iio: 104-quad-8: Add IIO support for the ACCES 104-QUAD-8

The ACCES 104-QUAD-8 is a general purpose quadrature encoder
counter/interface board. The 104-QUAD-8 is capable of monitoring the
outputs of eight encoders via four on-board LSI/CSI LS7266R1 24-bit
dual-axis quadrature counter chips. Core functions handled by the
LS7266R1, such as direction and total count, are available.

Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
also clears the counter's respective error flag. Although the counters
have a 25-bit range, only the lower 24 bits may be set, either directly
or via a counter's preset attribute. Interrupts are not supported by
this driver.

This driver adds IIO support for the ACCES 104-QUAD-8 and ACCES
104-QUAD-4. The base port addresses for the devices may be configured
via the base array module parameter.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8

@@ -0,0 +1,125 @@
+What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_direction_available
+What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_mode_available
+What:		/sys/bus/iio/devices/iio:deviceX/in_count_noise_error_available
+What:		/sys/bus/iio/devices/iio:deviceX/in_count_quadrature_mode_available
+What:		/sys/bus/iio/devices/iio:deviceX/in_index_index_polarity_available
+What:		/sys/bus/iio/devices/iio:deviceX/in_index_synchronous_mode_available
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Discrete set of available values for the respective counter
+		configuration are listed in this file.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_direction
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates whether the counter for
+		channel Y is counting up or down.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_mode
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Count mode for channel Y. Four count modes are available:
+		normal, range limit, non-recycle, and modulo-n. The preset value
+		for channel Y is used by the count mode where required.
+
+		Normal:
+			Counting is continuous in either direction.
+
+		Range Limit:
+			An upper or lower limit is set, mimicking limit switches
+			in the mechanical counterpart. The upper limit is set to
+			the preset value, while the lower limit is set to 0. The
+			counter freezes at count = preset when counting up, and
+			at count = 0 when counting down. At either of these
+			limits, the counting is resumed only when the count
+			direction is reversed.
+
+		Non-recycle:
+			Counter is disabled whenever a 24-bit count overflow or
+			underflow takes place. The counter is re-enabled when a
+			new count value is loaded to the counter via a preset
+			operation or write to raw.
+
+		Modulo-N:
+			A count boundary is set between 0 and the preset value.
+			The counter is reset to 0 at count = preset when
+			counting up, while the counter is set to the preset
+			value at count = 0 when counting down; the counter does
+			not freeze at the bundary points, but counts
+			continuously throughout.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_noise_error
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Read-only attribute that indicates whether excessive noise is
+		present at the channel Y count inputs in quadrature clock mode;
+		irrelevant in non-quadrature clock mode.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_preset
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		If the counter device supports preset registers, the preset
+		count for channel Y is provided by this attribute.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_quadrature_mode
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Configure channel Y counter for non-quadrature or quadrature
+		clock mode. Selecting non-quadrature clock mode will disable
+		synchronous load mode. In quadrature clock mode, the channel Y
+		scale attribute selects the encoder phase division (scale of 1
+		selects full-cycle, scale of 0.5 selects half-cycle, scale of
+		0.25 selects quarter-cycle) processed by the channel Y counter.
+
+		Non-quadrature:
+			The filter and decoder circuit are bypassed. Encoder A
+			input serves as the count input and B as the UP/DOWN
+			direction control input, with B = 1 selecting UP Count
+			mode and B = 0 selecting Down Count mode.
+
+		Quadrature:
+			Encoder A and B inputs are digitally filtered and
+			decoded for UP/DN clock.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_set_to_preset_on_index
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Whether to set channel Y counter with channel Y preset value
+		when channel Y index input is active, or continuously count.
+		Valid attribute values are boolean.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_index_polarity
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Active level of channel Y index input; irrelevant in
+		non-synchronous load mode.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_synchronous_mode
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Configure channel Y counter for non-synchronous or synchronous
+		load mode. Synchronous load mode cannot be selected in
+		non-quadrature clock mode.
+
+		Non-synchronous:
+			A logic low level is the active level at this index
+			input. The index function (as enabled via
+			set_to_preset_on_index) is performed directly on the
+			active level of the index input.
+
+		Synchronous:
+			Intended for interfacing with encoder Index output in
+			quadrature clock mode. The active level is configured
+			via index_polarity. The index function (as enabled via
+			set_to_preset_on_index) is performed synchronously with
+			the quadrature clock on the active level of the index
+			input.

MAINTAINERS

@@ -255,6 +255,12 @@ L:	linux-gpio@vger.kernel.org
 S:	Maintained
 F:	drivers/gpio/gpio-104-idio-16.c
 
+ACCES 104-QUAD-8 IIO DRIVER
+M:	William Breathitt Gray <vilhelm.gray@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/iio/counter/104-quad-8.c
+
 ACENIC DRIVER
 M:	Jes Sorensen <jes@trained-monkey.org>
 L:	linux-acenic@sunsite.dk

drivers/iio/Kconfig

@@ -73,6 +73,7 @@ source "drivers/iio/adc/Kconfig"
 source "drivers/iio/amplifiers/Kconfig"
 source "drivers/iio/chemical/Kconfig"
 source "drivers/iio/common/Kconfig"
+source "drivers/iio/counter/Kconfig"
 source "drivers/iio/dac/Kconfig"
 source "drivers/iio/dummy/Kconfig"
 source "drivers/iio/frequency/Kconfig"

drivers/iio/Makefile

@@ -18,6 +18,7 @@ obj-y += amplifiers/
 obj-y += buffer/
 obj-y += chemical/
 obj-y += common/
+obj-y += counter/
 obj-y += dac/
 obj-y += dummy/
 obj-y += gyro/

drivers/iio/counter/Kconfig

@@ -0,0 +1,24 @@
+#
+# Counter devices
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Counters"
+
+config 104_QUAD_8
+	tristate "ACCES 104-QUAD-8 driver"
+	depends on X86 && ISA_BUS_API
+	help
+	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
+	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).
+
+	  Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
+	  also clears the counter's respective error flag. Although the counters
+	  have a 25-bit range, only the lower 24 bits may be set, either directly
+	  or via a counter's preset attribute. Interrupts are not supported by
+	  this driver.
+
+	  The base port addresses for the devices may be configured via the base
+	  array module parameter.
+
+endmenu

drivers/iio/counter/Makefile

@@ -0,0 +1,7 @@
+#
+# Makefile for IIO counter devices
+#
+
+# When adding new entries keep the list in alphabetical order
+
+obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o