Rob Herring <robh@xxxxxxxxxx> writes: > On Wed, Apr 26, 2017 at 04:27:05PM +0530, Viresh Kumar wrote: >> Power-domains need to express their active states in DT and the devices >> within the power-domain need to express their dependency on those active >> states. The power-domains can use the OPP tables without any >> modifications to the bindings. >> >> Add a new property "power-domain-opp", which will contain phandle to the >> OPP node of the parent power domain. This is required for devices which >> have dependency on the configured active state of the power domain for >> their working. >> >> For some platforms the actual frequency and voltages of the power >> domains are managed by the firmware and are so hidden from the high >> level operating system. The "opp-hz" property is relaxed a bit to >> contain indexes instead of actual frequency values to support such >> platforms. >> >> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> >> --- >> Documentation/devicetree/bindings/opp/opp.txt | 74 ++++++++++++++++++++++++++- >> 1 file changed, 73 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt >> index 63725498bd20..6e30cae2a936 100644 >> --- a/Documentation/devicetree/bindings/opp/opp.txt >> +++ b/Documentation/devicetree/bindings/opp/opp.txt >> @@ -77,7 +77,10 @@ This defines voltage-current-frequency combinations along with other related >> properties. >> >> Required properties: >> -- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. >> +- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer. In some >> + cases the exact frequency in Hz may be hidden from the OS by the firmware and >> + this field may contain values that represent the frequency in a firmware >> + dependent way, for example an index of an array in the firmware. > > Not really sure OPP binding makes sense here. I think OPP makes perfect sense here, because microcontroller firmware is managaging OPPs in hardware. We just may not know the exact voltage and/or frequency (and the firmware/hardware may even be doing AVS for micro-adjustments.) > What about all the other properties. We expose voltage, but not freq? I had the same question. Seems the same comment about an abstract "index" is needed for voltage also. >> >> Optional properties: >> - opp-microvolt: voltage in micro Volts. >> @@ -154,6 +157,13 @@ properties. >> >> - status: Marks the node enabled/disabled. >> >> +- power-domain-opp: Phandle to the OPP node of the parent power-domain. The >> + parent power-domain should be configured to the OPP whose node is pointed by >> + the phandle, in order to configure the device for the OPP node that contains >> + this property. The order in which the device and power domain should be >> + configured is implementation defined. The OPP table of a device can set this >> + property only if the device node contains "power-domains" property. >> + I do understand the need to map a device OPP to a parent power-domain OPP, but I really don't like another phandle. First, just because a device OPP changes does not mean that a power-domain OPP has to change. What really needs to be specified is a minimum requirement, not an exact OPP. IOW, if a device changes OPP, the power-domain OPP has to be *at least* an OPP that can guarantee that level of performance, but could also be a more performant OPP, right? Also, the parent power-domain driver will have a list of all its devices, and be able to get OPPs from those devices. IMO, we should do the first (few) implementations of this feature from the power-domain driver itself, and not try to figure out how to define this for everyone in DT until we have a better handle on it (pun intended) ;) > I don't even know what to say on this. The continual evolution of > OPP bindings continues. This seems like further abuse of DT > power-domains (being a region in a chip that can be powergated) with > Linux PM domains. Agreed. 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
