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Date: Wed, 20 Nov 2019 15:34:09 +0200
From: Peter Ujfalusi <peter.ujfalusi@...com>
To: <linus.walleij@...aro.org>, <bgolaszewski@...libre.com>,
<robh+dt@...nel.org>
CC: <linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<m.szyprowski@...sung.com>, <broonie@...nel.org>,
<mripard@...nel.org>, <p.zabel@...gutronix.de>,
<devicetree@...r.kernel.org>
Subject: [RFC 2/2] gpiolib: Support for (output only) shared GPIO line
This patch adds basic support for handling shared GPIO lines in the core.
The line must be configured with a child node in DT.
Based on the configuration the core will use different strategy to manage
the shared line:
refcounted low: Keep the line low as long as there is at least one low
request is registered
refcounted high: Keep the line high as long as there is at least one high
request is registered
pass through: all requests are allowed to go through without refcounting.
The pass through mode is equivalent to how currently the
GPIOD_FLAGS_BIT_NONEXCLUSIVE is handled.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
---
drivers/gpio/gpiolib-of.c | 28 ++++++--
drivers/gpio/gpiolib.c | 132 +++++++++++++++++++++++++++++++++++---
drivers/gpio/gpiolib.h | 10 +++
3 files changed, 157 insertions(+), 13 deletions(-)
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index bd06743a5d7c..fbb628e6d8bc 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -531,6 +531,7 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
* @lflags: bitmask of gpio_lookup_flags GPIO_* values - returned from
* of_find_gpio() or of_parse_own_gpio()
* @dflags: gpiod_flags - optional GPIO initialization flags
+ * @sflags: Extra flags for the shared GPIO usage
*
* Returns GPIO descriptor to use with Linux GPIO API, or one of the errno
* value on the error condition.
@@ -539,7 +540,8 @@ static struct gpio_desc *of_parse_own_gpio(struct device_node *np,
struct gpio_chip *chip,
unsigned int idx, const char **name,
unsigned long *lflags,
- enum gpiod_flags *dflags)
+ enum gpiod_flags *dflags,
+ unsigned long *sflags)
{
struct device_node *chip_np;
enum of_gpio_flags xlate_flags;
@@ -592,6 +594,15 @@ static struct gpio_desc *of_parse_own_gpio(struct device_node *np,
return ERR_PTR(-EINVAL);
}
+ if (sflags) {
+ *sflags = 0;
+
+ if (of_property_read_bool(np, "refcounted-low"))
+ set_bit(FLAG_REFCOUNT_LOW, sflags);
+ else if (of_property_read_bool(np, "refcounted-high"))
+ set_bit(FLAG_REFCOUNT_HIGH, sflags);
+ }
+
if (name && of_property_read_string(np, "line-name", name))
*name = np->name;
@@ -611,22 +622,29 @@ static int of_gpiochip_scan_gpios(struct gpio_chip *chip)
struct gpio_desc *desc = NULL;
struct device_node *np;
const char *name;
- unsigned long lflags;
+ unsigned long lflags, sflags;
enum gpiod_flags dflags;
unsigned int i;
int ret;
for_each_available_child_of_node(chip->of_node, np) {
- if (!of_property_read_bool(np, "gpio-hog"))
+ bool is_hog = of_property_read_bool(np, "gpio-hog");
+ bool is_shared = of_property_read_bool(np, "gpio-shared");
+ if (!is_hog && !is_shared)
continue;
for (i = 0;; i++) {
desc = of_parse_own_gpio(np, chip, i, &name, &lflags,
- &dflags);
+ &dflags,
+ is_shared ? &sflags : NULL);
if (IS_ERR(desc))
break;
- ret = gpiod_hog(desc, name, lflags, dflags);
+ if (is_hog)
+ ret = gpiod_hog(desc, name, lflags, dflags);
+ if (is_shared)
+ ret = gpiod_share(desc, name, lflags, dflags,
+ sflags);
if (ret < 0) {
of_node_put(np);
return ret;
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index dba5f08f308c..b01836cd9e58 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -81,7 +81,7 @@ LIST_HEAD(gpio_devices);
static DEFINE_MUTEX(gpio_machine_hogs_mutex);
static LIST_HEAD(gpio_machine_hogs);
-static void gpiochip_free_hogs(struct gpio_chip *chip);
+static void gpiochip_free_owns(struct gpio_chip *chip);
static int gpiochip_add_irqchip(struct gpio_chip *gpiochip,
struct lock_class_key *lock_key,
struct lock_class_key *request_key);
@@ -1558,7 +1558,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
