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Subject[PATCH v2 2/6] hwspinlock: allow sharing of hwspinlocks
Date
The current implementation does not allow different devices to use a
common hwspinlock. Offer the possibility to use the same hwspinlock by
several users.
If a device registers to the framework with #hwlock-cells = 2, then
the second parameter of the 'hwlocks' DeviceTree property defines
whether an hwlock is requested for an exclusive or a shared usage.
If a device registers with #hwlock-cells = 1, then all the hwlocks are
for an exclusive usage.

Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
---
Documentation/hwspinlock.txt | 10 ++--
drivers/hwspinlock/hwspinlock_core.c | 82 +++++++++++++++++++++++++-------
drivers/hwspinlock/hwspinlock_internal.h | 2 +
3 files changed, 73 insertions(+), 21 deletions(-)

diff --git a/Documentation/hwspinlock.txt b/Documentation/hwspinlock.txt
index ed640a2..e6ce2dd 100644
--- a/Documentation/hwspinlock.txt
+++ b/Documentation/hwspinlock.txt
@@ -54,9 +54,11 @@ Should be called from a process context (might sleep).
struct hwspinlock *hwspin_lock_request_specific(unsigned int id);

Assign a specific hwspinlock id and return its address, or NULL
-if that hwspinlock is already in use. Usually board code will
-be calling this function in order to reserve specific hwspinlock
-ids for predefined purposes.
+if that hwspinlock is already in use and not shared. If that specific
+hwspinlock is declared as shared, it can be requested and used by
+several users.
+Usually board code will be calling this function in order to reserve
+specific hwspinlock ids for predefined purposes.

Should be called from a process context (might sleep).

@@ -368,11 +370,13 @@ of which represents a single hardware lock::
* struct hwspinlock - this struct represents a single hwspinlock instance
* @bank: the hwspinlock_device structure which owns this lock
* @lock: initialized and used by hwspinlock core
+ * @refcount: number of users (when shared)
* @priv: private data, owned by the underlying platform-specific hwspinlock drv
*/
struct hwspinlock {
struct hwspinlock_device *bank;
spinlock_t lock;
+ unsigned int refcount;
void *priv;
};

diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 2bad40d..53afdeb 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -25,6 +25,8 @@

/* radix tree tags */
#define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */
+#define HWSPINLOCK_EXCLUSIVE (1) /* tags an hwspinlock as exclusive */
+#define HWSPINLOCK_SHARED (2) /* tags an hwspinlock as shared */

/*
* A radix tree is used to maintain the available hwspinlock instances.
@@ -291,7 +293,7 @@ EXPORT_SYMBOL_GPL(__hwspin_unlock);
* @hwlock_spec: hwlock specifier as found in the device tree
*
* This is a simple translation function, suitable for hwspinlock platform
- * drivers that only has a lock specifier length of 1.
+ * drivers that only has a lock specifier length of 1 or 2.
*
* Returns a relative index of the lock within a specified bank on success,
* or -EINVAL on invalid specifier cell count.
@@ -299,7 +301,8 @@ EXPORT_SYMBOL_GPL(__hwspin_unlock);
static inline int
of_hwspin_lock_simple_xlate(const struct of_phandle_args *hwlock_spec)
{
- if (WARN_ON(hwlock_spec->args_count != 1))
+ if (WARN_ON(hwlock_spec->args_count != 1 &&
+ hwlock_spec->args_count != 2))
return -EINVAL;

return hwlock_spec->args[0];
@@ -322,11 +325,12 @@ of_hwspin_lock_simple_xlate(const struct of_phandle_args *hwlock_spec)
int of_hwspin_lock_get_id(struct device_node *np, int index)
{
struct of_phandle_args args;
- struct hwspinlock *hwlock;
+ struct hwspinlock *hwlock, *tmp;
struct radix_tree_iter iter;
void **slot;
int id;
int ret;
+ unsigned int tag;

ret = of_parse_phandle_with_args(np, "hwlocks", "#hwlock-cells", index,
&args);
@@ -361,6 +365,37 @@ int of_hwspin_lock_get_id(struct device_node *np, int index)
}
id += hwlock->bank->base_id;

