[PATCH v4 3/3] reset: Add support for shared reset controls
Hans de Goede
hdegoede at redhat.com
Tue Feb 23 09:46:26 PST 2016
In some SoCs some hw-blocks share a reset control. Add support for this
setup by adding new:
reset_control_get_shared()
devm_reset_control_get_shared()
devm_reset_control_get_shared_by_index()
methods to get a reset_control. Note that this patch omits adding of_
variants, if these are needed later they can be easily added.
This patch also changes the behavior of the existing exclusive
reset_control_get() variants, if these are now called more then once
for the same reset_control they will return -EBUSY. To catch existing
drivers triggering this error (there should not be any) a WARN_ON(1)
is added in this path.
When a reset_control is shared, the behavior of reset_control_assert /
deassert is changed, for shared reset_controls these will work like the
clock-enable/disable and regulator-on/off functions. They will keep a
deassert_count, and only (re-)assert the reset after reset_control_assert
has been called as many times as reset_control_deassert was called.
Calling reset_control_assert without first calling reset_control_deassert
is not allowed on a shared reset control. Calling reset_control_reset is
also not allowed on a shared reset control.
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
drivers/reset/core.c | 59 +++++++++++++++++++++++++------
include/linux/reset.h | 96 +++++++++++++++++++++++++++++++++++++++++++--------
2 files changed, 129 insertions(+), 26 deletions(-)
diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index e439ae2..400e42f 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -8,6 +8,7 @@
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
+#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/export.h>
@@ -29,12 +30,16 @@ static LIST_HEAD(reset_controller_list);
* @id: ID of the reset controller in the reset
* controller device
* @refcnt: Number of gets of this reset_control
+ * @shared: Is this a shared (1), or an exclusive (0) reset_control?
+ * @deassert_cnt: Number of times this reset line has been deasserted
*/
struct reset_control {
struct reset_controller_dev *rcdev;
struct list_head list;
unsigned int id;
unsigned int refcnt;
+ int shared;
+ atomic_t deassert_count;
};
/**
@@ -94,9 +99,14 @@ EXPORT_SYMBOL_GPL(reset_controller_unregister);
/**
* reset_control_reset - reset the controlled device
* @rstc: reset controller
+ *
+ * Calling this on a shared reset controller is an error.
*/
int reset_control_reset(struct reset_control *rstc)
{
+ if (WARN_ON(rstc->shared))
+ return -EINVAL;
+
if (rstc->rcdev->ops->reset)
return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
@@ -107,26 +117,48 @@ EXPORT_SYMBOL_GPL(reset_control_reset);
/**
* reset_control_assert - asserts the reset line
* @rstc: reset controller
+ *
+ * Calling this on an exclusive reset controller guarantees that the reset
+ * will be asserted. When called on a shared reset controller the line may
+ * still be deasserted, as long as other users keep it so.
+ *
+ * For shared reset controls a driver cannot expect the hw's registers and
+ * internal state to be reset, but must be prepared for this to happen.
*/
int reset_control_assert(struct reset_control *rstc)
{
- if (rstc->rcdev->ops->assert)
- return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
+ if (!rstc->rcdev->ops->assert)
+ return -ENOTSUPP;
- return -ENOTSUPP;
+ if (rstc->shared) {
+ if (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
+ return -EINVAL;
+
+ if (atomic_dec_return(&rstc->deassert_count) != 0)
+ return 0;
+ }
+
+ return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
}
EXPORT_SYMBOL_GPL(reset_control_assert);
/**
* reset_control_deassert - deasserts the reset line
* @rstc: reset controller
+ *
+ * After calling this function, the reset is guaranteed to be deasserted.
