Date:   Mon, 13 May 2019 16:47:47 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Sean Paul <sean@...rly.run>, dri-devel@...ts.freedesktop.org,
        Sean Paul <seanpaul@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Eric Anholt <eric@...olt.net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v3 04/10] drm: Convert
 connector_helper_funcs->atomic_check to accept drm_atomic_state

On Sat, May 11, 2019 at 10:12:02PM +0300, Laurent Pinchart wrote:
> Hi Sean,
> 
> Thank you for the patch.
> 
> On Thu, May 02, 2019 at 03:49:46PM -0400, Sean Paul wrote:
> > From: Sean Paul <seanpaul@...omium.org>
> > 
> > Everyone who implements connector_helper_funcs->atomic_check reaches
> > into the connector state to get the atomic state. Instead of continuing
> > this pattern, change the callback signature to just give atomic state
> > and let the driver determine what it does and does not need from it.
> > 
> > Eventually all atomic functions should do this, but that's just too much
> > busy work for me.
> 
> Given that drivers also access the connector state, isn't this slightly
> more inefficient ?

It's atomic code, we're trying to optimize for clean code at the expense
of a bit of runtime overhead due to more pointer chasing. And I agree with
the general push, the pile of old/new_state pointers of various objects
we're passing around is confusing. Passing the overall drm_atomic_state
seems much more reasonable, and with that we can get everything else. Plus
it's much more obvious whether you have the old/new state (since that's
explicit when you look it up from the drm_atomic_state).

If we ever see this show up in profile, and it starts mattering, first
thing we need is a hashtable I think (atm it's list walking, which is just
terrible). But thus far no one cares.
-Daniel

