pwm: Add TI PWM subsystem driver

In some platforms (like am33xx), PWM sub modules (ECAP, EHRPWM, EQEP)
are integrated to PWM subsystem. These PWM submodules has resources
shared and only one register bit-field is provided to control
module/clock enable/disable, makes it difficult to handle common
resources from independent PWMSS submodule drivers.

So the solution here implemented in this patch is, to create driver for
PWMSS and take the role of parent driver for PWM submodules. PWMSS
parent driver enumerates all the child nodes under PWMSS module. Also
symbol "pwmss_submodule_state_change" exported to enable clock gating
for individual PWMSS submodules, and submodule drivers has to enable
clock gating from their drivers.

As this is only supported during DT boot, the parent/child relationship
is created and populated in DT execution flow. The only required change
is inside DTS file, making EHRPWM & ECAP as a child to PWMSS node.

Signed-off-by: Philip, Avinash <avinashphilip@ti.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

1 files changed, 31 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt b/Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt
new file mode 100644
index 0000000..f7eae77
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt
@@ -0,0 +1,31 @@
+TI SOC based PWM Subsystem
+
+Required properties:
+- compatible: Must be "ti,am33xx-pwmss";
+- reg: physical base address and size of the registers map.
+- address-cells: Specify the number of u32 entries needed in child nodes.
+		  Should set to 1.
+- size-cells: specify number of u32 entries needed to specify child nodes size
+		in reg property. Should set to 1.
+- ranges: describes the address mapping of a memory-mapped bus. Should set to
+	   physical address map of child's base address, physical address within
+	   parent's address  space and length of the address map. For am33xx,
+	   3 set of child register maps present, ECAP register space, EQEP
+	   register space, EHRPWM register space.
+
+Also child nodes should also populated under PWMSS DT node.
+
+Example:
+pwmss0: pwmss@48300000 {
+	compatible = "ti,am33xx-pwmss";
+	reg = <0x48300000 0x10>;
+	ti,hwmods = "epwmss0";
+	#address-cells = <1>;
+	#size-cells = <1>;
+	status = "disabled";
+	ranges = <0x48300100 0x48300100 0x80   /* ECAP */
+		  0x48300180 0x48300180 0x80   /* EQEP */
+		  0x48300200 0x48300200 0x80>; /* EHRPWM */
+
+	/* child nodes go here */
+};