diff mbox series

[v4,3/8] mfd: syscon: Add reference counting and device managed support

Message ID 20240805101725.93947-4-herve.codina@bootlin.com (mailing list archive)
State Superseded
Headers show
Series Add support for the LAN966x PCI device using a DT overlay | expand

Commit Message

Herve Codina Aug. 5, 2024, 10:17 a.m. UTC 
From: Clément Léger <clement.leger@bootlin.com>

Syscon releasing is not supported.
Without release function, unbinding a driver that uses syscon whether
explicitly or due to a module removal left the used syscon in a in-use
state.

For instance a syscon_node_to_regmap() call from a consumer retrieve a
syscon regmap instance. Internally, syscon_node_to_regmap() can create
syscon instance and add it to the existing syscon list. No API is
available to release this syscon instance, remove it from the list and
free it when it is not used anymore.

Introduce reference counting in syscon in order to keep track of syscon
usage using syscon_{get,put}() and add a device managed version of
syscon_regmap_lookup_by_phandle(), to automatically release the syscon
instance on the consumer removal.

Signed-off-by: Clément Léger <clement.leger@bootlin.com>
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/mfd/syscon.c       | 145 ++++++++++++++++++++++++++++++++++---
 include/linux/mfd/syscon.h |  16 ++++
 2 files changed, 152 insertions(+), 9 deletions(-)

Comments

Andy Shevchenko Aug. 5, 2024, 8:20 p.m. UTC | #1 
On Mon, Aug 5, 2024 at 12:19 PM Herve Codina <herve.codina@bootlin.com> wrote:
>
> From: Clément Léger <clement.leger@bootlin.com>
>
> Syscon releasing is not supported.
> Without release function, unbinding a driver that uses syscon whether
> explicitly or due to a module removal left the used syscon in a in-use
> state.
>
> For instance a syscon_node_to_regmap() call from a consumer retrieve a

retrieves?

> syscon regmap instance. Internally, syscon_node_to_regmap() can create
> syscon instance and add it to the existing syscon list. No API is
> available to release this syscon instance, remove it from the list and
> free it when it is not used anymore.
>
> Introduce reference counting in syscon in order to keep track of syscon
> usage using syscon_{get,put}() and add a device managed version of
> syscon_regmap_lookup_by_phandle(), to automatically release the syscon
> instance on the consumer removal.

...

> -       if (!syscon)
> +       if (!syscon) {
>                 syscon = of_syscon_register(np, check_res);
> +               if (IS_ERR(syscon))
> +                       return ERR_CAST(syscon);
> +       } else {
> +               syscon_get(syscon);
> +       }

  if (syscon)
    return syscon_get();

?

> +       return syscon;

...

> +static struct regmap *__devm_syscon_get(struct device *dev,
> +                                       struct syscon *syscon)
> +{
> +       struct syscon **ptr;
> +
> +       if (IS_ERR(syscon))
> +               return ERR_CAST(syscon);
> +
> +       ptr = devres_alloc(devm_syscon_release, sizeof(struct syscon *), GFP_KERNEL);
> +       if (!ptr) {
> +               syscon_put(syscon);
> +               return ERR_PTR(-ENOMEM);
> +       }
> +
> +       *ptr = syscon;
> +       devres_add(dev, ptr);
> +
> +       return syscon->regmap;

Can't the devm_add_action_or_reset() be used in this case? If so,
perhaps a comment to explain why?

> +}
Herve Codina Aug. 7, 2024, 1:29 p.m. UTC | #2 
Hi Andy,

On Mon, 5 Aug 2024 22:20:56 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Mon, Aug 5, 2024 at 12:19 PM Herve Codina <herve.codina@bootlin.com> wrote:
> >
> > From: Clément Léger <clement.leger@bootlin.com>
> >
> > Syscon releasing is not supported.
> > Without release function, unbinding a driver that uses syscon whether
> > explicitly or due to a module removal left the used syscon in a in-use
> > state.
> >
> > For instance a syscon_node_to_regmap() call from a consumer retrieve a  
> 
> retrieves?

Indeed, will be fixed.

