Re: [RFC PATCH 09/11] devfreq: exynos-bus: Add interconnect functionality to exynos-bus

[Artur ÅwigoÅ]

Hi,

Thank you for your comments.

On Tue, 2019-08-06 at 13:41 +0000, Leonard Crestez wrote:
> On 23.07.2019 15:21, Artur ÅwigoÅ wrote:
> 
> > +static int exynos_bus_icc_aggregate(struct icc_node *node, u32 avg_bw,
> > +				    u32 peak_bw, u32 *agg_avg, u32 *agg_peak)
> > +{
> > +	*agg_peak = *agg_avg = peak_bw;
> > +
> > +	return 0;
> > +}
> 
> The only current provider aggregates "avg" with "sum" and "peak" with 
> "max", any particular reason to do something different? This function 
> doesn't even really do aggregation, if there is a second request for "0" 
> then the first request is lost.

Yes, you're right. I adopted an oversimplified solution for the purpose of this
RFC (please bear in mind that currently only one icc_path is used, so there is
no aggregation anyway).

> I didn't find any docs but my interpretation of avg/peak is that "avg" 
> is for constant traffic like a display or VPU pushing pixels and "peak" 
> is for variable traffic like networking. I assume devices which make 
> "peak" requests are aggregated with max because they're not expected to 
> all max-out together.

That's correct (according to my understanding).

> In PATCH 11 you're making a bandwidth request based on resolution, that 
> traffic is constant and guaranteed to happend while the display is on so 
> it would make sense to request it as an "avg" and aggregate it with "sum".
> 
> --
> Regards,
> Leonard
> 
-- 
Artur ÅwigoÅ
Samsung R&D Institute Poland
Samsung Electronics