*/
int reset_control_deassert(struct reset_control *rstc)
{
- if (rstc->rcdev->ops->deassert)
- return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
+ if (!rstc->rcdev->ops->deassert)
+ return -ENOTSUPP;
- return -ENOTSUPP;
+ if (rstc->shared) {
+ if (atomic_inc_return(&rstc->deassert_count) != 1)
+ return 0;
+ }
+
+ return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
}
EXPORT_SYMBOL_GPL(reset_control_deassert);
@@ -147,7 +179,7 @@ EXPORT_SYMBOL_GPL(reset_control_status);
static struct reset_control *__reset_control_get(
struct reset_controller_dev *rcdev,
- unsigned int index)
+ unsigned int index, int shared)
{
struct reset_control *rstc;
@@ -155,6 +187,9 @@ static struct reset_control *__reset_control_get(
list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
if (rstc->id == index) {
+ if (WARN_ON(!rstc->shared || !shared))
+ return ERR_PTR(-EBUSY);
+
rstc->refcnt++;
return rstc;
}
@@ -170,6 +205,7 @@ static struct reset_control *__reset_control_get(
list_add(&rstc->list, &rcdev->reset_control_head);
rstc->id = index;
rstc->refcnt = 1;
+ rstc->shared = shared;
return rstc;
}
@@ -188,7 +224,7 @@ static void __reset_control_put(struct reset_control *rstc)
}
struct reset_control *__of_reset_control_get(struct device_node *node,
- const char *id, int index)
+ const char *id, int index, int shared)
{
struct reset_control *rstc = ERR_PTR(-EPROBE_DEFER);
struct reset_controller_dev *r, *rcdev;
@@ -233,7 +269,7 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
}
/* reset_list_mutex also protects the rcdev's reset_control list */
- rstc = __reset_control_get(rcdev, rstc_id);
+ rstc = __reset_control_get(rcdev, rstc_id, shared);
mutex_unlock(&reset_list_mutex);
@@ -263,7 +299,7 @@ static void devm_reset_control_release(struct device *dev, void *res)
}
struct reset_control *__devm_reset_control_get(struct device *dev,
- const char *id, int index)
+ const char *id, int index, int shared)
{
struct reset_control **ptr, *rstc;
@@ -272,7 +308,8 @@ struct reset_control *__devm_reset_control_get(struct device *dev,
if (!ptr)
return ERR_PTR(-ENOMEM);
- rstc = __of_reset_control_get(dev ? dev->of_node : NULL, id, index);
+ rstc = __of_reset_control_get(dev ? dev->of_node : NULL,
+ id, index, shared);
if (!IS_ERR(rstc)) {
*ptr = rstc;
devres_add(dev, ptr);
diff --git a/include/linux/reset.h b/include/linux/reset.h
index 1bb69a2..a552134 100644
--- a/include/linux/reset.h
+++ b/include/linux/reset.h
@@ -13,10 +13,10 @@ int reset_control_deassert(struct reset_control *rstc);
int reset_control_status(struct reset_control *rstc);
struct reset_control *__of_reset_control_get(struct device_node *node,
- const char *id, int index);
+ const char *id, int index, int shared);
void reset_control_put(struct reset_control *rstc);
struct reset_control *__devm_reset_control_get(struct device *dev,
- const char *id, int index);
+ const char *id, int index, int shared);
int __must_check device_reset(struct device *dev);
@@ -63,14 +63,14 @@ static inline int device_reset_optional(struct device *dev)
static inline struct reset_control *__of_reset_control_get(
struct device_node *node,
- const char *id, int index)
+ const char *id, int index, int shared)
{
return ERR_PTR(-EINVAL);
}
static inline struct reset_control *__devm_reset_control_get(
struct device *dev,
- const char *id, int index)
+ const char *id, int index, int shared)
{
return ERR_PTR(-EINVAL);
}
@@ -78,11 +78,17 @@ static inline struct reset_control *__devm_reset_control_get(
#endif /* CONFIG_RESET_CONTROLLER */
/**
- * reset_control_get - Lookup and obtain a reference to a reset controller.
+ * reset_control_get - Lookup and obtain an exclusive reference to a
+ * reset controller.
* @dev: device to be reset by the controller
* @id: reset line name
*
* Returns a struct reset_control or IS_ERR() condition containing errno.
+ * If this function is called more then once for the same reset_control it will
+ * return -EBUSY.
+ *
+ * See reset_control_get_shared for details on shared references to
+ * reset-controls.
*
* Use of id names is optional.
*/
@@ -92,17 +98,46 @@ static inline struct reset_control *__must_check reset_control_get(
#ifndef CONFIG_RESET_CONTROLLER
WARN_ON(1);
#endif
- return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0);
+ return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, 0);
}
static inline struct reset_control *reset_control_get_optional(
struct device *dev, const char *id)
{
- return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0);
+ return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, 0);
}
/**
- * of_reset_control_get - Lookup and obtain a reference to a reset controller.