err_remove_acpi_chip:
acpi_gpiochip_remove(chip);
err_remove_of_chip:
- gpiochip_free_hogs(chip);
+ gpiochip_free_owns(chip);
of_gpiochip_remove(chip);
err_free_gpiochip_mask:
gpiochip_remove_pin_ranges(chip);
@@ -1612,7 +1612,7 @@ void gpiochip_remove(struct gpio_chip *chip)
/* FIXME: should the legacy sysfs handling be moved to gpio_device? */
gpiochip_sysfs_unregister(gdev);
- gpiochip_free_hogs(chip);
+ gpiochip_free_owns(chip);
/* Numb the device, cancelling all outstanding operations */
gdev->chip = NULL;
gpiochip_irqchip_remove(chip);
@@ -2788,6 +2788,13 @@ static int gpiod_request_commit(struct gpio_desc *desc, const char *label)
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
desc_set_label(desc, label ? : "?");
ret = 0;
+ } else if (test_bit(FLAG_IS_SHARED, &desc->flags)) {
+ desc->shared_users++;
+ pr_info("New user for shared GPIO line %d\n",
+ desc_to_gpio(desc));
+ kfree_const(label);
+ ret = 0;
+ goto done;
} else {
kfree_const(label);
ret = -EBUSY;
@@ -2894,6 +2901,15 @@ static bool gpiod_free_commit(struct gpio_desc *desc)
spin_lock_irqsave(&gpio_lock, flags);
+ if (test_bit(FLAG_IS_SHARED, &desc->flags) && desc->shared_users) {
+ if (--desc->shared_users) {
+ spin_unlock_irqrestore(&gpio_lock, flags);
+ pr_info("User dropped for shared GPIO line %d\n",
+ desc_to_gpio(desc));
+ return true;
+ }
+ }
+
chip = desc->gdev->chip;
if (chip && test_bit(FLAG_REQUESTED, &desc->flags)) {
if (chip->free) {
@@ -3126,10 +3142,44 @@ int gpiod_direction_input(struct gpio_desc *desc)
}
EXPORT_SYMBOL_GPL(gpiod_direction_input);
+static int gpiod_get_refcounted_value(struct gpio_desc *desc, int value)
+{
+ value = !!value;
+
+ if (!test_bit(FLAG_IS_SHARED, &desc->flags))
+ return value;
+
+ if (test_bit(FLAG_REFCOUNT_LOW, &desc->flags)) {
+ if (!value)
+ desc->level_refcount++;
+ else if (desc->level_refcount)
+ desc->level_refcount--;
+
+ if (desc->level_refcount)
+ value = 0;
+ } else if (test_bit(FLAG_REFCOUNT_HIGH, &desc->flags)) {
+ if (value)
+ desc->level_refcount++;
+ else if (desc->level_refcount)
+ desc->level_refcount--;
+
+ if (desc->level_refcount)
+ value = 1;
+ }
+
+ pr_debug("Shared %s GPIO line %d: counter: %d: value: %d\n",
+ test_bit(FLAG_REFCOUNT_LOW, &desc->flags) ? "refcounted low" :
+ test_bit(FLAG_REFCOUNT_HIGH, &desc->flags) ? "refcounted high" :
+ "pass through", desc_to_gpio(desc), desc->level_refcount,
+ value);
+
+ return value;
+}
+
static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
{
struct gpio_chip *gc = desc->gdev->chip;
- int val = !!value;
+ int val;
int ret = 0;
/*
@@ -3144,6 +3194,8 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
return -EIO;
}
+ val = gpiod_get_refcounted_value(desc, value);
+
if (gc->direction_output) {
ret = gc->direction_output(gc, gpio_chip_hwgpio(desc), val);
} else {
@@ -3665,6 +3717,7 @@ static void gpiod_set_raw_value_commit(struct gpio_desc *desc, bool value)
struct gpio_chip *chip;
chip = desc->gdev->chip;
+ value = gpiod_get_refcounted_value(desc, value);
trace_gpio_value(desc_to_gpio(desc), 0, value);
chip->set(chip, gpio_chip_hwgpio(desc), value);
}
@@ -4618,6 +4671,9 @@ int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
{
int ret;
+ if (test_bit(FLAG_IS_SHARED, &desc->flags))
+ goto out;
+
if (lflags & GPIO_ACTIVE_LOW)
set_bit(FLAG_ACTIVE_LOW, &desc->flags);
@@ -4659,6 +4715,7 @@ int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
return 0;
}
+out:
/* Process flags */
if (dflags & GPIOD_FLAGS_BIT_DIR_OUT)
ret = gpiod_direction_output(desc,
@@ -4890,16 +4947,72 @@ int gpiod_hog(struct gpio_desc *desc, const char *name,
}
/**
- * gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
+ * gpiod_share - Share the specified GPIO desc given the provided flags
+ * @desc: gpio whose value will be assigned
+ * @name: gpio line name
+ * @lflags: bitmask of gpio_lookup_flags GPIO_* values - returned from
+ * of_find_gpio() or of_get_gpio_hog()
+ * @dflags: gpiod_flags - optional GPIO initialization flags
+ * @sflags: Extra flags for the shared GPIO usage
+ */
