Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> writes: > Immediate data transfers (IDT) allow the HCD to copy small chunks of > data (up to 8bytes) directly into its output transfer TRBs. This avoids > the somewhat expensive DMA mappings that are performed by default on > most URBs submissions. > > In the case an URB was suitable for IDT. The data is directly copied > into the "Data Buffer Pointer" region of the TRB and the IDT flag is > set. Instead of triggering memory accesses the HC will use the data > directly. > > The implementation could cover all kind of output endpoints. Yet > Isochronous endpoints are bypassed as I was unable to find one that > matched IDT's constraints. As we try to bypass the default DMA mappings > on URB buffers we'd need to find a Isochronous device with an > urb->transfer_buffer_length <= 8 bytes. > > The implementation takes into account that the 8 byte buffers provided > by the URB will never cross a 64KB boundary. > > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> This looks good to my eyes. Reviewed-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx> -- balbi
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