Altera PCI Express Development Kit: Linux DMA Driver

hi all,

i'm trying to write a custom driver based on the altpciechdma example. i saw the following lines of code:

/* soft-reset DMA write engine */

iowrite32(0x0000ffffUL, &write_header->w0);

/* soft-reset DMA read engine */

iowrite32(0x0000ffffUL, &read_header->w0);

my driver works when i perform these actions and it doesn't work if i don't. i'm wondering how you figured this out as i didn't find such a reset command in the documentation of the chaining dma design example.

thanks in advance,

carlos