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gpio: cdev: go back to storing debounce period in the GPIO descriptor
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This effectively reverts commits 9344e34 ("gpiolib: cdev: relocate
debounce_period_us from struct gpio_desc") and d8543cb ("gpiolib:
remove debounce_period_us from struct gpio_desc") and goes back to
storing the debounce period in microseconds in the GPIO descriptor

We're doing it in preparation for notifying the user-space about
in-kernel line config changes.

Reviewed-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20241018-gpio-notify-in-kernel-events-v5-3-c79135e58a1c@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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Bartosz Golaszewski committed Oct 22, 2024
1 parent dd26ffa commit 81625f3
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Showing 3 changed files with 43 additions and 143 deletions.
163 changes: 22 additions & 141 deletions drivers/gpio/gpiolib-cdev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,6 @@
#include <linux/overflow.h>
#include <linux/pinctrl/consumer.h>
#include <linux/poll.h>
#include <linux/rbtree.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/timekeeping.h>
Expand Down Expand Up @@ -421,7 +420,6 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)

/**
* struct line - contains the state of a requested line
* @node: to store the object in supinfo_tree if supplemental
* @desc: the GPIO descriptor for this line.
* @req: the corresponding line request
* @irq: the interrupt triggered in response to events on this GPIO
Expand All @@ -434,7 +432,6 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
* @line_seqno: the seqno for the current edge event in the sequence of
* events for this line.
* @work: the worker that implements software debouncing
* @debounce_period_us: the debounce period in microseconds
* @sw_debounced: flag indicating if the software debouncer is active
* @level: the current debounced physical level of the line
* @hdesc: the Hardware Timestamp Engine (HTE) descriptor
Expand All @@ -443,7 +440,6 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
* @last_seqno: the last sequence number before debounce period expires
*/
struct line {
struct rb_node node;
struct gpio_desc *desc;
/*
* -- edge detector specific fields --
Expand Down Expand Up @@ -477,15 +473,6 @@ struct line {
* -- debouncer specific fields --
*/
struct delayed_work work;
/*
* debounce_period_us is accessed by debounce_irq_handler() and
* process_hw_ts() which are disabled when modified by
* debounce_setup(), edge_detector_setup() or edge_detector_stop()
* or can live with a stale version when updated by
* edge_detector_update().
* The modifying functions are themselves mutually exclusive.
*/
unsigned int debounce_period_us;
/*
* sw_debounce is accessed by linereq_set_config(), which is the
* only setter, and linereq_get_values(), which can live with a
Expand Down Expand Up @@ -518,17 +505,6 @@ struct line {
#endif /* CONFIG_HTE */
};

/*
* a rbtree of the struct lines containing supplemental info.
* Used to populate gpio_v2_line_info with cdev specific fields not contained
* in the struct gpio_desc.
* A line is determined to contain supplemental information by
* line_has_supinfo().
*/
static struct rb_root supinfo_tree = RB_ROOT;
/* covers supinfo_tree */
static DEFINE_SPINLOCK(supinfo_lock);

/**
* struct linereq - contains the state of a userspace line request
* @gdev: the GPIO device the line request pertains to
Expand All @@ -542,8 +518,7 @@ static DEFINE_SPINLOCK(supinfo_lock);
* this line request. Note that this is not used when @num_lines is 1, as
* the line_seqno is then the same and is cheaper to calculate.
* @config_mutex: mutex for serializing ioctl() calls to ensure consistency
* of configuration, particularly multi-step accesses to desc flags and
* changes to supinfo status.
* of configuration, particularly multi-step accesses to desc flags.
* @lines: the lines held by this line request, with @num_lines elements.
*/
struct linereq {
Expand All @@ -559,103 +534,6 @@ struct linereq {
struct line lines[] __counted_by(num_lines);
};

static void supinfo_insert(struct line *line)
{
struct rb_node **new = &(supinfo_tree.rb_node), *parent = NULL;
struct line *entry;

guard(spinlock)(&supinfo_lock);

while (*new) {
entry = container_of(*new, struct line, node);

parent = *new;
if (line->desc < entry->desc) {
new = &((*new)->rb_left);
} else if (line->desc > entry->desc) {
new = &((*new)->rb_right);
} else {
/* this should never happen */
WARN(1, "duplicate line inserted");
return;
}
}

rb_link_node(&line->node, parent, new);
rb_insert_color(&line->node, &supinfo_tree);
}

static void supinfo_erase(struct line *line)
{
guard(spinlock)(&supinfo_lock);

rb_erase(&line->node, &supinfo_tree);
}

static struct line *supinfo_find(struct gpio_desc *desc)
{
struct rb_node *node = supinfo_tree.rb_node;
struct line *line;

while (node) {
line = container_of(node, struct line, node);
if (desc < line->desc)
node = node->rb_left;
else if (desc > line->desc)
node = node->rb_right;
else
return line;
}
return NULL;
}

static void supinfo_to_lineinfo(struct gpio_desc *desc,
struct gpio_v2_line_info *info)
{
struct gpio_v2_line_attribute *attr;
struct line *line;

guard(spinlock)(&supinfo_lock);

line = supinfo_find(desc);
if (!line)
return;

attr = &info->attrs[info->num_attrs];
attr->id = GPIO_V2_LINE_ATTR_ID_DEBOUNCE;
attr->debounce_period_us = READ_ONCE(line->debounce_period_us);
info->num_attrs++;
}

static inline bool line_has_supinfo(struct line *line)
{
return READ_ONCE(line->debounce_period_us);
}

/*
* Checks line_has_supinfo() before and after the change to avoid unnecessary
* supinfo_tree access.
* Called indirectly by linereq_create() or linereq_set_config() so line
* is already protected from concurrent changes.
*/
static void line_set_debounce_period(struct line *line,
unsigned int debounce_period_us)
{
bool was_suppl = line_has_supinfo(line);

WRITE_ONCE(line->debounce_period_us, debounce_period_us);

/* if supinfo status is unchanged then we're done */
if (line_has_supinfo(line) == was_suppl)
return;

/* supinfo status has changed, so update the tree */
if (was_suppl)
supinfo_erase(line);
else
supinfo_insert(line);
}

#define GPIO_V2_LINE_BIAS_FLAGS \
(GPIO_V2_LINE_FLAG_BIAS_PULL_UP | \
GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN | \
Expand Down Expand Up @@ -823,7 +701,7 @@ static enum hte_return process_hw_ts(struct hte_ts_data *ts, void *p)
line->total_discard_seq++;
line->last_seqno = ts->seq;
mod_delayed_work(system_wq, &line->work,
usecs_to_jiffies(READ_ONCE(line->debounce_period_us)));
usecs_to_jiffies(READ_ONCE(line->desc->debounce_period_us)));
} else {
if (unlikely(ts->seq < line->line_seqno))
return HTE_CB_HANDLED;
Expand Down Expand Up @@ -964,7 +842,7 @@ static irqreturn_t debounce_irq_handler(int irq, void *p)
struct line *line = p;

mod_delayed_work(system_wq, &line->work,
usecs_to_jiffies(READ_ONCE(line->debounce_period_us)));
usecs_to_jiffies(READ_ONCE(line->desc->debounce_period_us)));

return IRQ_HANDLED;
}
Expand Down Expand Up @@ -1047,7 +925,7 @@ static int debounce_setup(struct line *line, unsigned int debounce_period_us)
/* try hardware */
ret = gpiod_set_debounce(line->desc, debounce_period_us);
if (!ret) {
line_set_debounce_period(line, debounce_period_us);
WRITE_ONCE(line->desc->debounce_period_us, debounce_period_us);
return ret;
}
if (ret != -ENOTSUPP)
Expand Down Expand Up @@ -1132,7 +1010,8 @@ static void edge_detector_stop(struct line *line)
cancel_delayed_work_sync(&line->work);
WRITE_ONCE(line->sw_debounced, 0);
WRITE_ONCE(line->edflags, 0);
line_set_debounce_period(line, 0);
if (line->desc)
WRITE_ONCE(line->desc->debounce_period_us, 0);
/* do not change line->level - see comment in debounced_value() */
}

Expand Down Expand Up @@ -1165,7 +1044,7 @@ static int edge_detector_setup(struct line *line,
ret = debounce_setup(line, debounce_period_us);
if (ret)
return ret;
line_set_debounce_period(line, debounce_period_us);
WRITE_ONCE(line->desc->debounce_period_us, debounce_period_us);
}

/* detection disabled or sw debouncer will provide edge detection */
Expand Down Expand Up @@ -1213,12 +1092,12 @@ static int edge_detector_update(struct line *line,
gpio_v2_line_config_debounce_period(lc, line_idx);

if ((active_edflags == edflags) &&
(READ_ONCE(line->debounce_period_us) == debounce_period_us))
(READ_ONCE(line->desc->debounce_period_us) == debounce_period_us))
return 0;

