Re: [PATCH v3 12/13] drm/i915: Only update mode related state if a modeset happened.

From: Daniel Vetter <daniel@ffwll.ch>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH v3 12/13] drm/i915: Only update mode related state if a modeset happened.
Date: Thu, 6 Aug 2015 18:01:02 +0200	[thread overview]
Message-ID: <20150806160102.GB17734@phenom.ffwll.local> (raw)
In-Reply-To: <55C36A02.3010600@linux.intel.com>

On Thu, Aug 06, 2015 at 04:06:58PM +0200, Maarten Lankhorst wrote:
> Op 06-08-15 om 15:12 schreef Daniel Vetter:
> > On Wed, Aug 05, 2015 at 12:37:10PM +0200, Maarten Lankhorst wrote:
> >> The rest will be a noop anyway, since without modeset there will be
> >> no updated dplls and no modeset state to update.
> >>
> >> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/intel_display.c | 30 +++++++-----------------------
> >>  1 file changed, 7 insertions(+), 23 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> >> index 1fd8b7dec7da..aa444cbc2262 100644
> >> --- a/drivers/gpu/drm/i915/intel_display.c
> >> +++ b/drivers/gpu/drm/i915/intel_display.c
> >> @@ -12181,33 +12181,15 @@ fail:
> >>  	return ret;
> >>  }
> >>  
> >> -static bool intel_crtc_in_use(struct drm_crtc *crtc)
> >> -{
> >> -	struct drm_encoder *encoder;
> >> -	struct drm_device *dev = crtc->dev;
> >> -
> >> -	list_for_each_entry(encoder, &dev->mode_config.encoder_list, head)
> >> -		if (encoder->crtc == crtc)
> >> -			return true;
> >> -
> >> -	return false;
> >> -}
> >> -
> >>  static void
> >> -intel_modeset_update_state(struct drm_atomic_state *state)
> >> +intel_modeset_update_crtc_state(struct drm_atomic_state *state)
> >>  {
> >>  	struct drm_crtc *crtc;
> >>  	struct drm_crtc_state *crtc_state;
> >>  	int i;
> >>  
> >> -	intel_shared_dpll_commit(state);
> > This should be right next to swap_state, and we should probably rename it
> > to be consistent.
> After some digging I think this could work if we no longer check pll->config.crtc_mask
> in intel_disable_shared_dpll.
> 
> If we check crtc_mask in intel_enable_shared_dpll we can remove the one from disable
> and prepare, and let the hw checker deal with it.

Yeah I think moving all the state checks into the checker would be useful
- my comment was really a high-level "this is how it should be" comment,
without looking into the details ;-9

> >> -
> >> -	drm_atomic_helper_update_legacy_modeset_state(state->dev, state);
> > This helper should always work, why try to optimize things?
> I didn't see the point of going through the connector state,
> but shrug I guess the extra loops probably don't matter.

modeset is expensive, a few more loops won't hurt I think.

> >> -
> >>  	/* Double check state. */
> >>  	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> >> -		WARN_ON(crtc->state->enable != intel_crtc_in_use(crtc));
> > I guess this WARN_ON should be moved into the state checker? Or entirely
> > removed if redundant.
> It's removed because the atomic core does this for us.

Separate patch and should be explained in the commit message ;-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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