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Date:   Tue, 16 Apr 2019 09:34:20 +0200
From:   Daniel Vetter <daniel@ffwll.ch>
To:     Liviu Dudau <Liviu.Dudau@arm.com>
Cc:     "james qian wang (Arm Technology China)" <james.qian.wang@arm.com>,
        "airlied@linux.ie" <airlied@linux.ie>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "maxime.ripard@bootlin.com" <maxime.ripard@bootlin.com>,
        nd <nd@arm.com>, "sean@poorly.run" <sean@poorly.run>,
        Ben Davis <Ben.Davis@arm.com>
Subject: Re: [v2,1/2] drm: Add writeback_w,h properties
Message-ID: <20190416073419.GN2665@phenom.ffwll.local>
Mail-Followup-To: Liviu Dudau <Liviu.Dudau@arm.com>,
        "james qian wang (Arm Technology China)" <james.qian.wang@arm.com>,
        "airlied@linux.ie" <airlied@linux.ie>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "maxime.ripard@bootlin.com" <maxime.ripard@bootlin.com>,
        nd <nd@arm.com>, "sean@poorly.run" <sean@poorly.run>,
        Ben Davis <Ben.Davis@arm.com>
References: <1555078094-6587-2-git-send-email-ben.davis@arm.com>
 <20190415075922.GA24596@james-ThinkStation-P300>
 <20190415092045.GO15144@e110455-lin.cambridge.arm.com>
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On Mon, Apr 15, 2019 at 10:20:45AM +0100, Liviu Dudau wrote:
> On Mon, Apr 15, 2019 at 08:59:30AM +0100, james qian wang (Arm Technology China) wrote:
> > On Fri, Apr 12, 2019 at 02:08:28PM +0000, Ben Davis wrote:
> > > Add new properties to specify width and height for writeback.
> > > 
> > > Signed-off-by: Ben Davis <ben.davis@arm.com>
> > > ---
> > >  drivers/gpu/drm/drm_atomic_uapi.c |  8 ++++++++
> > >  drivers/gpu/drm/drm_writeback.c   | 28 ++++++++++++++++++++++++++++
> > >  include/drm/drm_connector.h       |  4 ++++
> > >  include/drm/drm_mode_config.h     | 10 ++++++++++
> > >  4 files changed, 50 insertions(+)
> > > 
> > > -- 
> > > 2.7.4
> > > 
> > > diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> > > index d520a04..1f68dce 100644
> > > --- a/drivers/gpu/drm/drm_atomic_uapi.c
> > > +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> > > @@ -765,6 +765,10 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector,
> > >  			return -EINVAL;
> > >  		}
> > >  		state->content_protection = val;
> > > +	} else if (property == config->prop_writeback_w) {
> > > +		state->writeback_w = val;
> > > +	} else if (property == config->prop_writeback_h) {
> > > +		state->writeback_h = val;
> > >  	} else if (property == config->writeback_fb_id_property) {
> > >  		struct drm_framebuffer *fb = drm_framebuffer_lookup(dev, NULL, val);
> > >  		int ret = drm_atomic_set_writeback_fb_for_connector(state, fb);
> > > @@ -837,6 +841,10 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
> > >  		*val = state->scaling_mode;
> > >  	} else if (property == connector->content_protection_property) {
> > >  		*val = state->content_protection;
> > > +	} else if (property == config->prop_writeback_w) {
> > > +		*val = state->writeback_w;
> > > +	} else if (property == config->prop_writeback_h) {
> > > +		*val = state->writeback_h;
> > >  	} else if (property == config->writeback_fb_id_property) {
> > >  		/* Writeback framebuffer is one-shot, write and forget */
> > >  		*val = 0;
> > > diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> > > index c20e6fe..3d0453e 100644
> > > --- a/drivers/gpu/drm/drm_writeback.c
> > > +++ b/drivers/gpu/drm/drm_writeback.c
> > > @@ -74,6 +74,12 @@
> > >   *	applications making use of writeback connectors *always* retrieve an
> > >   *	out-fence for the commit and use it appropriately.
> > >   *	From userspace, this property will always read as zero.
> > > + *
> > > + *  "WRITEBACK_W":
> > > + *	The width of the writeback buffer to write back. 0 acts as default.
> > > + *
> > > + *  "WRITEBACK_H":
> > > + *	The height of the writeback buffer to write back. 0 acts as default.
> > >   */
> > >  
> > >  #define fence_to_wb_connector(x) container_of(x->lock, \
> > > @@ -141,6 +147,22 @@ static int create_writeback_properties(struct drm_device *dev)
> > >  		dev->mode_config.writeback_out_fence_ptr_property = prop;
> > >  	}
> > >  
> > > +	if (!dev->mode_config.prop_writeback_w) {
> > > +		prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
> > > +						 "WRITEBACK_W", 1, UINT_MAX);
> > > +		if (!prop)
> > > +			return -ENOMEM;
> > > +		dev->mode_config.prop_writeback_w = prop;
> > > +	}
> > > +
> > > +	if (!dev->mode_config.prop_writeback_h) {
> > > +		prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
> > > +						 "WRITEBACK_H", 1, UINT_MAX);
> > > +		if (!prop)
> > > +			return -ENOMEM;
> > > +		dev->mode_config.prop_writeback_h = prop;
> > > +	}
> > > +
> > >  	return 0;
> > >  }
> > >  
> > > @@ -225,6 +247,12 @@ int drm_writeback_connector_init(struct drm_device *dev,
> > >  	drm_object_attach_property(&connector->base,
> > >  				   config->writeback_pixel_formats_property,
> > >  				   blob->base.id);
> > > +
> > > +	drm_object_attach_property(&connector->base,
> > > +				   config->prop_writeback_w, 0);
> > > +	drm_object_attach_property(&connector->base,
> > > +				   config->prop_writeback_h, 0);
> > 
> > Hi Ben:
> > Do we real need these two individual properties for specifing the writeback
> > w/h, can we use fb->w/h ?
> > And since these two properties are added as common and standard properties,
> > it influnce all existing write-back implementation which all assumed
> > writeback size as fb->w/h.
> 
> The idea of having these additional properties was to maintain backwards
> compatibility (of some sort). If you don't set writeback_w/h then the
> assumption is that they are the same as fb->w/h, but I can see how it's
> going to be confusing to have fb->w/h different from crtc->w/h and
> different from writeback_w/h.

