Andrea 
I'm testing audio device, using aplay with a pcm uncompressed audio file on sd card. at the first play after linux booting, there is massive sd card access (the virtual file system cache is empty) and sometime audio freeze. I think the problem is the kernel s3c mmc driver compiled in pio mode (not using dma, but polling mode). there is a s3c dma driver but it is experimental, i try it but seems don't work. Anyone can help me ?