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Commit 7da33a37 authored by Martin Blumenstingl's avatar Martin Blumenstingl Committed by Philipp Zabel
Browse files

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: default avatarMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: default avatarPhilipp Zabel <p.zabel@pengutronix.de>
parent cdd24f76

drivers/reset/core.c

+37 −6
Original line number Diff line number Diff line
@@ -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))

		return -EINVAL;

	int ret;



	if (rstc->rcdev->ops->reset)

		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);

	if (WARN_ON(IS_ERR_OR_NULL(rstc)))

		return -EINVAL;



	if (!rstc->rcdev->ops->reset)

		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;

	}