On 23 November 2016 at 16:51, Kevin Hilman <khilman@xxxxxxxxxxxx> wrote: > Vincent Guittot <vincent.guittot@xxxxxxxxxx> writes: > >> On 22 November 2016 at 19:12, Kevin Hilman <khilman@xxxxxxxxxxxx> wrote: >>> Viresh Kumar <viresh.kumar@xxxxxxxxxx> 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.kumar@xxxxxxxxxx> >>>>> > --- >>>>> > 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. >> >> In the case described by Viresh, it's only about setting the voltage >> of a power domain that is shared between different devices. these >> devices wants to run at different frequency (set by the devices) but >> we have to select a Volateg value that will match with the constraint >> of all devices (in this case the highest voltage) > > Then, at least for this use case, we're talking about voltage, not some > unspecified units. > > But that makes me wonder, this performance state sounds like something > that is changing dynamically at runtime, so why do you want to describe > this statically in DT? > > This sounds to me like the job of the genpd. When any device in the > domain does its pm_runtime_get(), the domain could check the device > frequency and see if it needs to change the domain voltage in order for > that device to operate at that frequency. When the device goes away > (using pm_runtime_put()) the domain can check again if it could lower > the voltage and still meet the requirements of the remaining devices. That's only part of the job. The device can change its frequency and as a result ask for a new voltage index while it is already running Vincent > > Kevin > > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
