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counter: i8254: Introduce the Intel 8254 interface library module

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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>
This commit is contained in:
William Breathitt Gray 2023-04-16 13:36:53 -04:00
parent 98ffe02529
commit d428487471
8 changed files with 558 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
Documentation/ABI/testing/sysfs-bus-counter
View File

@ -90,6 +90,60 @@ Description:
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

7
MAINTAINERS
View File

@ -10257,6 +10257,13 @@ L: linux-fbdev@vger.kernel.org
S: Maintained
F: drivers/video/fbdev/i810/
INTEL 8254 COUNTER DRIVER
M: William Breathitt Gray <william.gray@linaro.org>
L: linux-iio@vger.kernel.org
S: Maintained
F: drivers/counter/i8254.c
F: include/linux/i8254.h
INTEL 8255 GPIO DRIVER
M: William Breathitt Gray <william.gray@linaro.org>
L: linux-gpio@vger.kernel.org

15
drivers/counter/Kconfig
View File

@ -10,6 +10,21 @@ menuconfig COUNTER
interface. You only need to enable this, if you also want to enable
one or more of the counter device drivers below.
config I8254
tristate
select COUNTER
select REGMAP
help
Enables support for the i8254 interface library functions. The i8254
interface library provides functions to facilitate communication with
interfaces compatible with the venerable Intel 8254 Programmable
Interval Timer (PIT). The Intel 825x family of chips was first
released in the early 1980s but compatible interfaces are nowadays
typically found embedded in larger VLSI processing chips and FPGA
components.
If built as a module its name will be i8254.
if COUNTER
config 104_QUAD_8

1
drivers/counter/Makefile
View File

@ -6,6 +6,7 @@
obj-$(CONFIG_COUNTER) += counter.o
counter-y := counter-core.o counter-sysfs.o counter-chrdev.o
obj-$(CONFIG_I8254) += i8254.o
obj-$(CONFIG_104_QUAD_8) += 104-quad-8.o
obj-$(CONFIG_INTERRUPT_CNT) += interrupt-cnt.o
obj-$(CONFIG_RZ_MTU3_CNT) += rz-mtu3-cnt.o

8
drivers/counter/counter-sysfs.c
View File

@ -88,7 +88,13 @@ static const char *const counter_count_mode_str[] = {
[COUNTER_COUNT_MODE_NORMAL] = "normal",
[COUNTER_COUNT_MODE_RANGE_LIMIT] = "range limit",
[COUNTER_COUNT_MODE_NON_RECYCLE] = "non-recycle",
[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n"
[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n",
[COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT] = "interrupt on terminal count",
[COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT] = "hardware retriggerable one-shot",
[COUNTER_COUNT_MODE_RATE_GENERATOR] = "rate generator",
[COUNTER_COUNT_MODE_SQUARE_WAVE_MODE] = "square wave mode",
[COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE] = "software triggered strobe",
[COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE] = "hardware triggered strobe",
};
static const char *const counter_signal_polarity_str[] = {

