dts: pwm: npcx: add override mechanism for pwm input clock assignment.

This CL adds a override mechanism for pwm module's input clock source
assignment. If the 'clock-bus' property exists, the NPCX_DT_PROP_ENUM_OR
macro function will return an enum upper token value. Otherwise, it
expands to default value in 'clocks' property.

For example, if the users want to select LFCLK as pwm0's input clock,
ths node can be overridden by adding 'clock-bus' property with an enum
string, "NPCX_CLOCK_BUS_LFCLK".

&pwm0 {
	status = "okay";
	clock-bus = "NPCX_CLOCK_BUS_LFCLK";
};

Signed-off-by: Keith Short <[email protected]>
Signed-off-by: Mulin Chao <[email protected]>

Author: MulinChao

dts/bindings/pwm/nuvoton,npcx-pwm.yaml

@@ -23,6 +23,15 @@ properties:
         description: |
             The PWM output will be configured as open-drain. If not set,
             defaults to push-pull.
+    clock-bus:
+        required: false
+        type: string
+        description: |
+            Select a specific input clock source for the PWM module. If this
+            property doesn't exist, fallback to default value in clocks property.
+        enum:
+            - NPCX_CLOCK_BUS_APB2
+            - NPCX_CLOCK_BUS_LFCLK
 
 pwm-cells:
     - channel

soc/arm/nuvoton_npcx/common/soc_dt.h

@@ -7,6 +7,35 @@
 #ifndef _NUVOTON_NPCX_SOC_DT_H_
 #define _NUVOTON_NPCX_SOC_DT_H_
 
+/**
+ * @brief Like DT_PROP(), but expand parameters with
+ *        DT_ENUM_UPPER_TOKEN not DT_PROP
+ *
+ * If the prop exists, this expands to DT_ENUM_UPPER_TOKEN(node_id, prop).
+ * The default_value parameter is not expanded in this case.
+ *
+ * Otherwise, this expands to default_value.
+ *
+ * @param node_id node identifier
+ * @param prop lowercase-and-underscores property name
+ * @param default_value a fallback value to expand to
+ * @return the property's enum upper token value or default_value
+ */
+#define NPCX_DT_PROP_ENUM_OR(node_id, prop, default_value) \
+	COND_CODE_1(DT_NODE_HAS_PROP(node_id, prop), \
+		    (DT_ENUM_UPPER_TOKEN(node_id, prop)), (default_value))
+
+/**
+ * @brief Like DT_INST_PROP_OR(), but expand parameters with
+ *        NPCX_DT_PROP_ENUM_OR not DT_PROP_OR
+ * @param inst instance number
+ * @param prop lowercase-and-underscores property name
+ * @param default_value a fallback value to expand to
+ * @return the property's enum upper token value or default_value
+ */
+#define NPCX_DT_INST_PROP_ENUM_OR(inst, prop, default_value) \
+	NPCX_DT_PROP_ENUM_OR(DT_DRV_INST(inst), prop, default_value)
+
 /**
  * @brief Construct a npcx_clk_cfg item from first item in 'clocks' prop which
  * type is 'phandle-array' to handle "clock-cells" in current driver.
@@ -27,7 +56,8 @@
  */
 #define NPCX_DT_CLK_CFG_ITEM(inst)                                             \
 	{                                                                      \
-	  .bus  = DT_PHA(DT_DRV_INST(inst), clocks, bus),                      \
+	  .bus  = NPCX_DT_INST_PROP_ENUM_OR(inst, clock_bus,                   \
+				DT_PHA(DT_DRV_INST(inst), clocks, bus)),       \
 	  .ctrl = DT_PHA(DT_DRV_INST(inst), clocks, ctl),                      \
 	  .bit  = DT_PHA(DT_DRV_INST(inst), clocks, bit),                      \
 	}