Qualcomm Technologies QPNP WLED

QPNP (Qualcomm Technologies Plug N Play) WLED (White Light
Emitting Diode) driver is used for controlling display
backlight that is part of PMIC on Qualcomm Technologies
reference platforms. The PMIC is connected to the host
processor via SPMI bus.

Required properties:
- compatible		: should be "qcom,qpnp-wled"
- reg			: base address and size for wled modules
- reg-names		: names associated with base addresses. It
			should be "qpnp-wled-ctrl-base", "qpnp-wled-sink-base",
			"qpnp-wled-ibb-base", "qpnp-wled-lab-base".

Optional properties for WLED:
 - interrupts		: Specifies the interrupts associated with WLED. The available
			  interrupts are over voltage protection(ovp) and short circuit(sc).
			  The values for ovp and sc are <0x3 0xd8 0x1> and <0x3 0xd8 0x2>.
 - interrupt-names	: Specify the interrupt names associated with interrupts. Must be
			  one of "ovp-irq" or "sc-irq"
- linux,name		: name of the wled. default is "wled".
- linux,default-trigger	: trigger for the backlight. default is NONE.
- qcom,fdbk-output	: string feedback current output for wled module. The accepted values
			  are "wled1", "wled2", "wled3", "wled4" and "auto". default is "auto".
- qcom,vref-mv		: maximum reference voltage in mv. default is 350.
- qcom,switch-freq-khz	: switch frequency in khz. default is 800.
- qcom,ovp-mv		: over voltage protection value in mv. default is 17800.
- qcom,ilim-ma		: maximum current limiter in ma. default is 980.
- qcom,boost-duty-ns	: maximum boost duty cycle in ns. default is 104.
- qcom,mod-freq-khz	: modulation frequency in khz. default is 9600.
- qcom,dim-mode		: dimming mode. supporting dimming modes are "analog",
			  "digital", and "hybrid". default is "hybrid".
- qcom,hyb-thres	: threshold value when used in hybrid mode. It represents the
			  percentage of brightntess at which dimming mode is switched
			  from "digital" to "analog". the default value is 6.25%. as the
			  floating point cannot be represented directly, the value is
			  multiplied by 100. so the default is 625.
- qcom,sync-dly-us	: delay for current sync in us. default is 400.
- qcom,fs-curr-ua	: maximum full scale current in ua. default is 25000.
- qcom,en-9b-dim-res	: boolean, specify if 9-bit dim resultion is needed. otherwise 12-bit is used.
- qcom,en-phase-stag	: boolean, specify if phase staggering is needed.
- qcom,en-cabc		: boolean, specify if cabc (content adaptive backlight control) is needed.
- qcom,disp-type-amoled	: specify if the display is amoled
- qcom,led-strings-list	: Wled module has four strings of leds numbered from 0 to 3. each string of leds
			  are operated individually. specify the list of strings used by the device.
			  any combination of led strings can be used. default value is [00 01 02 03]
- qcom,en-ext-pfet-sc-pro : Specify if external pfet short circuit protection is needed
- qcom,cons-sync-write-delay-us : Specify in 'us' the duration of delay between two consecutive writes to
				  SYNC register.

Optional properties if 'qcom,disp-type-amoled' is mentioned in DT:
- qcom,loop-ea-gm	: control the gm for gm stage in control loop. default is 3.
- qcom,loop-comp-res-kohm	: control to select the compensation resistor in kohm. default is 320.
- qcom,vref-psm-mv	: reference psm voltage in mv. default for amoled is 450.
- qcom,sc-deb-cycles	: debounce time for short circuit detection
- qcom,avdd-trim-steps-from-center : The number of steps to trim the OVP threshold voltage. The possible values can be between -7 to 8.

Example:
	qcom,leds@d800 {
		compatible = "qcom,qpnp-wled";
		reg = <0xd800 0x100>,
			<0xd900 0x100>,
			<0xdc00 0x100>,
			<0xde00 0x100>;
		reg-names = "qpnp-wled-ctrl-base",
				"qpnp-wled-sink-base",
				"qpnp-wled-ibb-base",
				"qpnp-wled-lab-base";
		interrupts = <0x3 0xd8 0x2>;
		interrupt-names = "sc-irq";
		status = "okay";
		linux,name = "wled";
		linux,default-trigger = "bkl-trigger";
		qcom,fdbk-output = "auto";
		qcom,vref-mv = <350>;
		qcom,switch-freq-khz = <800>;
		qcom,ovp-mv = <29500>;
		qcom,ilim-ma = <980>;
		qcom,boost-duty-ns = <26>;
		qcom,mod-freq-khz = <9600>;
		qcom,dim-mode = "hybrid";
		qcom,dim-method = "linear";
		qcom,hyb-thres = <625>;
		qcom,sync-dly-us = <800>;
		qcom,fs-curr-ua = <16000>;
		qcom,en-phase-stag;
		qcom,led-strings-list = [00 01 02 03];
		qcom,en-ext-pfet-sc-pro;
	};