Q: dma requires copying into dma buffer - so what's the benefit ?
From: Ruben Safir <hidden>
Date: 2016-09-06 16:54:56
On 09/06/2016 12:24 PM, Ran Shalit wrote:
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)
DMA hardware uses an expedited bus that frees the main memory to be addressed for other processes.
Regards, Ran _______________________________________________ Kernelnewbies mailing list Kernelnewbies at kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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