On Thu, Feb 21, 2019 at 04:25:53PM +0100, Thierry Reding wrote: > From: Philipp Zabel <[email protected]> > > There are cases where a driver needs explicit control over a reset line > that is exclusively conneted to its device, but this control has to be > temporarily handed over to the power domain controller to handle reset > requirements during power transitions. > Allow multiple exclusive reset controls to be requested in 'released' > state for the same physical reset line, only one of which can be > acquired at the same time. > > Signed-off-by: Philipp Zabel <[email protected]> > Signed-off-by: Thierry Reding <[email protected]> > --- > drivers/reset/core.c | 139 ++++++++++++++++++++++++++++++++++++++---- > include/linux/reset.h | 93 ++++++++++++++++++++++------ > 2 files changed, 200 insertions(+), 32 deletions(-)
Hi Philipp, the bulk of this is unchanged relative to what you had posted originally. I squashed in the few things that we had already discussed earlier (EINVAL -> EPERM) and a couple of minor fixes for issues that I found while working with this. Attached is my fixup patch which contains all the changes I made on top of your version and that I squashed into this. Thierry --- >8 --- commit aa618d0b63eec676d9ea8db91a4c5fdc9330fc6b Author: Thierry Reding <[email protected]> Date: Mon Feb 18 11:32:46 2019 +0100 fixup! reset: add acquired/released state for exclusive reset controls diff --git a/drivers/reset/core.c b/drivers/reset/core.c index c6a7a4474142..1e8a42b16f23 100644 --- a/drivers/reset/core.c +++ b/drivers/reset/core.c @@ -65,6 +65,17 @@ struct reset_control_array { struct reset_control *rstc[]; }; +static const char *rcdev_name(struct reset_controller_dev *rcdev) +{ + if (rcdev->dev) + return dev_name(rcdev->dev); + + if (rcdev->of_node) + return rcdev->of_node->full_name; + + return NULL; +} + /** * of_reset_simple_xlate - translate reset_spec to the reset line number * @rcdev: a pointer to the reset controller device @@ -276,7 +287,7 @@ int reset_control_reset(struct reset_control *rstc) return 0; } else { if (!rstc->acquired) - return -EINVAL; + return -EPERM; } ret = rstc->rcdev->ops->reset(rstc->rcdev, rstc->id); @@ -340,8 +351,11 @@ int reset_control_assert(struct reset_control *rstc) if (!rstc->rcdev->ops->assert) return -ENOTSUPP; - if (!rstc->acquired) - return -EINVAL; + if (!rstc->acquired) { + WARN(1, "reset %s (ID: %u) is not acquired\n", + rcdev_name(rstc->rcdev), rstc->id); + return -EPERM; + } } return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id); @@ -378,8 +392,11 @@ int reset_control_deassert(struct reset_control *rstc) if (atomic_inc_return(&rstc->deassert_count) != 1) return 0; } else { - if (!rstc->acquired) - return -EINVAL; + if (!rstc->acquired) { + WARN(1, "reset %s (ID: %u) is not acquired\n", + rcdev_name(rstc->rcdev), rstc->id); + return -EPERM; + } } /* @@ -417,15 +434,43 @@ int reset_control_status(struct reset_control *rstc) } EXPORT_SYMBOL_GPL(reset_control_status); +/** + * reset_control_acquire() - acquires a reset control for exclusive use + * @rstc: reset control + * + * This is used to explicitly acquire a reset control for exclusive use. Note + * that exclusive resets are requested as acquired by default. In order for a + * second consumer to be able to control the reset, the first consumer has to + * release it first. Typically the easiest way to achieve this is to call the + * reset_control_get_exclusive_released() to obtain an instance of the reset + * control. Such reset controls are not acquired by default. + * + * Consumers implementing shared access to an exclusive reset need to follow + * a specific protocol in order to work together. Before consumers can change + * a reset they must acquire exclusive access using reset_control_acquire(). + * After they are done operating the reset, they must release exclusive access + * with a call to reset_control_release(). Consumers are not granted exclusive + * access to the reset as long as another consumer hasn't released a reset. + * + * See also: reset_control_release() + */ int reset_control_acquire(struct reset_control *rstc) { struct reset_control *rc; - if (!rstc || rstc->acquired) + if (!rstc) return 0; + if (WARN_ON(IS_ERR(rstc))) + return -EINVAL; + mutex_lock(&reset_list_mutex); + if (rstc->acquired) { + mutex_unlock(&reset_list_mutex); + return 0; + } + list_for_each_entry(rc, &rstc->rcdev->reset_control_head, list) { if (rstc != rc && rstc->id == rc->id) { if (rc->acquired) { @@ -435,13 +480,28 @@ int reset_control_acquire(struct reset_control *rstc) } } + rstc->acquired = true; + mutex_unlock(&reset_list_mutex); return 0; } EXPORT_SYMBOL_GPL(reset_control_acquire); +/** + * reset_control_release() - releases exclusive access to a reset control + * @rstc: reset control + * + * Releases exclusive access right to a reset control previously obtained by a + * call to reset_control_acquire(). Until a consumer calls this function, no + * other consumers will be granted exclusive access. + * + * See also: reset_control_acquire() + */ void reset_control_release(struct reset_control *rstc) { + if (!rstc || WARN_ON(IS_ERR(rstc))) + return; + rstc->acquired = false; } EXPORT_SYMBOL_GPL(reset_control_release);
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