reset: Add support for shared reset controls
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@redhat.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 9577506..72b32bd 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 @@
* @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;
};
/**
@@ -91,9 +96,14 @@
/**
* 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);
@@ -104,26 +114,48 @@
/**
* 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);
@@ -144,7 +176,7 @@
static struct reset_control *__reset_control_get(
struct reset_controller_dev *rcdev,
- unsigned int index)
+ unsigned int index, int shared)
{
struct reset_control *rstc;
@@ -152,6 +184,9 @@
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;
}
@@ -167,6 +202,7 @@
list_add(&rstc->list, &rcdev->reset_control_head);
rstc->id = index;
rstc->refcnt = 1;
+ rstc->shared = shared;
return rstc;
}
@@ -185,7 +221,7 @@
}
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;
struct reset_controller_dev *r, *rcdev;
@@ -235,7 +271,7 @@
}
/* 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);
@@ -265,7 +301,7 @@
}
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;
@@ -274,7 +310,8 @@
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);