[Sound-open-firmware] [PATCH v2 2/3] dai: set dai dma burst_elems according to slot number

[Liam Girdwood]

On Tue, 2017-12-19 at 14:11 +0000, Jie, Yang wrote:
> > > We should set burst_elems for dma peripheral dev copy, for dai/ssp, it
> > > should be set to valid slot number, otherwise, the dma may copy in
> > > wrong burst size and data will run with wrong speed.
> > 
> > I don't think the commit message reflects the code, it's really the total number of
> > active slots and not the slot number(s) that we care about, right?
> 
> This is a good topic. At the moment, we are using topology file to configure dai,
> e.g. DAI_TDM(2, 20, 3, 3), which set num_slots(corresponding to 'slot number(s)'
> you mentioned?) to 2 and tx slot mask to 0x3(slot0and slot1 enabled, corresponding
> to 'the total number' in your context?), so they are same for us actually at this case.
> 
> But imagine that if we set tx slot mask to, e.g. 0x1, should we set burst_elems to
> 1 or 2? I tend to set 1 at this case, but not 100% sure about it yet, Maybe we need
> experiment and fix bugs if exist.
> 
> So back to your question, I think the answer is yes, using active slots number may
> be more accurate, though we need experiment on that later.

Keyon, can you submit a patch that make this obvious by means of a code
comment or variable name change.

Thanks

Liam