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SubjectRe: [PATCH] reset: Add reset controller API
An update on the patch title, since we don't add an API but extend it,
The title should rather be: Add a new call to the reset framework

Le jeu. 1 oct. 2020 à 15:28, Amjad Ouled-Ameur
<aouledameur@baylibre.com> a écrit :
>
> The current reset framework API does not allow to release what is done by
> reset_control_reset(), IOW decrement triggered_count. Add the new
> reset_control_resettable() call to do so.
>
> When reset_control_reset() has been called once, the counter
> triggered_count, in the reset framework, is incremented i.e the resource
> under the reset is in-use and the reset should not be done again.
> reset_control_resettable() would be the way to state that the resource is
> no longer used and, that from the caller's perspective, the reset can be
> fired again if necessary.
>
> This patch will fix a usb suspend warning seen on the libretech-cc
> related to the shared reset line. This warning was addressed by the
> previously reverted commit 7a410953d1fb ("usb: dwc3: meson-g12a: fix shared
> reset control use")
>
> Signed-off-by: Amjad Ouled-Ameur <aouledameur@baylibre.com>
> Reported-by: Jerome Brunet <jbrunet@baylibre.com>
> ---
> drivers/reset/core.c | 57 +++++++++++++++++++++++++++++++++++++++++++
> include/linux/reset.h | 1 +
> 2 files changed, 58 insertions(+)
>
> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
> index 01c0c7aa835c..53653d4b55c4 100644
> --- a/drivers/reset/core.c
> +++ b/drivers/reset/core.c
> @@ -207,6 +207,19 @@ static int reset_control_array_reset(struct reset_control_array *resets)
> return 0;
> }
>
> +static int reset_control_array_resettable(struct reset_control_array *resets)
> +{
> + int ret, i;
> +
> + for (i = 0; i < resets->num_rstcs; i++) {
> + ret = reset_control_resettable(resets->rstc[i]);
> + if (ret)
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> static int reset_control_array_assert(struct reset_control_array *resets)
> {
> int ret, i;
> @@ -324,6 +337,50 @@ int reset_control_reset(struct reset_control *rstc)
> }
> EXPORT_SYMBOL_GPL(reset_control_reset);
>
> +/**
> + * reset_control_resettable - decrements triggered_count of the controlled device
> + * @rstc: reset controller
> + *
> + * On a shared reset line the actual reset pulse is only triggered once for the
> + * lifetime of the reset_control instance, except if this function is used.
> + * In fact, It decrements triggered_count that makes sure of not allowing
> + * a reset if triggered_count is not null.
> + *
> + * This is a no-op in case triggered_count is already null i.e shared reset line
> + * is ready to be triggered.
> + *
> + * Consumers must not use reset_control_(de)assert on shared reset lines when
> + * reset_control_reset has been used.
> + *
> + * If rstc is NULL it is an optional clear and the function will just
> + * return 0.
> + */
> +int reset_control_resettable(struct reset_control *rstc)
> +{
> + if (!rstc)
> + return 0;
> +
> + if (WARN_ON(IS_ERR(rstc)))
> + return -EINVAL;
> +
> + if (reset_control_is_array(rstc))
> + return reset_control_array_resettable(rstc_to_array(rstc));
> +
> + if (rstc->shared) {
> + if (WARN_ON(atomic_read(&rstc->deassert_count) != 0))
> + return -EINVAL;
> +
> + if (atomic_read(&rstc->triggered_count) > 0)
> + atomic_dec(&rstc->triggered_count);
> + } else {
> + if (!rstc->acquired)
> + return -EPERM;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(reset_control_resettable);
> +
> /**
> * reset_control_assert - asserts the reset line
> * @rstc: reset controller
> diff --git a/include/linux/reset.h b/include/linux/reset.h
> index 05aa9f440f48..ffa447d0d1d6 100644
> --- a/include/linux/reset.h
> +++ b/include/linux/reset.h
> @@ -13,6 +13,7 @@ struct reset_control;
> #ifdef CONFIG_RESET_CONTROLLER
>
> int reset_control_reset(struct reset_control *rstc);
> +int reset_control_resettable(struct reset_control *rstc);
> int reset_control_assert(struct reset_control *rstc);
> int reset_control_deassert(struct reset_control *rstc);
> int reset_control_status(struct reset_control *rstc);
> --
> 2.17.1
>


--
Amjad Ouled-Ameur
Embedded Linux Engineer - Villeneuve Loubet, FR
Engit@BayLibre - At the Heart of Embedded Linux

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