Re: [RFC] dmadev: add QoS capability

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Jul 29, 2024 at 03:14:55PM +0200, Morten Brørup wrote:
> > From: Vamsi Attunuru [mailto:vattunuru@marvell.com]
> > Sent: Monday, 29 July 2024 13.56
> > 
> > Some DMA controllers support QoS at HW command queue level to
> > differentiate the performance on different HW queues based on
> > the priority configured. Patch adds required fields in dmadev
> > structures to get hardware supported priority levels and the
> > provision to configure the priority from the applications.
> 
> Do we foresee anything more advanced than Strict Priority scheduling for DMA anytime in the future?
> 
> If not, then consider calling this new capability Prioritization (CAPA_PRIO) instead of Quality Of Service (CAPA_QOS). Then we don't need to add and describe QoS parameters for a more advanced QoS scheduling algorithm (e.g. the "weight" for weighted fair queueing).
> 

There could be more than just regular prioritization settings involved, so
I think it's best to leave some options open. Even with just a
"prioritization" setting, it could be used as a weighting vs strict priority.
Question is whether in such a case - of a single-value number for high vs
low priority - it's better to explicitly separate out a weight priority vs
a strict priority, or give a simpler interface by allowing just a single
number value.

/Bruce