On 04/11/2016 05:57 AM, Chanwoo Choi wrote: > This patch updates the documentation for passive bus devices and adds the > detailed example of Exynos3250. > > Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx> > Acked-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> > --- > .../devicetree/bindings/devfreq/exynos-bus.txt | 250 ++++++++++++++++++++- > 1 file changed, 247 insertions(+), 3 deletions(-) > > diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt > index 78171b918e3f..03f13d38f1a1 100644 > --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt > +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt > @@ -8,22 +8,46 @@ of the bus in runtime. To monitor the usage of each bus in runtime, > the driver uses the PPMU (Platform Performance Monitoring Unit), which > is able to measure the current load of sub-blocks. > > +The Exynos SoC includes the various sub-blocks which have the each AXI bus. > +The each AXI bus has the owned source clock but, has not the only owned > +power line. The power line might be shared among one more sub-blocks. > +So, we can divide into two type of device as the role of each sub-block. > +There are two type of bus devices as following: > +- parent bus device > +- passive bus device > + > +Basically, parent and passive bus device share the same power line. > +The parent bus device can only change the voltage of shared power line > +and the rest bus devices (passive bus device) depend on the decision of > +the parent bus device. If there are three blocks which share the VDD_xxx > +power line, Only one block should be parent device and then the rest blocks > +should depend on the parent device as passive device. > + > + VDD_xxx |--- A block (parent) > + |--- B block (passive) > + |--- C block (passive) > + > There are a little different composition among Exynos SoC because each Exynos > SoC has different sub-blocks. Therefore, shch difference should be specified s/shch/such/ > in devicetree file instead of each device driver. In result, this driver > is able to support the bus frequency for all Exynos SoCs. > > -Required properties for bus device: > +Required properties for all bus devices: > - compatible: Should be "samsung,exynos-bus". > - clock-names : the name of clock used by the bus, "bus". > - clocks : phandles for clock specified in "clock-names" property. > - operating-points-v2: the OPP table including frequency/voltage information > to support DVFS (Dynamic Voltage/Frequency Scaling) feature. > + > +Required properties only for parent bus device: > - vdd-supply: the regulator to provide the buses with the voltage. > - devfreq-events: the devfreq-event device to monitor the current utilization > of buses. > > -Optional properties for bus device: > +Required properties only for passive bus device: > +- devfreq: the parent bus device. > + > +Optional properties only for parent bus device: > - exynos,saturation-ratio: the percentage value which is used to calibrate > the performance count against total cycle count. > - exynos,voltage-tolerance: the percentage value for bus voltage tolerance > @@ -34,7 +58,20 @@ Example1: > power line (regulator). The MIF (Memory Interface) AXI bus is used to > transfer data between DRAM and CPU and uses the VDD_MIF regualtor. s/regualtor/regulator/ Acked-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx> Best regards, Krzysztof -- 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
