Re: [PATCH 5/5] drm/i915: Fix atomic state when reusing the firmware fb

Damien Lespiau
2015-02-05T18:58:08Z

On Thu, Feb 05, 2015 at 10:10:26AM -0800, Matt Roper wrote:
> On Thu, Feb 05, 2015 at 05:22:19PM +0000, Damien Lespiau wrote:
> > Right now, we get a warning when taking over the firmware fb:
> >
> > [drm:drm_atomic_plane_check] FB set but no CRTC
> >
> > with the following backtrace:
> >
> > [<ffffffffa010339d>] drm_atomic_check_only+0x35d/0x510 [drm]
> > [<ffffffffa0103567>] drm_atomic_commit+0x17/0x60 [drm]
> > [<ffffffffa00a6ccd>] drm_atomic_helper_plane_set_property+0x8d/0xd0 [drm_kms_helper]
> > [<ffffffffa00f1fed>] drm_mode_plane_set_obj_prop+0x2d/0x90 [drm]
> > [<ffffffffa00a8a1b>] restore_fbdev_mode+0x6b/0xf0 [drm_kms_helper]
> > [<ffffffffa00aa969>] drm_fb_helper_restore_fbdev_mode_unlocked+0x29/0x80 [drm_kms_helper]
> > [<ffffffffa00aa9e2>] drm_fb_helper_set_par+0x22/0x50 [drm_kms_helper]
> > [<ffffffffa050a71a>] intel_fbdev_set_par+0x1a/0x60 [i915]
> > [<ffffffff813ad444>] fbcon_init+0x4f4/0x580
> >
> > That's because we update the plane state with the fb from the firmware, but we
> > never associate the plane to that CRTC.
> >
> > We don't quite have the full DRM take over from HW state just yet, so
> > fake enough of the plane atomic state to pass the checks.
> >
> > Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_display.c | 9 +++++++--
> > 1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 0d07535..eed1c0c 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -2439,8 +2439,12 @@ intel_find_plane_obj(struct intel_crtc *intel_crtc,
> > return;
> >
> > if (intel_alloc_plane_obj(intel_crtc, plane_config)) {
> > - intel_crtc->base.primary->fb = &plane_config->fb->base;
> > - update_state_fb(intel_crtc->base.primary);
> > + struct drm_plane *primary = intel_crtc->base.primary;
> > +
> > + primary->fb = &plane_config->fb->base;
> > + primary->state->crtc = &intel_crtc->base;
>
> Would
>
> drm_atomic_set_crtc_for_plane(primary->state, &intel_crtc->base)
>
> be better here so that the various bitmasks get updated?

So, this is what I tried first, but it was oopsing in:

0x1fd31 is in drm_atomic_get_crtc_state (drivers/gpu/drm/drm_atomic.c:205).
200 int ret, index;
201 struct drm_crtc_state *crtc_state;
202
203 index = drm_crtc_index(crtc);
204
205 if (state->crtc_states[index])
206 return state->crtc_states[index];
207
208 ret = drm_modeset_lock(&crtc->mutex, state->acquire_ctx);
209 if (ret)

Presumably because we don't have a atomic modeset context setup in
->state when initially reading out the hw state.

I went for the shortest way to make the warnings stop.

>
> > + update_state_fb(primary);
> > +
> > return;
> > }
> >
> > @@ -2469,6 +2473,7 @@ intel_find_plane_obj(struct intel_crtc *intel_crtc,
> >
> > drm_framebuffer_reference(c->primary->fb);
> > intel_crtc->base.primary->fb = c->primary->fb;
> > + c->state->crtc = &intel_crtc->base;
>
> I'm not sure I understand this line. c->state is the crtc state for the
> other CRTC we're going to share with with (and has a backpointer of
> c->state->crtc = c). Was this supposed to be something like
>
> drm_atomic_set_crtc_for_plane(intel_crtc->base.primary->state,
> &intel_crtc->base)
>
> instead? I'm not sure if updating the other crtc (that we're sharing
> with) was a mistake here.

I did mean to write:
intel_crtc->base.primary->state->crtc = &intel_crtc->base;

--
Damien