On 2016년 04월 12일 16:34, Krzysztof Kozlowski wrote: > 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/ I'll fix it on patch2 because this typo happen on patch2. > >> 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/ ditto. > > > Acked-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx> Thanks for your review. Best Regards, Chanwoo Choi -- 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
