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reset: allow using reset_control_reset with shared reset

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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>
This commit is contained in:
Martin Blumenstingl 2016-11-12 14:13:03 +01:00 committed by Philipp Zabel
parent cdd24f76fe
commit 7da33a37b4
1 changed files with 37 additions and 6 deletions
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43
drivers/reset/core.c
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@ -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;
}