On 04/15/2014 05:13 PM, Laurent Pinchart wrote:
Fly-by transfer mode cuts down the number of bus transactions by letting
the slave drive or latch the memory data bus during memory transactions
instead of performing a dedicated transaction to read data from or write
data to the slave.
Support for fly-by mode by adding a new flag field to struct
dma_slave_config.
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
include/linux/dmaengine.h | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index c5c92d5..ae99153 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -304,6 +304,17 @@ enum dma_slave_buswidth {
};
/**
+ * enum dma_slave_flags - DMA slave configuration flags
+ * @DMA_SLAVE_FLAG_FLY_BY - perform DMA transfers for the slave in fly-by mode.
+ * Instead of performing a bus transaction to read (write) data from (to) the
+ * slave, let the slave drive (latch) the memory bus data signals during the
+ * memory write (read) transaction.
+ */
Is there any reason not to use fly-by mode for memory to peripheral or
peripheral to memory transfers, if fly-by mode is available? And if not how
should generic drivers using the DMAengine API decide when to use fly-by mode
and when not?
- Lars
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