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

Daniel Vetter
2015-02-04T09:38:26Z

On Tue, Feb 03, 2015 at 01:10:04PM -0800, Matt Roper 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.
> In commit
>
> commit db068420560511de80ac59222644f2bdf278c3d5
> Author: Matt Roper <matthew.d.roper@intel.com>
> Date: Fri Jan 30 16:22:36 2015 -0800
>
> drm/i915: Keep plane->state updated on pageflip
>
> we already fixed one case where these two pointers could get out of
> sync. However it turns out there are a few other places (mainly dealing
> with initial FB setup at boot) 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 update reference counts accordingly) and call it
> everywhere the driver tries to manually set plane->fb outside of the
> atomic pipeline.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88909
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>

Unrelated thing I've spotted while reviewing this: We still update
plane->fb in our plane commit hooks, but helpers should take care of that.
Do we still have these because our code still looks at plane->fb instead
of plane->state->fb or is there some deeper reason?

I think a large-scale s/plane->fb/plane->state->fb/ and then removing
those and relying upon the fixup code in the helpers/core would be good.
Unfortunately we can't cocci this since we need to keep a few ...

Anyway, patch lgtm and is merged.

Thanks, Daniel
> ---
> drivers/gpu/drm/i915/intel_display.c | 29 ++++++++++++++++++++++-------
> 1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 213b870..e5c0579 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2410,6 +2410,20 @@ 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)
> + return;
> +
> + if (plane->state->fb)
> + drm_framebuffer_unreference(plane->state->fb);
> + plane->state->fb = plane->fb;
> + if (plane->state->fb)
> + drm_framebuffer_reference(plane->state->fb);
> +}
> +
> static void
> intel_find_plane_obj(struct intel_crtc *intel_crtc,
> struct intel_initial_plane_config *plane_config)
> @@ -2456,6 +2470,8 @@ 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,
> @@ -6635,6 +6651,7 @@ 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,
> @@ -7672,6 +7689,7 @@ 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:
> @@ -7763,6 +7781,7 @@ 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,
> @@ -9800,13 +9819,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
> drm_gem_object_reference(&obj->base);
>
> crtc->primary->fb = fb;
> -
> - /* Keep state structure in sync */
> - if (crtc->primary->state->fb)
> - drm_framebuffer_unreference(crtc->primary->state->fb);
> - crtc->primary->state->fb = fb;
> - if (crtc->primary->state->fb)
> - drm_framebuffer_reference(crtc->primary->state->fb);
> + update_state_fb(crtc->primary);
>
> work->pending_flip_obj = obj;
>
> @@ -9875,6 +9888,7 @@ cleanup_unpin:
> cleanup_pending:
> atomic_dec(&intel_crtc->unpin_work_count);
> crtc->primary->fb = old_fb;
> + update_state_fb(crtc->primary);
> drm_framebuffer_unreference(work->old_fb);
> drm_gem_object_unreference(&obj->base);
> mutex_unlock(&dev->struct_mutex);
> @@ -13709,6 +13723,7 @@ 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);
> --
> 1.8.5.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch