On Tuesday 11 March 2008 08:08:32 Graeme Gregory wrote: > On Tue, 11 Mar 2008 00:56:03 +0100 > > Stanislav Brabec <[EMAIL PROTECTED]> wrote: > > PXA270 manual talks about 256kiB of RAM directly on the chip. Do > > you know, whether it is used for any purpose just now and whether > > it is faster than external memory? > > According to the manual it is, and they even give a suggestion of its > use. Put the Y and U plane in SRAM and the V plane (because it doesnt > fit) in DRAM. > > Richard Purdie has a patch in linux-rp that allows you to allocate > SRAM, you just need to attach this to the pxa fb stuff. > That only works for 320x240 or so, and I've never seen a performance problem at these resolutions anyway.
I think they were proposing to put the actual base fb in sram too: For YV12 320x240 you need 75kB for Y, and 18.75kB for each of U and V That's only 112.5kB If you had the main frame buffer of 320x240x16 bit that would be 150kB So if you had the base in SRAM, you would not be able to fit the base, Y, U and V, so should put V in SDRAM. The system would probably be much happier like this - the whole problem is the chip isn't really spec-ed to run at 640x480. If it was it would have some more sram, and hardware scaling for the video. > Graeme > > _______________________________________________ > Angstrom-distro-users mailing list > [email protected] > http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/angstrom-distro-u >sers _______________________________________________ Angstrom-distro-users mailing list [email protected] http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/angstrom-distro-users
