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linux/Documentation/ABI/testing/sysfs-bus-counter
William Breathitt Gray d428487471 counter: i8254: Introduce the Intel 8254 interface library module 
Exposes consumer library functions providing support for interfaces
compatible with the venerable Intel 8254 Programmable Interval Timer
(PIT).

The Intel 8254 PIT first appeared in the early 1980s and was used
initially in IBM PC compatibles. The popularity of the original Intel
825x family of chips led to many subsequent variants and clones of the
interface in various chips and integrated circuits. Although still
popular, interfaces compatible with the Intel 8254 PIT are nowdays
typically found embedded in larger VLSI processing chips and FPGA
components rather than as discrete ICs.

A CONFIG_I8254 Kconfig option is introduced by this patch. Modules
wanting access to these i8254 library functions should select this
Kconfig option, and import the I8254 symbol namespace.

Link: https://lore.kernel.org/r/f6fe32c2db9525d816ab1a01f45abad56c081652.1681665189.git.william.gray@linaro.org/
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
2023-06-08 10:11:17 -04:00

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What: /sys/bus/counter/devices/counterX/cascade_counts_enable
KernelVersion: 6.4
Contact: linux-iio@vger.kernel.org
Description:
Indicates the cascading of Counts on Counter X.
Valid attribute values are boolean.
What: /sys/bus/counter/devices/counterX/external_input_phase_clock_select
KernelVersion: 6.4
Contact: linux-iio@vger.kernel.org
Description:
Selects the external clock pin for phase counting mode of
Counter X.
MTCLKA-MTCLKB:
MTCLKA and MTCLKB pins are selected for the external
phase clock.
MTCLKC-MTCLKD:
MTCLKC and MTCLKD pins are selected for the external
phase clock.
What: /sys/bus/counter/devices/counterX/external_input_phase_clock_select_available
KernelVersion: 6.4
Contact: linux-iio@vger.kernel.org
Description:
Discrete set of available values for the respective device
configuration are listed in this file.
What: /sys/bus/counter/devices/counterX/countY/count
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Count data of Count Y represented as a string.
What: /sys/bus/counter/devices/counterX/countY/capture
KernelVersion: 6.1
Contact: linux-iio@vger.kernel.org
Description:
Historical capture of the Count Y count data.
What: /sys/bus/counter/devices/counterX/countY/ceiling
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Count value ceiling for Count Y. This is the upper limit for the
respective counter.
What: /sys/bus/counter/devices/counterX/countY/floor
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Count value floor for Count Y. This is the lower limit for the
respective counter.
What: /sys/bus/counter/devices/counterX/countY/count_mode
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Count mode for channel Y. The ceiling and floor values for
Count Y are used by the count mode where required. The following
count modes are available:
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 Count Y ceiling value, while the lower limit is set
to the Count Y floor value. The counter freezes at
count = ceiling when counting up, and at count = floor
when counting down. At either of these limits, the
counting is resumed only when the count direction is
reversed.
non-recycle:
The counter is disabled whenever a counter 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 direct write.
modulo-n:
A count value boundary is set between the Count Y floor
value and the Count Y ceiling value. The counter is
reset to the Count Y floor value at count = ceiling when
counting up, while the counter is set to the Count Y
ceiling value at count = floor when counting down; the
counter does not freeze at the boundary points, but
counts continuously throughout.
interrupt on terminal count:
The output signal is initially low, and will remain low
until the counter reaches zero. The output signal then
goes high and remains high until a new preset value is
set.
hardware retriggerable one-shot:
The output signal is initially high. The output signal
will go low by a trigger input signal, and will remain
low until the counter reaches zero. The output will then
go high and remain high until the next trigger. A
trigger results in loading the counter to the preset
value and setting the output signal low, thus starting
the one-shot pulse.
rate generator:
The output signal is initially high. When the counter
has decremented to 1, the output signal goes low for one
clock pulse. The output signal then goes high again, the
counter is reloaded to the preset value, and the process
repeats in a periodic manner as such.
square wave mode:
The output signal is initially high.
If the initial count is even, the counter is decremented
by two on succeeding clock pulses. When the count
expires, the output signal changes value and the
counter is reloaded to the preset value. The process
repeats in periodic manner as such.
If the initial count is odd, the initial count minus one
(an even number) is loaded and then is decremented by
two on succeeding clock pulses. One clock pulse after
the count expires, the output signal goes low and the
counter is reloaded to the preset value minus one.
Succeeding clock pulses decrement the count by two. When
the count expires, the output goes high again and the
counter is reloaded to the preset value minus one. The
process repeats in a periodic manner as such.
software triggered strobe:
The output signal is initially high. When the count
expires, the output will go low for one clock pulse and
then go high again. The counting sequence is "triggered"
by setting the preset value.
hardware triggered strobe:
The output signal is initially high. Counting is started
by a trigger input signal. When the count expires, the
output signal will go low for one clock pulse and then
go high again. A trigger results in loading the counter
to the preset value.
