Viresh Kumar <viresh.ku...@linaro.org> writes: > On 21-11-16, 09:07, Rob Herring wrote: >> On Fri, Nov 18, 2016 at 02:53:12PM +0530, Viresh Kumar wrote: >> > Some platforms have the capability to configure the performance state of >> > their Power Domains. The performance levels are represented by positive >> > integer values, a lower value represents lower performance state. >> > >> > The power-domains until now were only concentrating on the idle state >> > management of the device and this needs to change in order to reuse the >> > infrastructure of power domains for active state management. >> > >> > This patch introduces a new optional property for the consumers of the >> > power-domains: domain-performance-state. >> > >> > If the consumers don't need the capability of switching to different >> > domain performance states at runtime, then they can simply define their >> > required domain performance state in their node directly. Otherwise the >> > consumers can define their requirements with help of other >> > infrastructure, for example the OPP table. >> > >> > Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org> >> > --- >> > Documentation/devicetree/bindings/power/power_domain.txt | 6 ++++++ >> > 1 file changed, 6 insertions(+) >> > >> > diff --git a/Documentation/devicetree/bindings/power/power_domain.txt >> > b/Documentation/devicetree/bindings/power/power_domain.txt >> > index e1650364b296..db42eacf8b5c 100644 >> > --- a/Documentation/devicetree/bindings/power/power_domain.txt >> > +++ b/Documentation/devicetree/bindings/power/power_domain.txt >> > @@ -106,6 +106,12 @@ domain provided by the 'parent' power controller. >> > - power-domains : A phandle and PM domain specifier as defined by >> > bindings of >> > the power controller specified by phandle. >> > >> > +Optional properties: >> > +- domain-performance-state: A positive integer value representing the >> > minimum >> > + performance level (of the parent domain) required by the consumer for >> > its >> > + working. The integer value '1' represents the lowest performance level >> > and the >> > + highest value represents the highest performance level. >> >> How does one come up with the range of values? > > Why would we need a range here? The value here represents the minimum 'state' > and the assumption is that everything above that level would be fine. So the > range is automatically: domain-performance-state -> MAX. > >> It seems like you are >> just making up numbers. Couldn't the domain performance level be an OPP >> in the sense that it is a collection of clock frequencies and voltage >> settings? > > The clock is going to be handled by the device itself (at least for the case > we > have today) and the performance-state lies with the power-domain which is > configured separately. If the performance level includes both clk and voltage, > then why would we need to show the clock rates in the DT ? Wouldn't a > performance level be enough in such cases?
I think the question is: what does the performance-level of a domain actually mean? Or, what are the units? Depending on the SoC, there's probably a few things this could mean. It might mean is that an underlying bus/interconnect can be configured to guarantee a specific bandwidth or throughput. That in turn might mean that that bus/interconnect might have to be set at a specific frequency/voltage. In your case, IIUC, you're just passing some magic value to some firmware running on a micro-controller, but under the hood that uC is probably configuring a frequency/voltage someplace. So, if we're going to have a generic DT binding for this, it needs to be something that's useful on platforms that are not using magic numbers managed by a uC as well. Kevin
