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