+ * reset_control_get_shared - Lookup and obtain a shared reference to a
+ * reset controller.
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Returns a struct reset_control or IS_ERR() condition containing errno.
+ * This function is intended for use with reset-controls which are shared
+ * between hardware-blocks.
+ *
+ * When a reset-control is shared, the behavior of reset_control_assert /
+ * deassert is changed, the reset-core will keep track of a deassert_count
+ * and only (re-)assert the reset after reset_control_assert has been called
+ * as many times as reset_control_deassert was called. Also see the remark
+ * about shared reset-controls in the reset_control_assert docs.
+ *
+ * Calling reset_control_assert without first calling reset_control_deassert
+ * is not allowed on a shared reset control. Calling reset_control_reset is
+ * also not allowed on a shared reset control.
+ *
+ * Use of id names is optional.
+ */
+static inline struct reset_control *reset_control_get_shared(
+ struct device *dev, const char *id)
+{
+ return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, 1);
+}
+
+/**
+ * of_reset_control_get - Lookup and obtain an exclusive reference to a
+ * reset controller.
* @node: device to be reset by the controller
* @id: reset line name
*
@@ -113,12 +148,12 @@ static inline struct reset_control *reset_control_get_optional(
static inline struct reset_control *of_reset_control_get(
struct device_node *node, const char *id)
{
- return __of_reset_control_get(node, id, 0);
+ return __of_reset_control_get(node, id, 0, 0);
}
/**
- * of_reset_control_get_by_index - Lookup and obtain a reference to a reset
- * controller by index.
+ * of_reset_control_get_by_index - Lookup and obtain an exclusive reference to
+ * a reset controller by index.
* @node: device to be reset by the controller
* @index: index of the reset controller
*
@@ -129,7 +164,7 @@ static inline struct reset_control *of_reset_control_get(
static inline struct reset_control *of_reset_control_get_by_index(
struct device_node *node, int index)
{
- return __of_reset_control_get(node, NULL, index);
+ return __of_reset_control_get(node, NULL, index, 0);
}
/**
@@ -147,13 +182,13 @@ static inline struct reset_control *__must_check devm_reset_control_get(
#ifndef CONFIG_RESET_CONTROLLER
WARN_ON(1);
#endif
- return __devm_reset_control_get(dev, id, 0);
+ return __devm_reset_control_get(dev, id, 0, 0);
}
static inline struct reset_control *devm_reset_control_get_optional(
struct device *dev, const char *id)
{
- return __devm_reset_control_get(dev, id, 0);
+ return __devm_reset_control_get(dev, id, 0, 0);
}
/**
@@ -168,7 +203,38 @@ static inline struct reset_control *devm_reset_control_get_optional(
static inline struct reset_control *devm_reset_control_get_by_index(
struct device *dev, int index)
{
- return __devm_reset_control_get(dev, NULL, index);
+ return __devm_reset_control_get(dev, NULL, index, 0);
+}
+
+/**
+ * devm_reset_control_get_shared - resource managed reset_control_get_shared()
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Managed reset_control_get_shared(). For reset controllers returned from
+ * this function, reset_control_put() is called automatically on driver detach.
+ * See reset_control_get_shared() for more information.
+ */
+static inline struct reset_control *devm_reset_control_get_shared(
+ struct device *dev, const char *id)
+{
+ return __devm_reset_control_get(dev, id, 0, 1);
+}
+
+/**
+ * devm_reset_control_get_shared_by_index - resource managed
+ * reset_control_get_shared
+ * @dev: device to be reset by the controller
+ * @index: index of the reset controller
+ *
+ * Managed reset_control_get_shared(). For reset controllers returned from
+ * this function, reset_control_put() is called automatically on driver detach.
+ * See reset_control_get_shared() for more information.
+ */
+static inline struct reset_control *devm_reset_control_get_shared_by_index(
+ struct device *dev, int index)
+{
+ return __devm_reset_control_get(dev, NULL, index, 1);
}
#endif
--
2.7.1
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