Since we already have crtc_w/h independent of writeback_fb_w/h, do we need
another set of w/h? Are all the interactions between these tree
well-defined?

Atm I'm assuming that writeback is using crtc_w/h into the fb, at offset
0, not scaled any further. But the planes themselves can be scaled into
the crtc_w/h window ofc.

Iirc the hw supporting writeback thus far needs a dedicated crtc for
writeback, so adding yet another scaling window is not needed?
-Daniel

> > To compatible with existing writeback support, I suggest to keep to
> > use fb->w/h or add these properties as malidp private.
> 
> We don't need to make them malidp private, there is nothing malidp
> specific in them. I'll talk with Ben, we should probably drop this patch
> entirely and just enable malidp scaling when fb->w/h differ from
> crtc->w/h.
> 
> Best regards,
> Liviu
> 
> 
> > 
> > Thanks
> > James
> > 
> > 
> > >  	wb_connector->pixel_formats_blob_ptr = blob;
> > >  
> > >  	return 0;
> > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > > index 8fe22ab..51c4cb2 100644
> > > --- a/include/drm/drm_connector.h
> > > +++ b/include/drm/drm_connector.h
> > > @@ -515,6 +515,10 @@ struct drm_connector_state {
> > >  	 */
> > >  	struct drm_writeback_job *writeback_job;
> > >  
> > > +	/** @writeback_w: width of plane to write to wb buffer */
> > > +	/** @writeback_h: height of plane to write to wb buffer */
> > > +	uint32_t writeback_w, writeback_h;
> > > +
> > >  	/**
> > >  	 * @max_requested_bpc: Connector property to limit the maximum bit
> > >  	 * depth of the pixels.
> > > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > > index 7f60e8e..a0c2133 100644
> > > --- a/include/drm/drm_mode_config.h
> > > +++ b/include/drm/drm_mode_config.h
> > > @@ -622,6 +622,16 @@ struct drm_mode_config {
> > >  	 */
> > >  	struct drm_property *prop_crtc_h;
> > >  	/**
> > > +	 * @prop_writeback_w: Writeback connector property for the plane
> > > +	 * destination position in the writeback buffer.
> > > +	 */
> > > +	struct drm_property *prop_writeback_w;
> > > +	/**
> > > +	 * @prop_writeback_h: Writeback connector property for the plane
> > > +	 * destination position in the writeback buffer.
> > > +	 */
> > > +	struct drm_property *prop_writeback_h;
> > > +	/**
> > >  	 * @prop_fb_id: Default atomic plane property to specify the
> > >  	 * &drm_framebuffer.
> > >  	 */
> > 
> > Pls del this window style line ending 
> > 
> 
> -- 
> ====================
> | I would like to |
> | fix the world,  |
> | but they're not |
> | giving me the   |
>  \ source code!  /
>   ---------------
>     ¯\_(ツ)_/¯
> _______________________________________________
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> dri-devel@lists.freedesktop.org
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch