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authorMartin Blumenstingl <martin.blumenstingl@googlemail.com>2016-11-12 14:13:03 +0100
committerPhilipp Zabel <p.zabel@pengutronix.de>2016-11-14 09:58:28 +0100
commit7da33a37b48f11ffcb4a718f29a3d4552423fea1 (patch)
tree12cd41d58ed7e3e48389b4cc2a11e8a8686cd36a /drivers/reset/core.c
parentcdd24f76fe84fd6ee3b46f54b2a475d04d79889d (diff)
downloadlinux-stericsson-7da33a37b48f11ffcb4a718f29a3d4552423fea1.tar.gz
reset: allow using reset_control_reset with shared reset
Some SoCs (for example Amlogic GXBB) implement a reset controller which only supports a reset pulse (triggered via reset_control_reset). At the same time multiple devices (in case of the Amlogic GXBB SoC both USB PHYs) are sharing the same reset line. This patch allows using reset_control_reset also for shared resets. There are limitations though: reset_control_reset can only be used if reset_control_assert was not used yet. reset_control_assert can only be used if reset_control_reset was not used yet. For shared resets the reset is only triggered once for the lifetime of the reset_control instance (the reset can be triggered again if all consumers of that specific reset_control are gone, as the reset framework will free the reset_control instance in that case). Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Diffstat (limited to 'drivers/reset/core.c')
-rw-r--r--drivers/reset/core.c43
1 files changed, 37 insertions, 6 deletions
diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index b8ae1dbd4c17..10368ed8fd13 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -32,6 +32,9 @@ static LIST_HEAD(reset_controller_list);
* @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
+ * @triggered_count: Number of times this reset line has been reset. Currently
+ * only used for shared resets, which means that the value
+ * will be either 0 or 1.
*/
struct reset_control {
struct reset_controller_dev *rcdev;
@@ -40,6 +43,7 @@ struct reset_control {
unsigned int refcnt;
int shared;
atomic_t deassert_count;
+ atomic_t triggered_count;
};
/**
@@ -134,18 +138,35 @@ EXPORT_SYMBOL_GPL(devm_reset_controller_register);
* reset_control_reset - reset the controlled device
* @rstc: reset controller
*
- * Calling this on a shared reset controller is an error.
+ * On a shared reset line the actual reset pulse is only triggered once for the
+ * lifetime of the reset_control instance: for all but the first caller this is
+ * a no-op.
+ * Consumers must not use reset_control_(de)assert on shared reset lines when
+ * reset_control_reset has been used.
*/
int reset_control_reset(struct reset_control *rstc)
{
- if (WARN_ON(IS_ERR_OR_NULL(rstc)) ||
- WARN_ON(rstc->shared))
+ int ret;
+
+ if (WARN_ON(IS_ERR_OR_NULL(rstc)))
return -EINVAL;
- if (rstc->rcdev->ops->reset)
- return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
+ if (!rstc->rcdev->ops->reset)
+ return -ENOTSUPP;
- return -ENOTSUPP;
+ if (rstc->shared) {
+ if (WARN_ON(atomic_read(&rstc->deassert_count) != 0))
+ return -EINVAL;
+
+ if (atomic_inc_return(&rstc->triggered_count) != 1)
+ return 0;
+ }
+
+ ret = rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
+ if (rstc->shared && !ret)
+ atomic_dec(&rstc->triggered_count);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(reset_control_reset);
@@ -159,6 +180,8 @@ EXPORT_SYMBOL_GPL(reset_control_reset);
*
* 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.
+ * Consumers must not use reset_control_reset on shared reset lines when
+ * reset_control_(de)assert has been used.
*/
int reset_control_assert(struct reset_control *rstc)
{
@@ -169,6 +192,9 @@ int reset_control_assert(struct reset_control *rstc)
return -ENOTSUPP;
if (rstc->shared) {
+ if (WARN_ON(atomic_read(&rstc->triggered_count) != 0))
+ return -EINVAL;
+
if (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
return -EINVAL;
@@ -185,6 +211,8 @@ EXPORT_SYMBOL_GPL(reset_control_assert);
* @rstc: reset controller
*
* After calling this function, the reset is guaranteed to be deasserted.
+ * Consumers must not use reset_control_reset on shared reset lines when
+ * reset_control_(de)assert has been used.
*/
int reset_control_deassert(struct reset_control *rstc)
{
@@ -195,6 +223,9 @@ int reset_control_deassert(struct reset_control *rstc)
return -ENOTSUPP;
if (rstc->shared) {
+ if (WARN_ON(atomic_read(&rstc->triggered_count) != 0))
+ return -EINVAL;
+
if (atomic_inc_return(&rstc->deassert_count) != 1)
return 0;
}