> 
> > Changes in v3:
> > - Added to the set
> > 
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> > Cc: Jani Nikula <jani.nikula@...ux.intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@...el.com>
> > Cc: Ben Skeggs <bskeggs@...hat.com>
> > Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > Cc: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> > Cc: Eric Anholt <eric@...olt.net>
> > Signed-off-by: Sean Paul <seanpaul@...omium.org>
> > ---
> >  drivers/gpu/drm/drm_atomic_helper.c      |  4 ++--
> >  drivers/gpu/drm/i915/intel_atomic.c      |  8 +++++---
> >  drivers/gpu/drm/i915/intel_dp_mst.c      |  7 ++++---
> >  drivers/gpu/drm/i915/intel_drv.h         |  2 +-
> >  drivers/gpu/drm/i915/intel_sdvo.c        |  9 +++++----
> >  drivers/gpu/drm/i915/intel_tv.c          |  8 +++++---
> >  drivers/gpu/drm/nouveau/dispnv50/disp.c  |  5 +++--
> >  drivers/gpu/drm/rcar-du/rcar_lvds.c      | 12 +++++++-----
> >  drivers/gpu/drm/vc4/vc4_txp.c            |  7 ++++---
> >  include/drm/drm_modeset_helper_vtables.h |  2 +-
> >  10 files changed, 37 insertions(+), 27 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 9d9e47276839..fa5a367507c1 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -683,7 +683,7 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
> >  		}
> >  
> >  		if (funcs->atomic_check)
> > -			ret = funcs->atomic_check(connector, new_connector_state);
> > +			ret = funcs->atomic_check(connector, state);
> >  		if (ret)
> >  			return ret;
> >  
> > @@ -725,7 +725,7 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
> >  			continue;
> >  
> >  		if (funcs->atomic_check)
> > -			ret = funcs->atomic_check(connector, new_connector_state);
> > +			ret = funcs->atomic_check(connector, state);
> >  		if (ret)
> >  			return ret;
> >  	}
> > diff --git a/drivers/gpu/drm/i915/intel_atomic.c b/drivers/gpu/drm/i915/intel_atomic.c
> > index b844e8840c6f..e8a5b82e9242 100644
> > --- a/drivers/gpu/drm/i915/intel_atomic.c
> > +++ b/drivers/gpu/drm/i915/intel_atomic.c
> > @@ -103,12 +103,14 @@ int intel_digital_connector_atomic_set_property(struct drm_connector *connector,
> >  }
> >  
> >  int intel_digital_connector_atomic_check(struct drm_connector *conn,
> > -					 struct drm_connector_state *new_state)
> > +					 struct drm_atomic_state *state)
> >  {
> > +	struct drm_connector_state *new_state =
> > +		drm_atomic_get_new_connector_state(state, conn);
> >  	struct intel_digital_connector_state *new_conn_state =
> >  		to_intel_digital_connector_state(new_state);
> >  	struct drm_connector_state *old_state =
> > -		drm_atomic_get_old_connector_state(new_state->state, conn);
> > +		drm_atomic_get_old_connector_state(state, conn);
> >  	struct intel_digital_connector_state *old_conn_state =
> >  		to_intel_digital_connector_state(old_state);
> >  	struct drm_crtc_state *crtc_state;
> > @@ -118,7 +120,7 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
> >  	if (!new_state->crtc)
> >  		return 0;
> >  
> > -	crtc_state = drm_atomic_get_new_crtc_state(new_state->state, new_state->crtc);
> > +	crtc_state = drm_atomic_get_new_crtc_state(state, new_state->crtc);
> >  
> >  	/*
> >  	 * These properties are handled by fastset, and might not end
> > diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> > index 19d81cef2ab6..89cfec128ba0 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> > @@ -143,9 +143,10 @@ static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
> >  
> >  static int
> >  intel_dp_mst_atomic_check(struct drm_connector *connector,
> > -			  struct drm_connector_state *new_conn_state)
> > +			  struct drm_atomic_state *state)
> >  {
> > -	struct drm_atomic_state *state = new_conn_state->state;
> > +	struct drm_connector_state *new_conn_state =
> > +		drm_atomic_get_new_connector_state(state, connector);
> >  	struct drm_connector_state *old_conn_state =
> >  		drm_atomic_get_old_connector_state(state, connector);
> >  	struct intel_connector *intel_connector =
> > @@ -155,7 +156,7 @@ intel_dp_mst_atomic_check(struct drm_connector *connector,
> >  	struct drm_dp_mst_topology_mgr *mgr;
> >  	int ret;
> >  
> > -	ret = intel_digital_connector_atomic_check(connector, new_conn_state);
> > +	ret = intel_digital_connector_atomic_check(connector, state);
> >  	if (ret)
> >  		return ret;
> >  
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index f8c7b291fdc3..88571b8e8d62 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -2481,7 +2481,7 @@ int intel_digital_connector_atomic_set_property(struct drm_connector *connector,
> >  						struct drm_property *property,
> >  						u64 val);
> >  int intel_digital_connector_atomic_check(struct drm_connector *conn,
> > -					 struct drm_connector_state *new_state);
> > +					 struct drm_atomic_state *state);
> >  struct drm_connector_state *
> >  intel_digital_connector_duplicate_state(struct drm_connector *connector);
> >  
> > diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
> > index 68f497493d43..72ea164b971c 100644
> > --- a/drivers/gpu/drm/i915/intel_sdvo.c
> > +++ b/drivers/gpu/drm/i915/intel_sdvo.c
> > @@ -2342,9 +2342,10 @@ static const struct drm_connector_funcs intel_sdvo_connector_funcs = {
> >  };
> >  
> >  static int intel_sdvo_atomic_check(struct drm_connector *conn,
> > -				   struct drm_connector_state *new_conn_state)
> > +				   struct drm_atomic_state *state)
> >  {
> > -	struct drm_atomic_state *state = new_conn_state->state;
> > +	struct drm_connector_state *new_conn_state =
> > +		drm_atomic_get_new_connector_state(state, conn);
> >  	struct drm_connector_state *old_conn_state =
> >  		drm_atomic_get_old_connector_state(state, conn);
> >  	struct intel_sdvo_connector_state *old_state =
> > @@ -2356,13 +2357,13 @@ static int intel_sdvo_atomic_check(struct drm_connector *conn,
