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.
+ */
+enum dma_slave_flags {
+ DMA_SLAVE_FLAG_FLY_BY = (1 << 0),
+};
+
+/**
* struct dma_slave_config - dma slave channel runtime config
* @direction: whether the data shall go in or out on this slave
* channel, right now. DMA_MEM_TO_DEV and DMA_DEV_TO_MEM are
@@ -333,6 +344,7 @@ enum dma_slave_buswidth {
* @slave_id: Slave requester id. Only valid for slave channels. The dma
* slave peripheral will have unique id as dma requester which need to be
* pass as slave config.
+ * @flags: DMA slave flags, a combination of enum dma_slave_flags flags.
*
* This struct is passed in as configuration data to a DMA engine
* in order to set up a certain channel for DMA transport at runtime.
@@ -361,6 +373,7 @@ struct dma_slave_config {
u32 dst_maxburst;
bool device_fc;
unsigned int slave_id;
+ u32 flags;
};
/**
--
1.8.3.2
--
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