Q: dma requires copying into dma buffer - so what's the benefit ?

Hello, There is something I don't understand about dma, when doing memory to memory dma, it requires to cllocate dma buffer (for example with dma_alloc_coherent), than for each transfer we need to copy the buffer to the allocated memory and than trigger dma transaction. So, if it requires additional memcpy for each transaction , what's the benefit of using dma ? without dma: 1. copy buffer (memcpy) from source to destination with dma: 1. copy buffer (memcpy) from source to dma buffer 2. trigger dma transaction (which shall copy the buffer eventually to destination buffer) Regards, Ran