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Groups > linux.kernel > #1363908

[PATCH v5 02/21] PM / devfreq: exynos: Add documentation for generic exynos bus frequency driver

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This patch adds the documentation for generic exynos bus frequency
driver.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
---
 .../devicetree/bindings/devfreq/exynos-bus.txt     | 95 ++++++++++++++++++++++
 1 file changed, 95 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..78171b918e3f
--- /dev/null
+++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
@@ -0,0 +1,95 @@
+* Generic Exynos Bus frequency device
+
+The Samsung Exynos SoC has many buses for data transfer between DRAM
+and sub-blocks in SoC. Most Exynos SoCs share the common architecture
+for buses. Generally, each bus of Exynos SoC includes a source clock
+and a power line, which are able to change the clock frequency
+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.
+
+There are a little different composition among Exynos SoC because each Exynos
+SoC has different sub-blocks. Therefore, shch 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.
+- 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 current utilization
+  of buses.
+
+Optional properties for 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
+			which is used to calculate the max voltage.
+
+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 |825000   |
+	|L5| 400000 |875000   |
+	-----------------------
+
+Example2 :
+	The bus of DMC (Dynamic Memory Controller) block in exynos3250.dtsi
+	is listed below:
+
+	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_table1 {
+		compatible = "operating-points-v2";
+		opp-shared;
+
+		opp@50000000 {
+			opp-hz = /bits/ 64 <50000000>;
+			opp-microvolt = <800000>;
+		};
+		opp@100000000 {
+			opp-hz = /bits/ 64 <100000000>;
+			opp-microvolt = <800000>;
+		};
+		opp@134000000 {
+			opp-hz = /bits/ 64 <134000000>;
+			opp-microvolt = <800000>;
+		};
+		opp@200000000 {
+			opp-hz = /bits/ 64 <200000000>;
+			opp-microvolt = <825000>;
+		};
+		opp@400000000 {
+			opp-hz = /bits/ 64 <400000000>;
+			opp-microvolt = <875000>;
+		};
+	};
+
+	Usage case to handle the frequency and voltage of bus on runtime
+	in exynos3250-rinato.dts is listed below:
+
+	&bus_dmc {
+		devfreq-events = <&ppmu_dmc0_3>, <&ppmu_dmc1_3>;
+		vdd-supply = <&buck1_reg>;	/* VDD_MIF */
+		status = "okay";
+	};
-- 
1.9.1

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[PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency driver  and new passive governor Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:30 +0100
  [PATCH v5 15/21] ARM: dts: Add bus nodes using VDD_MIF for Exynos4x12 Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:30 +0100
  [PATCH v5 20/21] ARM: dts: Expand the voltage range of buck1/3  regulator for exynos4412-odroidu3 Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:30 +0100
  [PATCH v5 16/21] ARM: dts: Add bus nodes using VDD_INT for Exynos4x12 Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:30 +0100
  [PATCH v5 02/21] PM / devfreq: exynos: Add documentation for generic  exynos bus frequency driver Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:30 +0100
  [PATCH v5 07/21] PM / devfreq: exynos: Add support of bus frequency of  sub-blocks using passive governor Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:40 +0100
  [PATCH v5 09/21] PM / devfreq: exynos: Add the detailed correlation  between sub-blocks and power line Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:40 +0100
  Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:40 +0100
    Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Markus Reichl <m.reichl@fivetechno.de> - 2016-03-24 14:50 +0100
      Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Tobias Jakobi <tjakobi@math.uni-bielefeld.de> - 2016-03-24 15:00 +0100
        Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Chanwoo Choi <cwchoi00@gmail.com> - 2016-03-24 15:20 +0100
      Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Chanwoo Choi <cwchoi00@gmail.com> - 2016-03-24 15:30 +0100
    Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Anand Moon <linux.amoon@gmail.com> - 2016-03-27 14:30 +0200
      Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Chanwoo Choi <cwchoi00@gmail.com> - 2016-03-27 16:00 +0200
  [PATCH v5 11/21] MAINTAINERS: Add samsung bus frequency driver entry Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:40 +0100
  [PATCH v5 05/21] PM / devfreq: Add governer type with unique number Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:40 +0100
  [PATCH v5 13/21] ARM: dts: Add DMC bus frequency for  exynos3250-rinato/monk Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:40 +0100
  [PATCH v5 04/21] PM / devfreq: Add new DEVFREQ_TRANSITION_NOTIFIER  notifier Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-24 05:40 +0100
  Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Markus Reichl <m.reichl@fivetechno.de> - 2016-03-24 15:40 +0100
    Re: [PATCH v5 00/21] PM / devferq: Add generic exynos bus frequency  driver and new passive governor Chanwoo Choi <cw00.choi@samsung.com> - 2016-03-25 00:40 +0100

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