HI Laurent,
On 03-07-20, 20:47, Laurent Pinchart wrote:
> On Fri, Jul 03, 2020 at 11:07:10PM +0530, Vinod Koul wrote:
> > On 03-07-20, 20:22, Laurent Pinchart wrote:
> > > On Fri, Jul 03, 2020 at 10:40:39PM +0530, Vinod Koul wrote:
> > > > On 28-05-20, 05:52, Laurent Pinchart wrote:
> > > >
> > > > > @@ -176,6 +178,18 @@ struct dma_interleaved_template {
> > > > > * @DMA_PREP_CMD: tell the driver that the data passed to DMA API is command
> > > > > * data and the descriptor should be in different format from normal
> > > > > * data descriptors.
> > > > > + * @DMA_PREP_REPEAT: tell the driver that the transaction shall be automatically
> > > > > + * repeated when it ends if no other transaction has been issued on the same
> > > > > + * channel. If other transactions have been issued, this transaction completes
> > > > > + * normally. This flag is only applicable to interleaved transactions and is
> > > > > + * ignored for all other transaction types.
> > > >
> > > > 1. Let us not restrict this to only interleave (hint we can in future
> > > > replace cyclic API)
> > >
> > > Peter wanted to already implement support for DMA_PREP_REPEAT in other
> > > transaction types, and you replied that you would prefer not enabling
> > > APIs without users, waiting for the first user of DMA_PREP_REPEAT with a
> > > non-interleaved transaction to do so. Your comment here seems to
> > > contract that. Which way do you want to go ?
> >
> > I would like to change the language of the explanation to not forbid
> > other uses, but they would be enabled in txn when we have users..
>
> The documentation isn't set in stone, it can be updated when support for
> DMA_PREP_REPEAT will be enabled in other transaction types. I think it's
> better to have the documentation and code match, the documentation
> should describe the current implementation. I can add an additional
> sentence at the end of the paragraph to state "Support for this flag in
> other transaction types may be added in the future if the need arises."
> if that makes you feel better about it.
Okay I will be okay with that caveat
> > > > 2. DMA_PREP_REPEAT telling the transaction shall be automatically
> > > > repeated is okay. No issues with that
> > > >
> > > > > + * @DMA_PREP_LOAD_EOT: tell the driver that the transaction shall replaced any
> > > >
> > > > s/replaced/replace
> > > >
> > > > > + * active repeated (as indicated by DMA_PREP_REPEAT) transaction when the
> > > > > + * repeated transaction terminate. Not setting this flag when the previously
> > > > > + * queued transaction is marked with DMA_PREP_REPEAT will cause the new
> > > > > + * transaction to never be processed and stay in the issued queue forever.
> > > > > + * The flag is ignored if the previous transaction is not a repeated
> > > > > + * transaction.
> > > >
> > > > I am happy with this bit, I think we dont need to specify something like
> > > > DMA_PREP_LOAD_NEXT given the explanation here, so adding
> > > > DMA_PREP_LOAD_EOT would mean that.
> > >
> > > Just to clarify, does that mean I don't need to add a DMA_PREP_LOAD_NEXT
> > > flag in the API ?
> > >
> > > > Can we add a corresponding EOB as well to complete this
> > >
> > > What's EOB ?
> >
> > End of Burst, DMA would complete current burst and then terminate. I do
> > understand it is not applicable for your case as your hw doesn't support
> > it and would be unused but this is another case which would be useful so
> > for completeness we should add this
>
> Why not add it when we'll have a user for it ? How can you otherwise
> guarantee that it's a correct API if there's not even a single user that
> we can test the design with ?
Okay lets not add but add a note that additional flags can be added when
required like EOB
Also can we add a note in Documentation about these flags and how they
should be used for repeating transactions.
Thanks
--
~Vinod