447
drivers/counter/i8254.c Normal file
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@ -0,0 +1,447 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Intel 8254 Programmable Interval Timer
* Copyright (C) William Breathitt Gray
*/
#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/counter.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/i8254.h>
#include <linux/limits.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/regmap.h>
#include <asm/unaligned.h>
#define I8254_COUNTER_REG(_counter) (_counter)
#define I8254_CONTROL_REG 0x3
#define I8254_SC GENMASK(7, 6)
#define I8254_RW GENMASK(5, 4)
#define I8254_M GENMASK(3, 1)
#define I8254_CONTROL(_sc, _rw, _m) \
(u8_encode_bits(_sc, I8254_SC) | u8_encode_bits(_rw, I8254_RW) | \
u8_encode_bits(_m, I8254_M))
#define I8254_RW_TWO_BYTE 0x3
#define I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT 0
#define I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT 1
#define I8254_MODE_RATE_GENERATOR 2
#define I8254_MODE_SQUARE_WAVE_MODE 3
#define I8254_MODE_SOFTWARE_TRIGGERED_STROBE 4
#define I8254_MODE_HARDWARE_TRIGGERED_STROBE 5
#define I8254_COUNTER_LATCH(_counter) I8254_CONTROL(_counter, 0x0, 0x0)
#define I8254_PROGRAM_COUNTER(_counter, _mode) I8254_CONTROL(_counter, I8254_RW_TWO_BYTE, _mode)
#define I8254_NUM_COUNTERS 3
/**
* struct i8254 - I8254 device private data structure
* @lock: synchronization lock to prevent I/O race conditions
* @preset: array of Counter Register states
* @out_mode: array of mode configuration states
* @map: Regmap for the device
*/
struct i8254 {
struct mutex lock;
u16 preset[I8254_NUM_COUNTERS];
u8 out_mode[I8254_NUM_COUNTERS];
struct regmap *map;
};
static int i8254_count_read(struct counter_device *const counter, struct counter_count *const count,
u64 *const val)
{
struct i8254 *const priv = counter_priv(counter);
int ret;
u8 value[2];
mutex_lock(&priv->lock);
ret = regmap_write(priv->map, I8254_CONTROL_REG, I8254_COUNTER_LATCH(count->id));
if (ret) {
mutex_unlock(&priv->lock);
return ret;
}
ret = regmap_noinc_read(priv->map, I8254_COUNTER_REG(count->id), value, sizeof(value));
if (ret) {
mutex_unlock(&priv->lock);
return ret;
}
mutex_unlock(&priv->lock);
*val = get_unaligned_le16(value);
return ret;
}
static int i8254_function_read(struct counter_device *const counter,
struct counter_count *const count,
enum counter_function *const function)
{
*function = COUNTER_FUNCTION_DECREASE;
return 0;
}
#define I8254_SYNAPSES_PER_COUNT 2
#define I8254_SIGNAL_ID_CLK 0
#define I8254_SIGNAL_ID_GATE 1
static int i8254_action_read(struct counter_device *const counter,
struct counter_count *const count,
struct counter_synapse *const synapse,
enum counter_synapse_action *const action)
{
struct i8254 *const priv = counter_priv(counter);
switch (synapse->signal->id % I8254_SYNAPSES_PER_COUNT) {
case I8254_SIGNAL_ID_CLK:
*action = COUNTER_SYNAPSE_ACTION_FALLING_EDGE;
return 0;
case I8254_SIGNAL_ID_GATE:
switch (priv->out_mode[count->id]) {
case I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
case I8254_MODE_RATE_GENERATOR:
case I8254_MODE_SQUARE_WAVE_MODE:
case I8254_MODE_HARDWARE_TRIGGERED_STROBE:
*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
return 0;
default:
*action = COUNTER_SYNAPSE_ACTION_NONE;
return 0;
}
default:
/* should never reach this path */
return -EINVAL;
}
}
static int i8254_count_ceiling_read(struct counter_device *const counter,
struct counter_count *const count, u64 *const ceiling)
{
struct i8254 *const priv = counter_priv(counter);
mutex_lock(&priv->lock);
switch (priv->out_mode[count->id]) {
case I8254_MODE_RATE_GENERATOR:
/* Rate Generator decrements 0 by one and the counter "wraps around" */
*ceiling = (priv->preset[count->id] == 0) ? U16_MAX : priv->preset[count->id];
break;
case I8254_MODE_SQUARE_WAVE_MODE:
if (priv->preset[count->id] % 2)
*ceiling = priv->preset[count->id] - 1;
else if (priv->preset[count->id] == 0)
/* Square Wave Mode decrements 0 by two and the counter "wraps around" */
*ceiling = U16_MAX - 1;
else
*ceiling = priv->preset[count->id];
break;
default:
*ceiling = U16_MAX;
break;
}
mutex_unlock(&priv->lock);
return 0;
}
static int i8254_count_mode_read(struct counter_device *const counter,
struct counter_count *const count,
enum counter_count_mode *const count_mode)
{
const struct i8254 *const priv = counter_priv(counter);
switch (priv->out_mode[count->id]) {
case I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT:
*count_mode = COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT;
return 0;
case I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
*count_mode = COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT;
return 0;
case I8254_MODE_RATE_GENERATOR:
*count_mode = COUNTER_COUNT_MODE_RATE_GENERATOR;
return 0;
case I8254_MODE_SQUARE_WAVE_MODE:
*count_mode = COUNTER_COUNT_MODE_SQUARE_WAVE_MODE;
return 0;
case I8254_MODE_SOFTWARE_TRIGGERED_STROBE:
*count_mode = COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE;
return 0;
case I8254_MODE_HARDWARE_TRIGGERED_STROBE:
*count_mode = COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE;
return 0;
default:
/* should never reach this path */
return -EINVAL;
}
}
static int i8254_count_mode_write(struct counter_device *const counter,
struct counter_count *const count,
const enum counter_count_mode count_mode)
{
struct i8254 *const priv = counter_priv(counter);
u8 out_mode;
int ret;
switch (count_mode) {
case COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT:
out_mode = I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT;
break;
case COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT:
out_mode = I8254_MODE_HARDWARE_RETRIGGERABLE_ONESHOT;
break;
case COUNTER_COUNT_MODE_RATE_GENERATOR:
out_mode = I8254_MODE_RATE_GENERATOR;
break;
case COUNTER_COUNT_MODE_SQUARE_WAVE_MODE:
out_mode = I8254_MODE_SQUARE_WAVE_MODE;
break;
case COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE:
out_mode = I8254_MODE_SOFTWARE_TRIGGERED_STROBE;
break;
case COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE:
out_mode = I8254_MODE_HARDWARE_TRIGGERED_STROBE;
break;
default:
/* should never reach this path */
return -EINVAL;
}
