From 0b52297f2288ca239e598afe6c92db83d8d2bfcd Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Tue, 23 Feb 2016 18:46:26 +0100 Subject: 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 Signed-off-by: Philipp Zabel --- drivers/reset/core.c | 59 ++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 48 insertions(+), 11 deletions(-) (limited to 'drivers/reset') diff --git a/drivers/reset/core.c b/drivers/reset/core.c index 957750600ff3..72b32bd15549 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 #include #include #include @@ -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; }; /** @@ -91,9 +96,14 @@ 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); @@ -104,26 +114,48 @@ 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); @@ -144,7 +176,7 @@ 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; @@ -152,6 +184,9 @@ 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; } @@ -167,6 +202,7 @@ 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; } @@ -185,7 +221,7 @@ 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; struct reset_controller_dev *r, *rcdev; @@ -235,7 +271,7 @@ 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); @@ -265,7 +301,7 @@ 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; @@ -274,7 +310,8 @@ 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); -- cgit v1.2.3-59-g8ed1b