Re: MPC52xx generic DMA using bestcomm
From: Jon Smirl <hidden>
Date: 2008-07-07 13:39:45
On 7/7/08, Matt Sealey [off-list ref] wrote:
Andre Schwarz wrote:quoted
Grant,I know I'm not Grant, but..quoted
do you know if someone's working on a more generic DMA solution using BestComm engine on 5200B ? Maybe somthing that accepts a sg-list with callback ops or completion ?It was suggested once or twice, not least by me.quoted
Is it possible right now to accelerate simple memcpy ops ?From my discussions on the subject with Sylvain, it's possible, you just need to use the GenBD and initiate it manually, however it's probably more overhead than work if the data size is small, and BestComm would do better to copy full 32-bit words at a time, and stay aligned, if you have an odd-sized transfer from a non-32-bit aligned address, then you may have to do some incredible amount of work which makes the actual transfer not worth doing (by the time you set it up, the CPU could have copied it on it's own already, I guess what you DO gain is a kernel preemption point.. the CPU can do other things that are important)
If you want an Efika specific problem, the audio hardware is capable of simultaneously playing music on the S/PDIF and analog outputs. But to do that the samples have to be alternated as they are fed into the AC97 stream. I think the codec can capture that way too but you didn't put a transceiver on the S/PDIF line. In my test driver you only get AC97 or S/PDIF. Grant and I are both working on i2s drivers, when we get those sorted out it shouldn't be too hard to add ac97 back in. That codec driver I sent you was about 95% complete.
I for one, though, whether it speeds stuff up or not, love to see this in action and am very willing to test and benchmark it. I would love to see more users, too, as the network stack is not the only system that can benefit.. On a related note does anyone know of the status or what is going on with Clifford Wolf's dmatransfer API? -- Matt Sealey [off-list ref] Genesi, Manager, Developer Relations _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
-- Jon Smirl jonsmirl@gmail.com