linux-kernel - Re: [RFC PATCH 0/3] staging: remove fbdev drivers

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Date:   Tue, 13 Dec 2016 08:33:24 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Dave Airlie <airlied@...il.com>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Teddy Wang <teddy.wang@...iconmotion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Arnaud Patard <arnaud.patard@...-net.org>
Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers

  Hi,

> The acceleration that most of the 2D things provide isn't ever that
> great, and shadowing is a lot more effective if done properly.

That is probably true for anything pci-ish, because those devices are
optimized for memory writes and reads are horribly slow.  So you surely
want avoid device memory reads and shadowing is a effective way to do
this.

On arm hardware the tradeoff may look quite different, the cpus are
relatively slow and I think most arm gpus don't have dedicated device
memory ...

cheers,
  Gerd