What: /sys/bus/counter/devices/counterX/countY/count_mode_available
What: /sys/bus/counter/devices/counterX/countY/error_noise_available
What: /sys/bus/counter/devices/counterX/countY/function_available
What: /sys/bus/counter/devices/counterX/countY/prescaler_available
What: /sys/bus/counter/devices/counterX/countY/signalZ_action_available
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Discrete set of available values for the respective Count Y
configuration are listed in this file. Values are delimited by
newline characters.
What: /sys/bus/counter/devices/counterX/countY/direction
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the count direction of Count
Y. Two count directions are available: forward and backward.
Some counter devices are able to determine the direction of
their counting. For example, quadrature encoding counters can
determine the direction of movement by evaluating the leading
phase of the respective A and B quadrature encoding signals.
This attribute exposes such count directions.
What: /sys/bus/counter/devices/counterX/countY/enable
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Whether channel Y counter is enabled. Valid attribute values are
boolean.
This attribute is intended to serve as a pause/unpause mechanism
for Count Y. Suppose a counter device is used to count the total
movement of a conveyor belt: this attribute allows an operator
to temporarily pause the counter, service the conveyor belt,
and then finally unpause the counter to continue where it had
left off.
What: /sys/bus/counter/devices/counterX/countY/error_noise
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates whether excessive noise is
present at the channel Y counter inputs.
What: /sys/bus/counter/devices/counterX/countY/function
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Count function mode of Count Y; count function evaluation is
triggered by conditions specified by the Count Y signalZ_action
attributes. The following count functions are available:
increase:
Accumulated count is incremented.
decrease:
Accumulated count is decremented.
pulse-direction:
Rising edges on signal A updates the respective count.
The input level of signal B determines direction.
quadrature x1 a:
If direction is forward, rising edges on quadrature pair
signal A updates the respective count; if the direction
is backward, falling edges on quadrature pair signal A
updates the respective count. Quadrature encoding
determines the direction.
quadrature x1 b:
If direction is forward, rising edges on quadrature pair
signal B updates the respective count; if the direction
is backward, falling edges on quadrature pair signal B
updates the respective count. Quadrature encoding
determines the direction.
quadrature x2 a:
Any state transition on quadrature pair signal A updates
the respective count. Quadrature encoding determines the
direction.
quadrature x2 b:
Any state transition on quadrature pair signal B updates
the respective count. Quadrature encoding determines the
direction.
quadrature x4:
Any state transition on either quadrature pair signals
updates the respective count. Quadrature encoding
determines the direction.
What: /sys/bus/counter/devices/counterX/countY/name
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the device-specific name of
Count Y. If possible, this should match the name of the
respective channel as it appears in the device datasheet.
What: /sys/bus/counter/devices/counterX/countY/prescaler
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Configure the prescaler value associated with Count Y.
On the FlexTimer, the counter clock source passes through a
prescaler (i.e. a counter). This acts like a clock
divider.
What: /sys/bus/counter/devices/counterX/countY/preset
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
If the counter device supports preset registers -- registers
used to load counter channels to a set count upon device-defined
preset operation trigger events -- the preset count for channel
Y is provided by this attribute.
What: /sys/bus/counter/devices/counterX/countY/preset_enable
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Whether channel Y counter preset operation is enabled. Valid
attribute values are boolean.
What: /sys/bus/counter/devices/counterX/countY/signalZ_action
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Action mode of Count Y for Signal Z. This attribute indicates
the condition of Signal Z that triggers the count function
evaluation for Count Y. The following action modes are
available:
none:
Signal does not trigger the count function. In
Pulse-Direction count function mode, this Signal is
evaluated as Direction.
rising edge:
Low state transitions to high state.
falling edge:
High state transitions to low state.
both edges:
Any state transition.
What: /sys/bus/counter/devices/counterX/countY/num_overflows
KernelVersion: 6.1
Contact: linux-iio@vger.kernel.org
Description:
This attribute indicates the number of overflows of count Y.
