counter: new TI eQEP driver

This adds a new counter driver for the Texas Instruments Enhanced
Quadrature Encoder Pulse (eQEP) module.

Only very basic functionality is currently implemented - only enough to
be able to read the position. The actual device has many more features
which can be added to the driver on an as-needed basis.

It is not possible to read the QEPA/B signal values in hardware, so
that feature is omitted.

The TI_PWMSS kernel option is selected in Kconfig to enable the parent
bus, which is needed for power management.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

MAINTAINERS

@@ -16202,6 +16202,12 @@ S:	Maintained
 F:	drivers/media/platform/davinci/
 F:	include/media/davinci/
 
+TI ENHANCED QUADRATURE ENCODER PULSE (eQEP) DRIVER
+R:	David Lechner <david@lechnology.com>
+L:	linux-iio@vger.kernel.org
+F:	Documentation/devicetree/bindings/counter/ti-eqep.yaml
+F:	drivers/counter/ti-eqep.c
+
 TI ETHERNET SWITCH DRIVER (CPSW)
 R:	Grygorii Strashko <grygorii.strashko@ti.com>
 L:	linux-omap@vger.kernel.org

drivers/bus/Kconfig

@@ -152,7 +152,7 @@ config TEGRA_GMI
 
 config  TI_PWMSS
 	bool
-	default y if (ARCH_OMAP2PLUS) && (PWM_TIECAP || PWM_TIEHRPWM)
+	default y if (ARCH_OMAP2PLUS) && (PWM_TIECAP || PWM_TIEHRPWM || TI_EQEP)
 	help
 	  PWM Subsystem driver support for AM33xx SOC.
 

drivers/counter/Kconfig

@@ -49,6 +49,17 @@ config STM32_LPTIMER_CNT
 	  To compile this driver as a module, choose M here: the
 	  module will be called stm32-lptimer-cnt.
 
+config TI_EQEP
+	tristate "TI eQEP counter driver"
+	depends on (SOC_AM33XX || COMPILE_TEST)
+	select REGMAP_MMIO
+	help
+	  Select this option to enable the Texas Instruments Enhanced Quadrature
+	  Encoder Pulse (eQEP) counter driver.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ti-eqep.
+
 config FTM_QUADDEC
 	tristate "Flex Timer Module Quadrature decoder driver"
 	depends on HAS_IOMEM && OF

drivers/counter/Makefile

@@ -8,4 +8,5 @@ obj-$(CONFIG_COUNTER) += counter.o
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
 obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o
 obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
+obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
 obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o