mutex_lock(&priv->lock);
/* Counter Register is cleared when the counter is programmed */
priv->preset[count->id] = 0;
priv->out_mode[count->id] = out_mode;
ret = regmap_write(priv->map, I8254_CONTROL_REG,
I8254_PROGRAM_COUNTER(count->id, out_mode));
mutex_unlock(&priv->lock);
return ret;
}
static int i8254_count_floor_read(struct counter_device *const counter,
struct counter_count *const count, u64 *const floor)
{
struct i8254 *const priv = counter_priv(counter);
mutex_lock(&priv->lock);
switch (priv->out_mode[count->id]) {
case I8254_MODE_RATE_GENERATOR:
/* counter is always reloaded after 1, but 0 is a possible reload value */
*floor = (priv->preset[count->id] == 0) ? 0 : 1;
break;
case I8254_MODE_SQUARE_WAVE_MODE:
/* counter is always reloaded after 2 for even preset values */
*floor = (priv->preset[count->id] % 2 || priv->preset[count->id] == 0) ? 0 : 2;
break;
default:
*floor = 0;
break;
}
mutex_unlock(&priv->lock);
return 0;
}
static int i8254_count_preset_read(struct counter_device *const counter,
struct counter_count *const count, u64 *const preset)
{
const struct i8254 *const priv = counter_priv(counter);
*preset = priv->preset[count->id];
return 0;
}
static int i8254_count_preset_write(struct counter_device *const counter,
struct counter_count *const count, const u64 preset)
{
struct i8254 *const priv = counter_priv(counter);
int ret;
u8 value[2];
if (preset > U16_MAX)
return -ERANGE;
mutex_lock(&priv->lock);
if (priv->out_mode[count->id] == I8254_MODE_RATE_GENERATOR ||
priv->out_mode[count->id] == I8254_MODE_SQUARE_WAVE_MODE) {
if (preset == 1) {
mutex_unlock(&priv->lock);
return -EINVAL;
}
}
priv->preset[count->id] = preset;
put_unaligned_le16(preset, value);
ret = regmap_noinc_write(priv->map, I8254_COUNTER_REG(count->id), value, 2);
mutex_unlock(&priv->lock);
return ret;
}
static int i8254_init_hw(struct regmap *const map)
{
unsigned long i;
int ret;
for (i = 0; i < I8254_NUM_COUNTERS; i++) {
/* Initialize each counter to Mode 0 */
ret = regmap_write(map, I8254_CONTROL_REG,
I8254_PROGRAM_COUNTER(i, I8254_MODE_INTERRUPT_ON_TERMINAL_COUNT));
if (ret)
return ret;
}
return 0;
}
static const struct counter_ops i8254_ops = {
.count_read = i8254_count_read,
.function_read = i8254_function_read,
.action_read = i8254_action_read,
};
#define I8254_SIGNAL(_id, _name) { \
.id = (_id), \
.name = (_name), \
}
static struct counter_signal i8254_signals[] = {
I8254_SIGNAL(0, "CLK 0"), I8254_SIGNAL(1, "GATE 0"),
I8254_SIGNAL(2, "CLK 1"), I8254_SIGNAL(3, "GATE 1"),
I8254_SIGNAL(4, "CLK 2"), I8254_SIGNAL(5, "GATE 2"),
};
static const enum counter_synapse_action i8254_clk_actions[] = {
COUNTER_SYNAPSE_ACTION_FALLING_EDGE,
};
static const enum counter_synapse_action i8254_gate_actions[] = {
COUNTER_SYNAPSE_ACTION_NONE,
COUNTER_SYNAPSE_ACTION_RISING_EDGE,
};
#define I8254_SYNAPSES_BASE(_id) ((_id) * I8254_SYNAPSES_PER_COUNT)
#define I8254_SYNAPSE_CLK(_id) { \
.actions_list = i8254_clk_actions, \
.num_actions = ARRAY_SIZE(i8254_clk_actions), \
.signal = &i8254_signals[I8254_SYNAPSES_BASE(_id) + 0], \
}
#define I8254_SYNAPSE_GATE(_id) { \
.actions_list = i8254_gate_actions, \
.num_actions = ARRAY_SIZE(i8254_gate_actions), \
.signal = &i8254_signals[I8254_SYNAPSES_BASE(_id) + 1], \
}
static struct counter_synapse i8254_synapses[] = {
I8254_SYNAPSE_CLK(0), I8254_SYNAPSE_GATE(0),
I8254_SYNAPSE_CLK(1), I8254_SYNAPSE_GATE(1),
I8254_SYNAPSE_CLK(2), I8254_SYNAPSE_GATE(2),
};
static const enum counter_function i8254_functions_list[] = {
COUNTER_FUNCTION_DECREASE,
};
static const enum counter_count_mode i8254_count_modes[] = {
COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT,
COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT,
COUNTER_COUNT_MODE_RATE_GENERATOR,
COUNTER_COUNT_MODE_SQUARE_WAVE_MODE,
COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE,
COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE,
};
static DEFINE_COUNTER_AVAILABLE(i8254_count_modes_available, i8254_count_modes);
static struct counter_comp i8254_count_ext[] = {
COUNTER_COMP_CEILING(i8254_count_ceiling_read, NULL),
COUNTER_COMP_COUNT_MODE(i8254_count_mode_read, i8254_count_mode_write,
i8254_count_modes_available),
COUNTER_COMP_FLOOR(i8254_count_floor_read, NULL),
COUNTER_COMP_PRESET(i8254_count_preset_read, i8254_count_preset_write),
};
#define I8254_COUNT(_id, _name) { \
.id = (_id), \
.name = (_name), \
.functions_list = i8254_functions_list, \
.num_functions = ARRAY_SIZE(i8254_functions_list), \
.synapses = &i8254_synapses[I8254_SYNAPSES_BASE(_id)], \
.num_synapses = I8254_SYNAPSES_PER_COUNT, \
.ext = i8254_count_ext, \
.num_ext = ARRAY_SIZE(i8254_count_ext) \
}
static struct counter_count i8254_counts[I8254_NUM_COUNTERS] = {
I8254_COUNT(0, "Counter 0"), I8254_COUNT(1, "Counter 1"), I8254_COUNT(2, "Counter 2"),
};
/**
* devm_i8254_regmap_register - Register an i8254 Counter device
* @dev: device that is registering this i8254 Counter device
* @config: configuration for i8254_regmap_config
*
* Registers an Intel 8254 Programmable Interval Timer Counter device. Returns 0 on success and
* negative error number on failure.
*/
int devm_i8254_regmap_register(struct device *const dev,
const struct i8254_regmap_config *const config)
{
struct counter_device *counter;
struct i8254 *priv;
int err;
if (!config->parent)
return -EINVAL;
if (!config->map)
return -EINVAL;
counter = devm_counter_alloc(dev, sizeof(*priv));
if (!counter)
return -ENOMEM;
priv = counter_priv(counter);
priv->map = config->map;
counter->name = dev_name(config->parent);
counter->parent = config->parent;
counter->ops = &i8254_ops;
counter->counts = i8254_counts;
counter->num_counts = ARRAY_SIZE(i8254_counts);
counter->signals = i8254_signals;
counter->num_signals = ARRAY_SIZE(i8254_signals);
mutex_init(&priv->lock);
err = i8254_init_hw(priv->map);
if (err)
return err;
err = devm_counter_add(dev, counter);
if (err < 0)
return dev_err_probe(dev, err, "Failed to add counter\n");
return 0;
}
EXPORT_SYMBOL_NS_GPL(devm_i8254_regmap_register, I8254);
MODULE_AUTHOR("William Breathitt Gray");
MODULE_DESCRIPTION("Intel 8254 Programmable Interval Timer");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(COUNTER);

