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From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Eric Anholt <eric@anholt.net>
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v2 3/3] drm/vc4: Add a load tracker to prevent HVS underflow errors
Date: Tue, 6 Nov 2018 14:07:13 +0100	[thread overview]
Message-ID: <20181106140713.622fdd2d@bbrezillon> (raw)
In-Reply-To: <87bm7bm3k8.fsf@anholt.net>

On Tue, 30 Oct 2018 16:12:55 -0700
Eric Anholt <eric@anholt.net> wrote:

> > +		/* Even if the bandwidth/plane required for a single frame is
> > +		 *
> > +		 * vc4_state->src_w[i] * vc4_state->src_h[i] * cpp * vrefresh
> > +		 *
> > +		 * when downscaling, we have to read more pixels per line in
> > +		 * the time frame reserved for a single line, so the bandwidth
> > +		 * demand can be punctually higher. To account for that, we
> > +		 * calculate the down-scaling factor and multiply the plane
> > +		 * load by this number. We're likely over-estimating the read
> > +		 * demand, but that's better than under-estimating it.
> > +		 */

One more thing: because we sometimes over estimate the load, we might
reject configuration that were previously accepted, so I'm wondering if
we shouldn't make the 'reject on HVS/membus load too high' optional,
and disable it by default.
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  parent reply	other threads:[~2018-11-06 13:07 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-25 12:45 [PATCH v2 0/3] drm/vc4: Add a load tracker Boris Brezillon
2018-10-25 12:45 ` [PATCH v2 1/3] drm/atomic: Add a generic infrastructure to track underrun errors Boris Brezillon
2018-10-26 10:33   ` Daniel Vetter
2018-10-26 12:36     ` Boris Brezillon
2018-10-26 13:36       ` Daniel Vetter
2018-10-26 14:13         ` Boris Brezillon
2018-10-26 14:23           ` Daniel Vetter
2018-10-25 12:45 ` [PATCH v2 2/3] drm/vc4: Report " Boris Brezillon
2018-10-25 12:45 ` [PATCH v2 3/3] drm/vc4: Add a load tracker to prevent HVS underflow errors Boris Brezillon
2018-10-30 23:12   ` Eric Anholt
2018-11-05 11:36     ` Boris Brezillon
2018-11-08 16:26       ` Eric Anholt
2018-11-08 16:50         ` Boris Brezillon
2018-11-08 17:53           ` Eric Anholt
2018-11-06 13:07     ` Boris Brezillon [this message]
2018-11-28  9:16 ` [PATCH v2 0/3] drm/vc4: Add a load tracker Paul Kocialkowski
2018-11-28  9:29   ` Boris Brezillon
2018-11-28 13:32     ` Paul Kocialkowski

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