What: /sys/bus/counter/devices/counterX/cascade_counts_enable_component_id
What: /sys/bus/counter/devices/counterX/external_input_phase_clock_select_component_id
What: /sys/bus/counter/devices/counterX/countY/capture_component_id
What: /sys/bus/counter/devices/counterX/countY/ceiling_component_id
What: /sys/bus/counter/devices/counterX/countY/floor_component_id
What: /sys/bus/counter/devices/counterX/countY/count_mode_component_id
What: /sys/bus/counter/devices/counterX/countY/direction_component_id
What: /sys/bus/counter/devices/counterX/countY/enable_component_id
What: /sys/bus/counter/devices/counterX/countY/error_noise_component_id
What: /sys/bus/counter/devices/counterX/countY/prescaler_component_id
What: /sys/bus/counter/devices/counterX/countY/preset_component_id
What: /sys/bus/counter/devices/counterX/countY/preset_enable_component_id
What: /sys/bus/counter/devices/counterX/countY/signalZ_action_component_id
What: /sys/bus/counter/devices/counterX/countY/num_overflows_component_id
What: /sys/bus/counter/devices/counterX/signalY/cable_fault_component_id
What: /sys/bus/counter/devices/counterX/signalY/cable_fault_enable_component_id
What: /sys/bus/counter/devices/counterX/signalY/filter_clock_prescaler_component_id
What: /sys/bus/counter/devices/counterX/signalY/index_polarity_component_id
What: /sys/bus/counter/devices/counterX/signalY/polarity_component_id
What: /sys/bus/counter/devices/counterX/signalY/synchronous_mode_component_id
What: /sys/bus/counter/devices/counterX/signalY/frequency_component_id
KernelVersion: 5.16
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the component ID of the
respective extension or Synapse.
What: /sys/bus/counter/devices/counterX/countY/spike_filter_ns
KernelVersion: 5.14
Contact: linux-iio@vger.kernel.org
Description:
If the counter device supports programmable spike filter this
attribute indicates the value in nanoseconds where noise pulses
shorter or equal to configured value are ignored. Value 0 means
filter is disabled.
What: /sys/bus/counter/devices/counterX/events_queue_size
KernelVersion: 5.16
Contact: linux-iio@vger.kernel.org
Description:
Size of the Counter events queue in number of struct
counter_event data structures. The number of elements will be
rounded-up to a power of 2.
What: /sys/bus/counter/devices/counterX/name
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the device-specific name of
the Counter. This should match the name of the device as it
appears in its respective datasheet.
What: /sys/bus/counter/devices/counterX/num_counts
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the total number of Counts
belonging to the Counter.
What: /sys/bus/counter/devices/counterX/num_signals
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the total number of Signals
belonging to the Counter.
What: /sys/bus/counter/devices/counterX/signalY/cable_fault
KernelVersion: 5.7
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates whether a differential
encoder cable fault (not connected or loose wires) is detected
for the respective channel of Signal Y. Valid attribute values
are boolean. Detection must first be enabled via the
corresponding cable_fault_enable attribute.
What: /sys/bus/counter/devices/counterX/signalY/cable_fault_enable
KernelVersion: 5.7
Contact: linux-iio@vger.kernel.org
Description:
Whether detection of differential encoder cable faults for the
respective channel of Signal Y is enabled. Valid attribute
values are boolean.
What: /sys/bus/counter/devices/counterX/signalY/filter_clock_prescaler
KernelVersion: 5.7
Contact: linux-iio@vger.kernel.org
Description:
Filter clock factor for input Signal Y. This prescaler value
affects the inputs of both quadrature pair signals.
What: /sys/bus/counter/devices/counterX/signalY/index_polarity
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Active level of index input Signal Y; irrelevant in
non-synchronous load mode.
What: /sys/bus/counter/devices/counterX/signalY/index_polarity_available
What: /sys/bus/counter/devices/counterX/signalY/synchronous_mode_available
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Discrete set of available values for the respective Signal Y
configuration are listed in this file.
What: /sys/bus/counter/devices/counterX/signalY/polarity
KernelVersion: 6.1
Contact: linux-iio@vger.kernel.org
Description:
Active level of Signal Y. The following polarity values are
available:
positive:
Signal high state considered active level (rising edge).
negative:
Signal low state considered active level (falling edge).
What: /sys/bus/counter/devices/counterX/signalY/name
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the device-specific name of
Signal Y. If possible, this should match the name of the
respective signal as it appears in the device datasheet.
What: /sys/bus/counter/devices/counterX/signalY/signal
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Signal level state of Signal Y. The following signal level
states are available:
low:
Low level state.
high:
High level state.
What: /sys/bus/counter/devices/counterX/signalY/synchronous_mode
KernelVersion: 5.2
Contact: linux-iio@vger.kernel.org
Description:
Configure the counter associated with Signal Y for
non-synchronous or synchronous load mode. Synchronous load mode
cannot be selected in non-quadrature (Pulse-Direction) clock
mode.
non-synchronous:
A logic low level is the active level at this index
input. The index function (as enabled via preset_enable)
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
preset_enable) is performed synchronously with the
quadrature clock on the active level of the index input.
What: /sys/bus/counter/devices/counterX/signalY/frequency
KernelVersion: 6.1
Contact: linux-iio@vger.kernel.org
Description:
Read-only attribute that indicates the signal Y frequency, in Hz.
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