+ /* Set the EXCLUSIVE / SHARED tag */
+ if (args.args_count == 2 && args.args[1]) {
+ /* Tag SHARED unless already tagged EXCLUSIVE */
+ if (radix_tree_tag_get(&hwspinlock_tree, id,
+ HWSPINLOCK_EXCLUSIVE)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ tag = HWSPINLOCK_SHARED;
+ } else {
+ /* Tag EXCLUSIVE unless already tagged SHARED */
+ if (radix_tree_tag_get(&hwspinlock_tree, id,
+ HWSPINLOCK_SHARED)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ tag = HWSPINLOCK_EXCLUSIVE;
+ }
+
+ /* mark this hwspinlock */
+ hwlock = radix_tree_lookup(&hwspinlock_tree, id);
+ if (!hwlock) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ tmp = radix_tree_tag_set(&hwspinlock_tree, id, tag);
+
+ /* self-sanity check which should never fail */
+ WARN_ON(tmp != hwlock);
+
out:
of_node_put(args.np);
return ret ? ret : id;
@@ -483,6 +518,7 @@ int hwspin_lock_register(struct hwspinlock_device *bank, struct device *dev,

spin_lock_init(&hwlock->lock);
hwlock->bank = bank;
+ hwlock->refcount = 0;

ret = hwspin_lock_register_single(hwlock, base_id + i);
if (ret)
@@ -625,7 +661,7 @@ static int __hwspin_lock_request(struct hwspinlock *hwlock)
{
struct device *dev = hwlock->bank->dev;
struct hwspinlock *tmp;
- int ret;
+ int ret, id;

/* prevent underlying implementation from being removed */
if (!try_module_get(dev->driver->owner)) {
@@ -642,13 +678,18 @@ static int __hwspin_lock_request(struct hwspinlock *hwlock)
return ret;
}

+ /* update shareable refcount */
+ id = hwlock_to_id(hwlock);
+ if (radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_SHARED) &&
+ hwlock->refcount++)
+ goto out;
+
/* mark hwspinlock as used, should not fail */
- tmp = radix_tree_tag_clear(&hwspinlock_tree, hwlock_to_id(hwlock),
- HWSPINLOCK_UNUSED);
+ tmp = radix_tree_tag_clear(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);

/* self-sanity check that should never fail */
WARN_ON(tmp != hwlock);
-
+out:
return ret;
}

@@ -742,9 +783,9 @@ struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
/* sanity check (this shouldn't happen) */
WARN_ON(hwlock_to_id(hwlock) != id);

- /* make sure this hwspinlock is unused */
- ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
- if (ret == 0) {
+ /* make sure this hwspinlock is unused or shareable */
+ if (!radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_SHARED) &&
+ !radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED)) {
pr_warn("hwspinlock %u is already in use\n", id);
hwlock = NULL;
goto out;
@@ -777,7 +818,7 @@ int hwspin_lock_free(struct hwspinlock *hwlock)
{
struct device *dev;
struct hwspinlock *tmp;
- int ret;
+ int ret, id;

if (!hwlock) {
pr_err("invalid hwlock\n");
@@ -788,30 +829,35 @@ int hwspin_lock_free(struct hwspinlock *hwlock)
mutex_lock(&hwspinlock_tree_lock);

/* make sure the hwspinlock is used */
- ret = radix_tree_tag_get(&hwspinlock_tree, hwlock_to_id(hwlock),
- HWSPINLOCK_UNUSED);
+ id = hwlock_to_id(hwlock);
+ ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
if (ret == 1) {
dev_err(dev, "%s: hwlock is already free\n", __func__);
dump_stack();
ret = -EINVAL;
- goto out;
+ goto unlock;
}

/* notify the underlying device that power is not needed */
ret = pm_runtime_put(dev);
if (ret < 0)
- goto out;
+ goto unlock;
+
+ /* update shareable refcount */
+ if (radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_SHARED) &&
+ --hwlock->refcount)
+ goto put;

/* mark this hwspinlock as available */
- tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock),
- HWSPINLOCK_UNUSED);
+ tmp = radix_tree_tag_set(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);

/* sanity check (this shouldn't happen) */
WARN_ON(tmp != hwlock);

+put:
module_put(dev->driver->owner);

-out:
+unlock:
mutex_unlock(&hwspinlock_tree_lock);
return ret;
}
diff --git a/drivers/hwspinlock/hwspinlock_internal.h b/drivers/hwspinlock/hwspinlock_internal.h
index 9eb6bd0..c808e11 100644
--- a/drivers/hwspinlock/hwspinlock_internal.h
+++ b/drivers/hwspinlock/hwspinlock_internal.h
@@ -35,11 +35,13 @@ struct hwspinlock_ops {
* struct hwspinlock - this struct represents a single hwspinlock instance
* @bank: the hwspinlock_device structure which owns this lock
* @lock: initialized and used by hwspinlock core
+ * @refcount: number of users (when shared)
* @priv: private data, owned by the underlying platform-specific hwspinlock drv
*/
struct hwspinlock {
struct hwspinlock_device *bank;
spinlock_t lock;
+ unsigned int refcount;
void *priv;
};

--
2.7.4
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