21
include/linux/i8254.h Normal file
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@ -0,0 +1,21 @@
/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (C) William Breathitt Gray */
#ifndef _I8254_H_
#define _I8254_H_
struct device;
struct regmap;
/**
* struct i8254_regmap_config - Configuration for the register map of an i8254
* @parent: parent device
* @map: regmap for the i8254
*/
struct i8254_regmap_config {
struct device *parent;
struct regmap *map;
};
int devm_i8254_regmap_register(struct device *dev, const struct i8254_regmap_config *config);
#endif /* _I8254_H_ */

6
include/uapi/linux/counter.h
View File

@ -127,6 +127,12 @@ enum counter_count_mode {
COUNTER_COUNT_MODE_RANGE_LIMIT,
COUNTER_COUNT_MODE_NON_RECYCLE,
COUNTER_COUNT_MODE_MODULO_N,
COUNTER_COUNT_MODE_INTERRUPT_ON_TERMINAL_COUNT,
COUNTER_COUNT_MODE_HARDWARE_RETRIGGERABLE_ONESHOT,
COUNTER_COUNT_MODE_RATE_GENERATOR,
COUNTER_COUNT_MODE_SQUARE_WAVE_MODE,
COUNTER_COUNT_MODE_SOFTWARE_TRIGGERED_STROBE,
COUNTER_COUNT_MODE_HARDWARE_TRIGGERED_STROBE,
};
/* Count function values */