leds: Add driver for Qualcomm LPG

The Light Pulse Generator (LPG) is a PWM-block found in a wide range of
PMICs from Qualcomm. These PMICs typically comes with 1-8 LPG instances,
with their output being routed to various other components, such as
current sinks or GPIOs.

Each LPG instance can operate on fixed parameters or based on a shared
lookup-table, altering the duty cycle over time. This provides the means
for hardware assisted transitions of LED brightness.

A typical use case for the fixed parameter mode is to drive a PWM
backlight control signal, the driver therefor allows each LPG instance
to be exposed to the kernel either through the LED framework or the PWM
framework.

A typical use case for the LED configuration is to drive RGB LEDs in
smartphones etc, for which the driver support multiple channels to be
ganged up to a MULTICOLOR LED. In this configuration the pattern
generators will be synchronized, to allow for multi-color patterns.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/leds/Kconfig

@@ -933,6 +933,9 @@ source "drivers/leds/blink/Kconfig"
 comment "Flash and Torch LED drivers"
 source "drivers/leds/flash/Kconfig"
 
+comment "RGB LED drivers"
+source "drivers/leds/rgb/Kconfig"
+
 comment "LED Triggers"
 source "drivers/leds/trigger/Kconfig"
 

drivers/leds/Makefile

@@ -106,6 +106,9 @@ obj-$(CONFIG_LEDS_USER)			+= uleds.o
 # Flash and Torch LED Drivers
 obj-$(CONFIG_LEDS_CLASS_FLASH)		+= flash/
 
+# RGB LED Drivers
+obj-$(CONFIG_LEDS_CLASS_MULTICOLOR)	+= rgb/
+
 # LED Triggers
 obj-$(CONFIG_LEDS_TRIGGERS)		+= trigger/
 

drivers/leds/rgb/Kconfig

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0
+
+if LEDS_CLASS_MULTICOLOR
+
+config LEDS_QCOM_LPG
+	tristate "LED support for Qualcomm LPG"
+	depends on OF
+	depends on SPMI
+	help
+	  This option enables support for the Light Pulse Generator found in a
+	  wide variety of Qualcomm PMICs.
+
+endif # LEDS_CLASS_MULTICOLOR

drivers/leds/rgb/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_LEDS_QCOM_LPG)	+= leds-qcom-lpg.o