Viresh Kumar viresh.kumar@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.kumar@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