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

Jani Nikula
2015-03-13T12:36:48Z

On Thu, 12 Mar 2015, Matt Roper <matthew.d.roper@intel.com> wrote:
> 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>

Pushed to drm-intel-fixes, thanks for the patch and review.

BR,
Jani.

>
>
> 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

--
Jani Nikula, Intel Open Source Technology Center