_for_plane instead of writing plane->state->fb
> > directly to keep the reference count right.
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88909
> > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=93711
> > Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Signed-off-by: Xi Ruoyao <xry111@outlook.com>
> > ---
> >  This is modified from Matt Roper's patch to drm-intel-nightly with 
> >  commit id
> >
> >  	afd65eb4cc0578a9c07d621acdb8a570e2782bf7
> >
> >  However this bug exists in mainline kernel too, so I created this to
> >  fix it in mainline kernel.
> >
> >  A minor change is to use drm_atomic_set_fb_for_plane instead of
> >  update reference count manually.
> >
> >  drivers/gpu/drm/i915/intel_display.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index e730789..c483f2f 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -37,6 +37,7 @@
> >  #include <drm/i915_drm.h>
> >  #include "i915_drv.h"
> >  #include "i915_trace.h"
> > +#include <drm/drm_atomic.h>
> >  #include <drm/drm_atomic_helper.h>
> >  #include <drm/drm_dp_helper.h>
> >  #include <drm/drm_crtc_helper.h>
> > @@ -2416,6 +2417,14 @@ out_unref_obj:
> >  	return false;
> >  }
> >  
> > +/* Update plane->state->fb to match plane->fb after driver-internal updates */
> > +static void
> > +update_state_fb(struct drm_plane *plane)
> > +{
> > +	if (plane->fb != plane->state->fb)
> > +		drm_atomic_set_fb_for_plane(plane->state, plane->fb);
> > +}
> > +
> >  static void
> >  intel_find_plane_obj(struct intel_crtc *intel_crtc,
> >  		     struct intel_initial_plane_config *plane_config)
> > @@ -2462,6 +2471,8 @@ intel_find_plane_obj(struct intel_crtc *intel_crtc,
> >  			break;
> >  		}
> >  	}
> > +
> > +	update_state_fb(intel_crtc->base.primary);
> >  }
> >  
> >  static void i9xx_update_primary_plane(struct drm_crtc *crtc,
> > @@ -6650,6 +6661,7 @@ i9xx_get_initial_plane_config(struct intel_crtc *crtc,
> >  		      plane_config->size);
> >  
> >  	crtc->base.primary->fb = fb;
> > +	update_state_fb(crtc->base.primary);
> >  }
> >  
> >  static void chv_crtc_clock_get(struct intel_crtc *crtc,
> > @@ -7687,6 +7699,7 @@ skylake_get_initial_plane_config(struct intel_crtc *crtc,
> >  		      plane_config->size);
> >  
> >  	crtc->base.primary->fb = fb;
> > +	update_state_fb(crtc->base.primary);
> >  	return;
> >  
> >  error:
> > @@ -7778,6 +7791,7 @@ ironlake_get_initial_plane_config(struct intel_crtc *crtc,
> >  		      plane_config->size);
> >  
> >  	crtc->base.primary->fb = fb;
> > +	update_state_fb(crtc->base.primary);
> >  }
> >  
> >  static bool ironlake_get_pipe_config(struct intel_crtc *crtc,
> > @@ -9816,6 +9830,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
> >  	drm_gem_object_reference(&obj->base);
> >  
> >  	crtc->primary->fb = fb;
> > +	update_state_fb(crtc->primary);
> >  
> >  	work->pending_flip_obj = obj;
> >  
> > @@ -9884,6 +9899,7 @@ cleanup_unpin:
> >  cleanup_pending:
> >  	atomic_dec(&intel_crtc->unpin_work_count);
> >  	crtc->primary->fb = old_fb;
> > +	update_state_fb(crtc->primary);
> >  	drm_gem_object_unreference(&work->old_fb_obj->base);
> >  	drm_gem_object_unreference(&obj->base);
> >  	mutex_unlock(&dev->struct_mutex);
> > @@ -13718,6 +13734,7 @@ void intel_modeset_gem_init(struct drm_device *dev)
> >  				  to_intel_crtc(c)->pipe);
> >  			drm_framebuffer_unreference(c->primary->fb);
> >  			c->primary->fb = NULL;
> > +			update_state_fb(c->primary);
> >  		}
> >  	}
> >  	mutex_unlock(&dev->struct_mutex);
> > -- 
> > 1.9.1
> >
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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