clk: shmobile: rz: Add CPG/MSTP Clock Domain support

Add Clock Domain support to the RZ Clock Pulse Generator (CPG) driver
using the generic PM Domain. This allows to power-manage the module
clocks of SoC devices that are part of the CPG/MSTP Clock Domain using
Runtime PM, or for system suspend/resume.

SoC devices that are part of the CPG/MSTP Clock Domain and can be
power-managed through an MSTP clock should be tagged in DT with a proper
"power-domains" property.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Stephen Boyd <[e-mail]>
Reviewed-by: Ulf Hansson <[e-mail]>
Signed-off-by: Simon Horman <[e-mail]>

Documentation/devicetree/bindings/clock/renesas,rz-cpg-clocks.txt

···
 
 The CPG generates core clocks for the RZ SoCs. It includes the PLL, variable
 CPU and GPU clocks, and several fixed ratio dividers.
+The CPG also provides a Clock Domain for SoC devices, in combination with the
+CPG Module Stop (MSTP) Clocks.
 
 Required Properties:
 
···
   - #clock-cells: Must be 1
   - clock-output-names: The names of the clocks. Supported clocks are "pll",
     "i", and "g"
+  - #power-domain-cells: Must be 0
+
+SoC devices that are part of the CPG/MSTP Clock Domain and can be power-managed
+through an MSTP clock should refer to the CPG device node in their
+"power-domains" property, as documented by the generic PM domain bindings in
+Documentation/devicetree/bindings/power/power_domain.txt.
 
 
-Example
--------
+Examples
+--------
+
+  - CPG device node:
 
 	cpg_clocks: cpg_clocks@fcfe0000 {
 		#clock-cells = <1>;
···
 		reg = <0xfcfe0000 0x18>;
 		clocks = <&extal_clk>, <&usb_x1_clk>;
 		clock-output-names = "pll", "i", "g";
+		#power-domain-cells = <0>;
+	};
+
+
+  - CPG/MSTP Clock Domain member device node:
+
+	mtu2: timer@fcff0000 {
+		compatible = "renesas,mtu2-r7s72100", "renesas,mtu2";
+		reg = <0xfcff0000 0x400>;
+		interrupts = <0 107 IRQ_TYPE_LEVEL_HIGH>;
+		interrupt-names = "tgi0a";
+		clocks = <&mstp3_clks R7S72100_CLK_MTU2>;
+		clock-names = "fck";
+		power-domains = <&cpg_clocks>;
+		status = "disabled";
 	};

arch/arm/mach-shmobile/Kconfig

···
 
 config ARCH_R7S72100
 	bool "RZ/A1H (R7S72100)"
+	select PM_GENERIC_DOMAINS if PM
 	select SYS_SUPPORTS_SH_MTU2
 
 config ARCH_R8A73A4

drivers/clk/shmobile/clk-rz.c

···
  */
 
 #include <linux/clk-provider.h>
+#include <linux/clk/shmobile.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/of.h>
···
 	}
 
 	of_clk_add_provider(np, of_clk_src_onecell_get, &cpg->data);
+
+	cpg_mstp_add_clk_domain(np);
 }
 CLK_OF_DECLARE(rz_cpg_clks, "renesas,rz-cpg-clocks", rz_cpg_clocks_init);