/* sw debounced and still will be...*/
if (debounce_period_us && READ_ONCE(line->sw_debounced)) {
line_set_debounce_period(line, debounce_period_us);
WRITE_ONCE(line->desc->debounce_period_us, debounce_period_us);
/*
* ensure event fifo is initialised if edge detection
* is now enabled.
Expand Down Expand Up @@ -1677,22 +1556,17 @@ static ssize_t linereq_read(struct file *file, char __user *buf,

static void linereq_free(struct linereq *lr)
{
struct line *line;
unsigned int i;

if (lr->device_unregistered_nb.notifier_call)
blocking_notifier_chain_unregister(&lr->gdev->device_notifier,
&lr->device_unregistered_nb);

for (i = 0; i < lr->num_lines; i++) {
line = &lr->lines[i];
if (!line->desc)
continue;

edge_detector_stop(line);
if (line_has_supinfo(line))
supinfo_erase(line);
gpiod_free(line->desc);
if (lr->lines[i].desc) {
edge_detector_stop(&lr->lines[i]);
gpiod_free(lr->lines[i].desc);
}
}
kfifo_free(&lr->events);
kfree(lr->label);
Expand Down Expand Up @@ -2363,6 +2237,7 @@ static void gpio_v2_line_info_changed_to_v1(
static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
struct gpio_v2_line_info *info)
{
u32 debounce_period_us;
unsigned long dflags;
const char *label;

Expand Down Expand Up @@ -2435,6 +2310,14 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME;
else if (test_bit(FLAG_EVENT_CLOCK_HTE, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE;

debounce_period_us = READ_ONCE(desc->debounce_period_us);
if (debounce_period_us) {
info->attrs[info->num_attrs].id = GPIO_V2_LINE_ATTR_ID_DEBOUNCE;
info->attrs[info->num_attrs].debounce_period_us =
debounce_period_us;
info->num_attrs++;
}
}

struct gpio_chardev_data {
Expand Down Expand Up @@ -2540,7 +2423,6 @@ static int lineinfo_get(struct gpio_chardev_data *cdev, void __user *ip,
return -EBUSY;
}
gpio_desc_to_lineinfo(desc, &lineinfo);
supinfo_to_lineinfo(desc, &lineinfo);

if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) {
if (watch)
Expand Down Expand Up @@ -2633,7 +2515,6 @@ static int lineinfo_changed_notify(struct notifier_block *nb,
chg.event_type = action;
chg.timestamp_ns = ktime_get_ns();
gpio_desc_to_lineinfo(desc, &chg.info);
supinfo_to_lineinfo(desc, &chg.info);

ret = kfifo_in_spinlocked(&cdev->events, &chg, 1, &cdev->wait.lock);
if (ret)
Expand Down
18 changes: 16 additions & 2 deletions drivers/gpio/gpiolib.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2432,7 +2432,9 @@ static void gpiod_free_commit(struct gpio_desc *desc)
#endif
desc_set_label(desc, NULL);
WRITE_ONCE(desc->flags, flags);

#ifdef CONFIG_GPIO_CDEV
WRITE_ONCE(desc->debounce_period_us, 0);
#endif
gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_RELEASED);
}
}
Expand Down Expand Up @@ -2564,14 +2566,26 @@ EXPORT_SYMBOL_GPL(gpiochip_free_own_desc);

static int gpio_do_set_config(struct gpio_desc *desc, unsigned long config)
{
int ret;

CLASS(gpio_chip_guard, guard)(desc);
if (!guard.gc)
return -ENODEV;

if (!guard.gc->set_config)
return -ENOTSUPP;

return guard.gc->set_config(guard.gc, gpio_chip_hwgpio(desc), config);
ret = guard.gc->set_config(guard.gc, gpio_chip_hwgpio(desc), config);
#ifdef CONFIG_GPIO_CDEV
/*
* Special case - if we're setting debounce period, we need to store
* it in the descriptor in case user-space wants to know it.
*/
if (!ret && pinconf_to_config_param(config) == PIN_CONFIG_INPUT_DEBOUNCE)
WRITE_ONCE(desc->debounce_period_us,
pinconf_to_config_argument(config));
#endif
return ret;
}

static int gpio_set_config_with_argument(struct gpio_desc *desc,
Expand Down
5 changes: 5 additions & 0 deletions drivers/gpio/gpiolib.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,7 @@ struct gpio_desc_label {
* @label: Name of the consumer
* @name: Line name
* @hog: Pointer to the device node that hogs this line (if any)
* @debounce_period_us: Debounce period in microseconds
*
* These are obtained using gpiod_get() and are preferable to the old
* integer-based handles.
Expand Down Expand Up @@ -202,6 +203,10 @@ struct gpio_desc {
#ifdef CONFIG_OF_DYNAMIC
struct device_node *hog;
#endif
#ifdef CONFIG_GPIO_CDEV
/* debounce period in microseconds */
unsigned int debounce_period_us;
#endif
};

#define gpiod_not_found(desc) (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT)
Expand Down

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