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Message-ID: <4beea5f252b056ba21f5e447e78cca17fbbf0e88.camel@pengutronix.de>
Date: Tue, 02 Nov 2021 12:26:09 +0100
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Sean Anderson <sean.anderson@...o.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] reset: Add GPIO-based reset controller
Hi Sean,
On Mon, 2021-10-25 at 14:17 -0400, Sean Anderson wrote:
[...]
> ping?
>
> Philipp, should I be CCing anyone else? MAINTAINERS only lists you and vger...
That is still correct. Maybe it is time to request a dedicated reset
driver mailing list for better visibility.
I was on vacation for a bit, but thankfully Rob already pointed you in
the right direction. I would like this to live in the core and continue
to use the established reset-gpios bindings.
I'm not sure whether adding a full reset_controller_dev for GPIO resets
is necessary. Maybe there is a good reasond for it, but I found adding a
gpio_desc pointer to struct reset_control and implementing non-shared
GPIO resets in the core would be trivial - I prototyped this at some
point (untested, see below).
To support shared resets, the already requested gpio_desc would have to
be found and used to retrieve the corresponding requested reset_control
from a list. This could probably be achieved by exporting gpiod_find()
from gpiolib.
----------8<----------
diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 61e688882643..b82acb38deb5 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -7,6 +7,8 @@
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/kref.h>
@@ -26,6 +28,8 @@ static LIST_HEAD(reset_lookup_list);
* struct reset_control - a reset control
* @rcdev: a pointer to the reset controller device
* this reset control belongs to
+ * @gpio: a pointer to the gpio_desc controlling the
+ * reset line, alternative to rcdev and id.
* @list: list entry for the rcdev's reset controller list
* @id: ID of the reset controller in the reset
* controller device
@@ -41,6 +45,7 @@ static LIST_HEAD(reset_lookup_list);
struct reset_control {
struct reset_controller_dev *rcdev;
struct list_head list;
+ struct gpio_desc *gpio;
unsigned int id;
struct kref refcnt;
bool acquired;
@@ -330,7 +335,8 @@ int reset_control_reset(struct reset_control *rstc)
if (!rstc)
return 0;
- if (WARN_ON(IS_ERR(rstc)))
+ if (WARN_ON(IS_ERR(rstc)) ||
+ WARN_ON(rstc->gpio))
return -EINVAL;
if (reset_control_is_array(rstc))
@@ -458,7 +464,14 @@ int reset_control_assert(struct reset_control *rstc)
if (atomic_dec_return(&rstc->deassert_count) != 0)
return 0;
+ }
+
+ if (rstc->gpio) {
+ gpiod_set_value(rstc->gpio, 1);
+ return 0;
+ }
+ if (rstc->shared) {
/*
* Shared reset controls allow the reset line to be in any state
* after this call, so doing nothing is a valid option.
@@ -551,6 +564,11 @@ int reset_control_deassert(struct reset_control *rstc)
}
}
+ if (rstc->gpio) {
+ gpiod_set_value(rstc->gpio, 0);
+ return 0;
+ }
+
/*
* If the reset controller does not implement .deassert(), we assume
* that it handles self-deasserting reset lines via .reset(). In that
@@ -559,7 +577,7 @@ int reset_control_deassert(struct reset_control *rstc)
* return -ENOTSUPP.
*/
if (!rstc->rcdev->ops->deassert)
- return 0;
+ return -ENOTSUPP;
return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
}
@@ -609,8 +627,10 @@ int reset_control_status(struct reset_control *rstc)
if (WARN_ON(IS_ERR(rstc)) || reset_control_is_array(rstc))
return -EINVAL;
- if (rstc->rcdev->ops->status)
+ if (rstc->rcdev && rstc->rcdev->ops->status)
return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
+ if (rstc->gpio)
+ return gpiod_get_value(rstc->gpio);
return -ENOTSUPP;
}
@@ -796,9 +816,11 @@ static void __reset_control_release(struct kref *kref)
lockdep_assert_held(&reset_list_mutex);
- module_put(rstc->rcdev->owner);
+ if (rstc->rcdev) {
+ module_put(rstc->rcdev->owner);
- list_del(&rstc->list);
+ list_del(&rstc->list);
+ }
kfree(rstc);
}
@@ -935,19 +957,66 @@ __reset_control_get_from_lookup(struct device *dev, const char *con_id,
return rstc;
}
+static struct reset_control *__reset_control_get_gpio(struct device *dev,
+ const char *id,
+ bool optional,
+ bool acquired)
+{
+ struct reset_control *rstc;
+ struct gpio_desc *gpio;
+ char prop[32];
+
+ if (id)
+ snprintf(prop, sizeof(prop), "%s-reset", id);
+ gpio = gpiod_get_optional(dev, id ? prop : "reset", GPIOD_ASIS);
+ if (IS_ERR(gpio))
+ return ERR_CAST(gpio);
+ if (!gpio)
+ return optional ? NULL : ERR_PTR(-ENOENT);
+
+ rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
+ if (!rstc) {
+ gpiod_put(gpio);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ /*
+ * Set the reset GPIO to output, deasserted, unless the GPIO is already
+ * set to output, asserted.
+ */
+ if (!(gpiod_get_direction(gpio) == GPIOF_DIR_OUT &&
+ gpiod_get_value(gpio) == 1))
+ gpiod_direction_output(gpio, 0);
+
+ rstc->gpio = gpio;
+ rstc->refcnt = 1;
+ rstc->acquired = acquired;
+ rstc->shared = false;
+
+ return rstc;
+}
+
struct reset_control *__reset_control_get(struct device *dev, const char *id,
int index, bool shared, bool optional,
bool acquired)
{
+ struct reset_control *rstc = ERR_PTR(-ENOENT);
+
if (WARN_ON(shared && acquired))
return ERR_PTR(-EINVAL);
if (dev->of_node)
- return __of_reset_control_get(dev->of_node, id, index, shared,
+ rstc = __of_reset_control_get(dev->of_node, id, index, shared,
optional, acquired);
+ if ((rstc == NULL || PTR_ERR(rstc) == -ENOENT) && index == 0 &&
+ shared == 0)
+ rstc = __reset_control_get_gpio(dev, id, optional, acquired);
+
+ if (rstc == NULL || PTR_ERR(rstc) == -ENOENT)
+ rstc = __reset_control_get_from_lookup(dev, id, shared,
+ optional, acquired);
- return __reset_control_get_from_lookup(dev, id, shared, optional,
- acquired);
+ return rstc;
}
EXPORT_SYMBOL_GPL(__reset_control_get);
---------->8----------
regards
Philipp
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