> >  	    (memcmp(&old_state->tv, &new_state->tv, sizeof(old_state->tv)) ||
> >  	     memcmp(&old_conn_state->tv, &new_conn_state->tv, sizeof(old_conn_state->tv)))) {
> >  		struct drm_crtc_state *crtc_state =
> > -			drm_atomic_get_new_crtc_state(new_conn_state->state,
> > +			drm_atomic_get_new_crtc_state(state,
> >  						      new_conn_state->crtc);
> >  
> >  		crtc_state->connectors_changed = true;
> >  	}
> >  
> > -	return intel_digital_connector_atomic_check(conn, new_conn_state);
> > +	return intel_digital_connector_atomic_check(conn, state);
> >  }
> >  
> >  static const struct drm_connector_helper_funcs intel_sdvo_connector_helper_funcs = {
> > diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
> > index 3924c4944e1f..a41c5b467c14 100644
> > --- a/drivers/gpu/drm/i915/intel_tv.c
> > +++ b/drivers/gpu/drm/i915/intel_tv.c
> > @@ -1817,16 +1817,18 @@ static const struct drm_connector_funcs intel_tv_connector_funcs = {
> >  };
> >  
> >  static int intel_tv_atomic_check(struct drm_connector *connector,
> > -				 struct drm_connector_state *new_state)
> > +				 struct drm_atomic_state *state)
> >  {
> > +	struct drm_connector_state *new_state;
> >  	struct drm_crtc_state *new_crtc_state;
> >  	struct drm_connector_state *old_state;
> >  
> > +	new_state = drm_atomic_get_new_connector_state(state, connector);
> >  	if (!new_state->crtc)
> >  		return 0;
> >  
> > -	old_state = drm_atomic_get_old_connector_state(new_state->state, connector);
> > -	new_crtc_state = drm_atomic_get_new_crtc_state(new_state->state, new_state->crtc);
> > +	old_state = drm_atomic_get_old_connector_state(state, connector);
> > +	new_crtc_state = drm_atomic_get_new_crtc_state(state, new_state->crtc);
> >  
> >  	if (old_state->tv.mode != new_state->tv.mode ||
> >  	    old_state->tv.margins.left != new_state->tv.margins.left ||
> > diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> > index 4b1650f51955..7ba373f493b2 100644
> > --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> > +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> > @@ -948,11 +948,12 @@ nv50_mstc_get_modes(struct drm_connector *connector)
> >  
> >  static int
> >  nv50_mstc_atomic_check(struct drm_connector *connector,
> > -		       struct drm_connector_state *new_conn_state)
> > +		       struct drm_atomic_state *state)
> >  {
> > -	struct drm_atomic_state *state = new_conn_state->state;
> >  	struct nv50_mstc *mstc = nv50_mstc(connector);
> >  	struct drm_dp_mst_topology_mgr *mgr = &mstc->mstm->mgr;
> > +	struct drm_connector_state *new_conn_state =
> > +		drm_atomic_get_new_connector_state(state, connector);
> >  	struct drm_connector_state *old_conn_state =
> >  		drm_atomic_get_old_connector_state(state, connector);
> >  	struct drm_crtc_state *crtc_state;
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > index 620b51aab291..5b81ba2a7f27 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > @@ -92,13 +92,15 @@ static int rcar_lvds_connector_get_modes(struct drm_connector *connector)
> >  }
> >  
> >  static int rcar_lvds_connector_atomic_check(struct drm_connector *connector,
> > -					    struct drm_connector_state *state)
> > +					    struct drm_atomic_state *state)
> >  {
> >  	struct rcar_lvds *lvds = connector_to_rcar_lvds(connector);
> >  	const struct drm_display_mode *panel_mode;
> > +	struct drm_connector_state *conn_state;
> >  	struct drm_crtc_state *crtc_state;
> >  
> > -	if (!state->crtc)
> > +	conn_state = drm_atomic_get_new_connector_state(state, connector);
> > +	if (!conn_state->crtc)
> >  		return 0;
> >  
> >  	if (list_empty(&connector->modes)) {
> > @@ -110,9 +112,9 @@ static int rcar_lvds_connector_atomic_check(struct drm_connector *connector,
> >  				      struct drm_display_mode, head);
> >  
> >  	/* We're not allowed to modify the resolution. */
> > -	crtc_state = drm_atomic_get_crtc_state(state->state, state->crtc);
> > -	if (IS_ERR(crtc_state))
> > -		return PTR_ERR(crtc_state);
> > +	crtc_state = drm_atomic_get_crtc_state(state, conn_state->crtc);
> > +	if (!crtc_state)
> > +		return -EINVAL;
> >  
> >  	if (crtc_state->mode.hdisplay != panel_mode->hdisplay ||
> >  	    crtc_state->mode.vdisplay != panel_mode->vdisplay)
> > diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
> > index c8b89a78f9f4..96f91c1b4b6e 100644
> > --- a/drivers/gpu/drm/vc4/vc4_txp.c
> > +++ b/drivers/gpu/drm/vc4/vc4_txp.c
> > @@ -221,17 +221,18 @@ static const u32 txp_fmts[] = {
> >  };
> >  
> >  static int vc4_txp_connector_atomic_check(struct drm_connector *conn,
> > -					struct drm_connector_state *conn_state)
> > +					  struct drm_atomic_state *state)
> >  {
> > +	struct drm_connector_state *conn_state;
> >  	struct drm_crtc_state *crtc_state;
> >  	struct drm_framebuffer *fb;
> >  	int i;
> >  
> > +	conn_state = drm_atomic_get_new_connector_state(state, conn);
> >  	if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
> >  		return 0;
> >  
> > -	crtc_state = drm_atomic_get_new_crtc_state(conn_state->state,
> > -						   conn_state->crtc);
> > +	crtc_state = drm_atomic_get_new_crtc_state(state, conn_state->crtc);
> >  
> >  	fb = conn_state->writeback_job->fb;
> >  	if (fb->width != crtc_state->mode.hdisplay ||
> > diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> > index de57fb40cb6e..adc8b7cf64b5 100644
> > --- a/include/drm/drm_modeset_helper_vtables.h
> > +++ b/include/drm/drm_modeset_helper_vtables.h
> > @@ -1020,7 +1020,7 @@ struct drm_connector_helper_funcs {
> >  	 * deadlock.
> >  	 */
> >  	int (*atomic_check)(struct drm_connector *connector,
> > -			    struct drm_connector_state *state);
> > +			    struct drm_atomic_state *state);
> >  
> >  	/**
> >  	 * @atomic_commit:
> 
> -- 
> Regards,
> 
> Laurent Pinchart

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

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