| Message ID | 1397574817-15559-2-git-send-email-laurent.pinchart@ideasonboard.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Apr 15, 2014 at 05:13:32PM +0200, 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@ideasonboard.com> > --- > 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; > }; I am not sure about this. Should we have a generic flag for this or just add a bool for fly_by mode? Suggestions?
On Fri, May 02, 2014 at 09:16:34PM +0530, Vinod Koul wrote: + Dan Pls cc Dan as well ~Vinod > On Tue, Apr 15, 2014 at 05:13:32PM +0200, 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@ideasonboard.com> > > --- > > 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; > > }; > I am not sure about this. Should we have a generic flag for this or just add a > bool for fly_by mode? > > Suggestions? > > -- > ~Vinod >
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@ideasonboard.com> > --- > 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
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; }; /**
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@ideasonboard.com> --- include/linux/dmaengine.h | 13 +++++++++++++ 1 file changed, 13 insertions(+)