+int gpiod_share(struct gpio_desc *desc, const char *name,
+ unsigned long lflags, enum gpiod_flags dflags,
+ unsigned long sflags)
+{
+ struct gpio_chip *chip;
+ struct gpio_desc *local_desc;
+ int hwnum;
+ int ret;
+
+ chip = gpiod_to_chip(desc);
+ hwnum = gpio_chip_hwgpio(desc);
+
+ if (!(dflags & GPIOD_FLAGS_BIT_DIR_OUT)) {
+ pr_err("shared GPIO %s (chip %s, offset %d) must be output\n",
+ name, chip->label, hwnum);
+ return -EINVAL;
+ }
+
+ local_desc = gpiochip_request_own_desc(chip, hwnum, name,
+ lflags, dflags);
+ if (IS_ERR(local_desc)) {
+ ret = PTR_ERR(local_desc);
+ pr_err("requesting shared GPIO %s (chip %s, offset %d) failed, %d\n",
+ name, chip->label, hwnum, ret);
+ return ret;
+ }
+
+ /* Mark GPIO as shared and set refcounting level if not pass through */
+ set_bit(FLAG_IS_SHARED, &desc->flags);
+ if (test_bit(FLAG_REFCOUNT_LOW, &sflags))
+ set_bit(FLAG_REFCOUNT_LOW, &desc->flags);
+ else if (test_bit(FLAG_REFCOUNT_HIGH, &sflags))
+ set_bit(FLAG_REFCOUNT_HIGH, &desc->flags);
+
+ pr_info("GPIO line %d (%s) shared as %s\n",
+ desc_to_gpio(desc), name,
+ test_bit(FLAG_REFCOUNT_LOW, &desc->flags) ? "refcounted low" :
+ test_bit(FLAG_REFCOUNT_HIGH, &desc->flags) ? "refcounted high" :
+ "pass through");
+
+ return 0;
+}
+
+/**
+ * gpiochip_free_owns - Scan gpio-controller chip and release hogged or shared
+ * GPIOs
* @chip: gpio chip to act on
*/
-static void gpiochip_free_hogs(struct gpio_chip *chip)
+static void gpiochip_free_owns(struct gpio_chip *chip)
{
int id;
for (id = 0; id < chip->ngpio; id++) {
if (test_bit(FLAG_IS_HOGGED, &chip->gpiodev->descs[id].flags))
gpiochip_free_own_desc(&chip->gpiodev->descs[id]);
+
+ if (test_bit(FLAG_IS_SHARED, &chip->gpiodev->descs[id].flags))
+ gpiochip_free_own_desc(&chip->gpiodev->descs[id]);
}
}
@@ -5115,6 +5228,7 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
bool is_out;
bool is_irq;
bool active_low;
+ bool shared;
for (i = 0; i < gdev->ngpio; i++, gpio++, gdesc++) {
if (!test_bit(FLAG_REQUESTED, &gdesc->flags)) {
@@ -5129,12 +5243,14 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
is_irq = test_bit(FLAG_USED_AS_IRQ, &gdesc->flags);
active_low = test_bit(FLAG_ACTIVE_LOW, &gdesc->flags);
- seq_printf(s, " gpio-%-3d (%-20.20s|%-20.20s) %s %s %s%s",
+ shared = test_bit(FLAG_IS_SHARED, &gdesc->flags);
+ seq_printf(s, " gpio-%-3d (%-20.20s|%-20.20s) %s %s %s%s%s",
gpio, gdesc->name ? gdesc->name : "", gdesc->label,
is_out ? "out" : "in ",
chip->get ? (chip->get(chip, i) ? "hi" : "lo") : "? ",
is_irq ? "IRQ " : "",
- active_low ? "ACTIVE LOW" : "");
+ active_low ? "ACTIVE LOW " : "",
+ shared ? "SHARED" : "");
seq_printf(s, "\n");
}
}
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index ca9bc1e4803c..0eec0857e3a8 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -111,11 +111,18 @@ struct gpio_desc {
#define FLAG_PULL_UP 13 /* GPIO has pull up enabled */
#define FLAG_PULL_DOWN 14 /* GPIO has pull down enabled */
#define FLAG_BIAS_DISABLE 15 /* GPIO has pull disabled */
+#define FLAG_IS_SHARED 16 /* GPIO is shared */
+#define FLAG_REFCOUNT_LOW 17 /* Shared GPIO is refcounted for raw low */
+#define FLAG_REFCOUNT_HIGH 18 /* Shared GPIO is refcounted for raw high */
/* Connection label */
const char *label;
/* Name of the GPIO */
const char *name;
+ /* Number of users of a shared GPIO */
+ int shared_users;
+ /* Reference counter for shared GPIO (low or high level) */
+ int level_refcount;
};
int gpiod_request(struct gpio_desc *desc, const char *label);
@@ -124,6 +131,9 @@ int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
unsigned long lflags, enum gpiod_flags dflags);
int gpiod_hog(struct gpio_desc *desc, const char *name,
unsigned long lflags, enum gpiod_flags dflags);
+int gpiod_share(struct gpio_desc *desc, const char *name,
+ unsigned long lflags, enum gpiod_flags dflags,
+ unsigned long sflags);
/*
* Return the GPIO number of the passed descriptor relative to its chip
--
Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
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