Hi, On 2015년 12월 10일 09:39, Krzysztof Kozlowski wrote: > On 09.12.2015 13:07, Chanwoo Choi wrote: >> This patch adds the documentation for generic exynos bus frequency >> driver. >> >> Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx> >> --- >> .../devicetree/bindings/devfreq/exynos-bus.txt | 94 ++++++++++++++++++++++ >> 1 file changed, 94 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> >> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> new file mode 100644 >> index 000000000000..54a1f9c46c88 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt >> @@ -0,0 +1,94 @@ >> +* Generic Exynos Bus frequency device >> + >> +The Samsung Exynos SoC have many buses for data transfer between DRAM >> +and sub-blocks in SoC. Almost Exynos SoC have the common architecture >> +for buses. Generally, the each bus of Exynos SoC includes the source clock >> +and power line and then is able to change the clock according to the usage >> +of each buses on runtime. When gathering the usage of each buses on runtime, >> +thie driver uses the PPMU (Platform Performance Monitoring Unit) which > > s/thie/the/ OK. > >> +is able to measure the current load of sub-blocks. >> + >> +There are a little different composition among Exynos SoC because each Exynos >> +SoC has the different sub-blocks. So, this difference should be specified >> +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: >> +- 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. >> +- #clock-cells: should be 1. > > This is a clock consumer, right? So the clock-cells is not valid here. You're right. I'll remove '#clock-cells'. > >> +- operating-points-v2: the OPP table including frequency/voltage information >> + to support DVFS (Dynamic Voltage/Frequency Scaling) feature. >> +- vdd-supply: the regulator to provide the buses with the voltage. >> +- devfreq-events: the devfreq-event device to monitor the curret utilization > > s/curret/current/ > >> + of buses. >> + >> +Optional properties for bus device: >> +- exynos,saturation-ratio: the percentage value which is used to calibrate >> + the performance count againt total cycle count. > > s/againt/against/ OK. > >> + >> +Example1: >> + Show the AXI buses of Exynos3250 SoC. Exynos3250 divides the buses to >> + power line (regulator). The MIF (Memory Interface) AXI bus is used to >> + transfer data between DRAM and CPU and uses the VDD_MIF regualtor. >> + >> + - power line(VDD_MIF) --> bus for DMC (Dynamic Memory Controller) block >> + >> + - MIF bus's frequency/voltage table >> + ----------------------- >> + |Lv| Freq | Voltage | >> + ----------------------- >> + |L1| 50000 |800000 | >> + |L2| 100000 |800000 | >> + |L3| 134000 |800000 | >> + |L4| 200000 |800000 | >> + |L5| 400000 |875000 | >> + ----------------------- >> + >> +Example2 : >> + The bus of DMC (Dynamic Memory Controller) block in exynos3250.dtsi >> + are listed below: > > s/are/is/ (one bus is listed) OK. > >> + >> + bus_dmc: bus_dmc { >> + compatible = "samsung,exynos-bus"; >> + clocks = <&cmu_dmc CLK_DIV_DMC>; >> + clock-names = "bus"; >> + operating-points-v2 = <&bus_dmc_opp_table>; >> + status = "disabled"; >> + }; >> + >> + bus_dmc_opp_table: opp_table0 { >> + compatible = "operating-points-v2"; >> + opp-shared; >> + >> + opp00 { > > Maybe use convention with frequency, like: > opp@50000000 > This also used in opp.txt examples. In the Documentations/devicetree/bindings/opp/opp.txt, the example uses the 'opp@0x'. I check the opp.txt of Linux 4.4-rc4. > > >> + opp-hz = /bits/ 64 <50000000>; >> + opp-microvolt = <800000>; >> + }; >> + opp01 { >> + opp-hz = /bits/ 64 <100000000>; >> + opp-microvolt = <800000>; >> + }; >> + opp02 { >> + opp-hz = /bits/ 64 <134000000>; >> + opp-microvolt = <800000>; >> + }; >> + opp03 { >> + opp-hz = /bits/ 64 <200000000>; >> + opp-microvolt = <800000>; >> + }; >> + opp04 { >> + opp-hz = /bits/ 64 <400000000>; >> + opp-microvolt = <875000>; >> + }; >> + }; >> + >> + Usage case to handle the frequency and voltage of bus on runtime >> + in exynos3250-rinato.dts are listed below: > > s/are/is/ OK. > >> + >> + &bus_dmc { >> + devfreq-events = <&ppmu_dmc0_3>, <&ppmu_dmc1_3>; >> + vdd-supply = <&buck1_reg>; /* VDD_MIF */ >> + status = "okay"; >> + }; Thanks for your review. 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