From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Subject: Re: radeon, apertures & memory mapping Date: Mon, 14 Mar 2005 02:39:18 +0200 Message-ID: <20050314003918.GA20886@sci.fi> References: <20050313103936.GA11002@sci.fi> <1110715499.14684.132.camel@gaston> <9e473391050313081937cde207@mail.gmail.com> <1110750553.5787.155.camel@gaston> <9e47339105031314101c89e50e@mail.gmail.com> <1110752401.19810.177.camel@gaston> <9e47339105031315002a444f00@mail.gmail.com> <20050313232735.GA19781@sci.fi> <1110757699.5787.196.camel@gaston> <9e47339105031316254524f72@mail.gmail.com> Reply-To: linux-fbdev-devel@lists.sourceforge.net Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline In-Reply-To: <9e47339105031316254524f72@mail.gmail.com> Sender: linux-fbdev-devel-admin@lists.sourceforge.net Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="iso-8859-1" To: Jon Smirl Cc: Benjamin Herrenschmidt , Jon Smirl , dri-devel@lists.sourceforge.net, Linux Fbdev development list , xorg@lists.freedesktop.org On Sun, Mar 13, 2005 at 07:25:15PM -0500, Jon Smirl wrote: > On Mon, 14 Mar 2005 10:48:19 +1100, Benjamin Herrenschmidt > wrote: > >=20 > > > > That shouldn't matter the page brought in would be for a speculat= ive > > > > read and never accessed. It should just fall out of the cache and= not > > > > be written back. There is only one cachable mapping. In this mode= l > > > > writes are always followed by a flush before telling the GPU to a= ccess > > > > the memory that has just been written. > > > > > > What about this scenario? > > > > > > Speculative read -> AGP master writes new data -> CPU has invalid d= ata in > > > cache :( > >=20 >=20 > You need to reverse the cache flush process if you are going to read > data written by the GPU. >=20 > 1) Make sure GPU is finished writing > 2) flush your cache > 3) read AGP memory like normal RAM. Oh right. The CPU shouldn't write back the cached data since it hasn't=20 changed. I think you'd also need the GPU to issue an AGP flush command between=20 steps 1 and 2. --=20 Ville Syrj=E4l=E4 syrjala@sci.fi http://www.sci.fi/~syrjala/ ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click