On 7/31/12, Clemens Ladisch <[email protected]> wrote: > Karl Beldan wrote: >> To tx a chunk of data from the SoC => network device, we : >> - prepare a buffer with a leading header embedding a pattern, >> - trigger the xfer and wait for an irq >> // The device updates the pattern and then triggers an irq >> - upon irq we check the pattern for the xfer completion >> >> I was expecting the following to work: >> addr = dma_map_single(dev, buffer, size, DMA_TO_DEVICE); > > Of both the CPU and the device write to the buffer, you must use > DMA_BIDIRECTIONAL. > Hi Clemens,
This does not work (tested) : seems to me BIDIRECTIONAL would just add invalidate, and invalidate before the ram has been updated, as stated, does not work. In fact the immediately following sync_for_device is intended to cater for what DMA_BIDIRECTIONAL would provide (though it is not implementation agnostic), only invalidating a smaller address range. Regards, Karl -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
