On 23-01-20, 10:03, Peter Ujfalusi wrote:
> Hi Laurent,
>
> On 23/01/2020 4.29, Laurent Pinchart wrote:
> > The new interleaved cyclic transaction type combines interleaved and
> > cycle transactions. It is designed for DMA engines that back display
> > controllers, where the same 2D frame needs to be output to the display
> > until a new frame is available.
> >
> > Suggested-by: Vinod Koul <vkoul@xxxxxxxxxx>
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > ---
> > drivers/dma/dmaengine.c | 8 +++++++-
> > include/linux/dmaengine.h | 18 ++++++++++++++++++
> > 2 files changed, 25 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> > index 03ac4b96117c..4ffb98a47f31 100644
> > --- a/drivers/dma/dmaengine.c
> > +++ b/drivers/dma/dmaengine.c
> > @@ -981,7 +981,13 @@ int dma_async_device_register(struct dma_device *device)
> > "DMA_INTERLEAVE");
> > return -EIO;
> > }
> > -
> > + if (dma_has_cap(DMA_INTERLEAVE_CYCLIC, device->cap_mask) &&
> > + !device->device_prep_interleaved_cyclic) {
> > + dev_err(device->dev,
> > + "Device claims capability %s, but op is not defined\n",
> > + "DMA_INTERLEAVE_CYCLIC");
> > + return -EIO;
> > + }
> >
> > if (!device->device_tx_status) {
> > dev_err(device->dev, "Device tx_status is not defined\n");
> > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> > index 8fcdee1c0cf9..e9af3bf835cb 100644
> > --- a/include/linux/dmaengine.h
> > +++ b/include/linux/dmaengine.h
> > @@ -61,6 +61,7 @@ enum dma_transaction_type {
> > DMA_SLAVE,
> > DMA_CYCLIC,
> > DMA_INTERLEAVE,
> > + DMA_INTERLEAVE_CYCLIC,
> > /* last transaction type for creation of the capabilities mask */
> > DMA_TX_TYPE_END,
> > };
> > @@ -701,6 +702,10 @@ struct dma_filter {
> > * The function takes a buffer of size buf_len. The callback function will
> > * be called after period_len bytes have been transferred.
> > * @device_prep_interleaved_dma: Transfer expression in a generic way.
> > + * @device_prep_interleaved_cyclic: prepares an interleaved cyclic transfer.
> > + * This is similar to @device_prep_interleaved_dma, but the transfer is
> > + * repeated until a new transfer is issued. This transfer type is meant
> > + * for display.
>
> I think capture (camera) is another potential beneficiary of this.
>
> So you don't need to terminate the running interleaved_cyclic and start
> a new one, but prepare and issue a new one, which would
> terminate/replace the currently running cyclic interleaved DMA?
Why not explicitly terminate the transfer and start when a new one is
issued. That can be common usage for audio and display..
--
~Vinod
