Re: [PATCH 5/5] drm/vblank: Lock down vblank->hwmode more

From: Daniel Vetter <daniel@ffwll.ch>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH 5/5] drm/vblank: Lock down vblank->hwmode more
Date: Thu, 4 May 2017 15:20:22 +0200	[thread overview]
Message-ID: <20170504131930.f47qqrwfbadsciq7@phenom.ffwll.local> (raw)
In-Reply-To: <20170503140908.GL12629@intel.com>

On Wed, May 03, 2017 at 05:09:08PM +0300, Ville Syrjälä wrote:
> On Wed, May 03, 2017 at 09:26:38AM +0200, Daniel Vetter wrote:
> > In the previous patch we've implemented hwmode tracking a la i915 for
> > the vblank timestamp calculations. But that was just the basic
> > semantics, i915 has some nice sanity checks to make sure we keep
> > getting this right. Move them over too.
> > 
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/gpu/drm/drm_irq.c            |  8 +++++++-
> >  drivers/gpu/drm/i915/i915_irq.c      | 10 ++++++----
> >  drivers/gpu/drm/i915/intel_display.c | 11 ++---------
> >  3 files changed, 15 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> > index 89f0928b042a..942183a2aa3c 100644
> > --- a/drivers/gpu/drm/drm_irq.c
> > +++ b/drivers/gpu/drm/drm_irq.c
> > @@ -775,8 +775,10 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
> >  	/* If mode timing undefined, just return as no-op:
> >  	 * Happens during initial modesetting of a crtc.
> >  	 */
> > -	if (mode->crtc_clock == 0) {
> > +	if (WARN_ON(mode->crtc_clock == 0)) {
> >  		DRM_DEBUG("crtc %u: Noop due to uninitialized mode.\n", pipe);
> > +		WARN_ON(drm_drv_uses_atomic_modeset(dev));
> 
> I would make these _ONCE() otherwise the machine might end up
> practically dead.

Will do.

> > +
> >  		return false;
> >  	}
> >  
> > @@ -1338,6 +1340,10 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc)
> >  		send_vblank_event(dev, e, seq, &now);
> >  	}
> >  	spin_unlock_irqrestore(&dev->event_lock, irqflags);
> > +
> > +	/* Will be reset by the modeset helpers when re-enabling the crtc by
> > +	 * calling drm_calc_timestamping_constants(). */
> > +	vblank->hwmode.crtc_clock = 0;
> >  }
> >  EXPORT_SYMBOL(drm_crtc_vblank_off);
> 
> Shouldn't we do this in drm_crtc_vblank_reset() as well?
> 
> Hmm. Except we call that after drm_calc_timestamping_constants(). I
> guess we should be able to move the reset() into
> intel_modeset_readout_hw_state(). And possibly move the vblank_on()
> call as well?

Yeah, it'd be nice to clean this stuff up some more, but there's also the
problem that legacy and new drivers callc drm_calc_timestamping_constants
at opposite ends of the modeset sequence. Doing more here is a bunch more
work, maybe for the next patche series ...

I don't think we need to call it in _reset, at least at boot-up it should
be 0 already. And for s/r we already shut down the pipe on suspend, so
it's gone through this here.

With the _ONCE nit address (and the build breakage I've introduced in this
version fixed), ack from you on the entire series?

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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