[RFC PATCH 2/4] devfreq: exynos: Add documentation for generic exynos memory bus frequency driver

[Chanwoo Choi]

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

Cc: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
---
 .../devicetree/bindings/devfreq/exynos-busfreq.txt | 184 +++++++++++++++++++++
 1 file changed, 184 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/devfreq/exynos-busfreq.txt

diff --git a/Documentation/devicetree/bindings/devfreq/exynos-busfreq.txt b/Documentation/devicetree/bindings/devfreq/exynos-busfreq.txt
new file mode 100644
index 0000000..c601e88
--- /dev/null
+++ b/Documentation/devicetree/bindings/devfreq/exynos-busfreq.txt
@@ -0,0 +1,184 @@
+
+* Generic Exynos Memory Bus device
+
+The Samsung Exynos SoCs have many memory buses for data transfer between DRAM
+memory and MMC/sub-IP in SoC. Almost Exynos SoCs have the common architecture
+for memory buses. Generally, Exynos SoC express the memory bus by using memory
+bus group and block. The memory bus group has one more memory bus blocks and
+OPP table (including frequency and voltage for DVFS), regulator, devfreq-event
+devices. Each memory bus block has a clock for own memory bus speen and
+frequency table for DVFS. There are a little different among Exynos SoCs
+because each Exynos SoC has the different sub-IP and differnt memory bus.
+So, this difference should be specified in devicetree file.
+
+Required properties for memory bus group:
+- compatible: Should be "samsung,exynos-memory-bus".
+- operating-points: the OPP table including frequency/voltage information to
+                  support DVFS (Dynamic Voltage/Frequency Scaling) feature.
+- devfreq-events: the devfreq-event device to monitor the curret state of
+                  memory bus group.
+- vdd-mem-supply: the regulator to provide memory bus group with the voltage.
+
+Required properties for memory bus block:
+- clock-names : the name of clock used by the memory bus, "memory-bus".
+- clocks : phandles for clock specified in "clock-names" property.
+- #clock-cells: should be 1.
+- frequency: the frequency table to support DVFS feature.
+
+Example1 : Memory bus group/block in exynos3250.dtsi are listed below.
+	Exynos3250 has two memory bus group (MIF, INT group). MIF memory bus
+	group includes one memory bus block between DRAM and eMMC. Also, INT
+	memory bus group includes eight memory bus blocks which support each
+	sub-IPs between DRAM and sub-IPs.
+
+	memory_bus_mif: memory_bus@0 {
+		compatible = "samsung,exynos-memory-bus";
+
+		operating-points = <
+			400000 875000
+			200000 800000
+			133000 800000
+			100000 800000
+			50000  800000>;
+		status = "disabled";
+
+		blocks {
+			dmc_block: memory_bus_block1 {
+				clocks = <&cmu_dmc CLK_DIV_DMC>;
+				clock-names = "memory-bus";
+				frequency = <
+					400000
+					200000
+					133000
+					100000
+					50000>;
+			};
+		};
+	};
+
+	memory_bus_int: memory_bus@1 {
+		compatible = "samsung,exynos-memory-bus";
+
+		operating-points = <
+			400000 950000
+			200000 950000
+			133000 925000
+			100000 850000
+			80000  850000
+			50000  850000>;
+
+		status = "disabled";
+
+		blocks {
+			peri_block: memory_bus_block1 {
+				clocks = <&cmu CLK_DIV_ACLK_100>;
+				clock-names = "memory-bus";
+				frequency = <
+					100000
+					100000
+					100000
+					100000
+					50000
+					50000>;
+			};
+
+			display_block: memory_bus_block2 {
+				clocks = <&cmu CLK_DIV_ACLK_160>;
+				clock-names = "memory-bus";
+				frequency = <
+					200000
+					160000
+					100000
+					80000
+					80000
+					50000>;
+			};
+
+			isp_block: memory_bus_block3 {
+				clocks = <&cmu CLK_DIV_ACLK_200>;
+				clock-names = "memory-bus";
+				frequency = <
+					200000
+					200000
+					100000
+					80000
+					50000
+					50000>;
+			};
+
+			gps_block: memory_bus_block4 {
+				clocks = <&cmu CLK_DIV_ACLK_266>;
+				clock-names = "memory-bus";
+				frequency = <
+					300000
+					200000
+					133000
+					100000
+					50000
+					50000>;
+			};
+
+			mcuisp_block: memory_bus_block5 {
+				clocks = <&cmu CLK_DIV_ACLK_400_MCUISP>;
+				clock-names = "memory-bus";
+				frequency = <
+					400000
+					200000
+					50000
+					50000
+					50000
+					50000>;
+			};
+
+			leftbus_block: memory_bus_block6 {
+				clocks = <&cmu CLK_DIV_GDL>;
+				clock-names = "memory-bus";
+				frequency = <
+					200000
+					200000
+					133000
+					100000
+					100000
+					100000>;
+			};
+
+			rightbus_block: memory_bus_block7 {
+				clocks = <&cmu CLK_DIV_GDR>;
+				clock-names = "memory-bus";
+				frequency = <
+					200000
+					200000
+					133000
+					100000
+					100000
+					100000>;
+			};
+
+			mfc_block: memory_bus_block8 {
+				clocks = <&cmu CLK_SCLK_MFC>;
+				clock-names = "memory-bus";
+				frequency = <
+					200000
+					200000
+					200000
+					133000
+					100000
+					80000>;
+			};
+		};
+	};
+
+Example2 : Usage case to handle the frequency/voltage of memory bus on runtime
+	in exynos3250-rinato.dts are listed below.
+
+	&memory_bus_mif {
+		devfreq-events = <&ppmu_dmc0_3>, <&ppmu_dmc1_3>;
+		vdd-mem-supply = <&buck1_reg>;
+		status = "okay";
+	};
+
+	&memory_bus_int {
+		devfreq-events = <&ppmu_leftbus_3>, <&ppmu_rightbus_3>;
+		vdd-mem-supply = <&buck3_reg>;
+		status = "okay";
+	};
-- 
1.8.5.5

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