> 
> > syscon regmap instance. Internally, syscon_node_to_regmap() can create
> > syscon instance and add it to the existing syscon list. No API is
> > available to release this syscon instance, remove it from the list and
> > free it when it is not used anymore.
> >
> > Introduce reference counting in syscon in order to keep track of syscon
> > usage using syscon_{get,put}() and add a device managed version of
> > syscon_regmap_lookup_by_phandle(), to automatically release the syscon
> > instance on the consumer removal.  
> 
> ...
> 
> > -       if (!syscon)
> > +       if (!syscon) {
> >                 syscon = of_syscon_register(np, check_res);
> > +               if (IS_ERR(syscon))
> > +                       return ERR_CAST(syscon);
> > +       } else {
> > +               syscon_get(syscon);
> > +       }  
> 
>   if (syscon)
>     return syscon_get();
> 
> ?
> 
> > +       return syscon;  

Yes and further more, I will remove also the unneeded IS_ERR() and ERR_CAST().
This will lead to just:

	if (syscon)
		return syscon_get(syscon);

	return of_syscon_register(np, check_res);

> 
> ...
> 
> > +static struct regmap *__devm_syscon_get(struct device *dev,
> > +                                       struct syscon *syscon)
> > +{
> > +       struct syscon **ptr;
> > +
> > +       if (IS_ERR(syscon))
> > +               return ERR_CAST(syscon);
> > +
> > +       ptr = devres_alloc(devm_syscon_release, sizeof(struct syscon *), GFP_KERNEL);
> > +       if (!ptr) {
> > +               syscon_put(syscon);
> > +               return ERR_PTR(-ENOMEM);
> > +       }
> > +
> > +       *ptr = syscon;
> > +       devres_add(dev, ptr);
> > +
> > +       return syscon->regmap;  
> 
> Can't the devm_add_action_or_reset() be used in this case? If so,
> perhaps a comment to explain why?

There is no reason to avoid the use of devm_add_action_or_reset() here.
So, I will use it in the next iteration.

Thanks for your review.

Best regards,
Hervé
diff mbox series

Patch

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 33f1e07ab24d..b602fa7c5c63 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -34,6 +34,7 @@  struct syscon {
 	struct regmap *regmap;
 	struct reset_control *reset;
 	struct list_head list;
+	struct kref refcount;
 };
 
 static const struct regmap_config syscon_regmap_config = {
@@ -147,6 +148,8 @@  static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 
 	syscon->regmap = regmap;
 	syscon->np = np;
+	of_node_get(syscon->np);
+	kref_init(&syscon->refcount);
 
 	spin_lock(&syscon_list_slock);
 	list_add_tail(&syscon->list, &syscon_list);
@@ -168,7 +171,30 @@  static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 	return ERR_PTR(ret);
 }
 
-static struct regmap *device_node_get_regmap(struct device_node *np,
+static void syscon_free(struct kref *kref)
+{
+	struct syscon *syscon = container_of(kref, struct syscon, refcount);
+
+	spin_lock(&syscon_list_slock);
+	list_del(&syscon->list);
+	spin_unlock(&syscon_list_slock);
+
+	regmap_exit(syscon->regmap);
+	of_node_put(syscon->np);
+	kfree(syscon);
+}
+
+static void syscon_get(struct syscon *syscon)
+{
+	kref_get(&syscon->refcount);
+}
+
+static void syscon_put(struct syscon *syscon)
+{
+	kref_put(&syscon->refcount, syscon_free);
+}
+
+static struct syscon *device_node_get_syscon(struct device_node *np,
 					     bool check_res)
 {
 	struct syscon *entry, *syscon = NULL;
@@ -183,9 +209,23 @@  static struct regmap *device_node_get_regmap(struct device_node *np,
 
 	spin_unlock(&syscon_list_slock);
 
-	if (!syscon)
+	if (!syscon) {
 		syscon = of_syscon_register(np, check_res);
+		if (IS_ERR(syscon))
+			return ERR_CAST(syscon);
+	} else {
+		syscon_get(syscon);
+	}
+
+	return syscon;
+}
 
+static struct regmap *device_node_get_regmap(struct device_node *np,
+					     bool check_res)
+{
+	struct syscon *syscon;
+
+	syscon = device_node_get_syscon(np, check_res);
 	if (IS_ERR(syscon))
 		return ERR_CAST(syscon);
 
@@ -246,12 +286,23 @@  struct regmap *device_node_to_regmap(struct device_node *np)
 }
 EXPORT_SYMBOL_GPL(device_node_to_regmap);
 
-struct regmap *syscon_node_to_regmap(struct device_node *np)
+static struct syscon *syscon_node_to_syscon(struct device_node *np)
 {
 	if (!of_device_is_compatible(np, "syscon"))
 		return ERR_PTR(-EINVAL);
 
-	return device_node_get_regmap(np, true);
+	return device_node_get_syscon(np, true);
+}
+
+struct regmap *syscon_node_to_regmap(struct device_node *np)
+{
+	struct syscon *syscon;
+
+	syscon = syscon_node_to_syscon(np);
+	if (IS_ERR(syscon))
+		return ERR_CAST(syscon);
+
+	return syscon->regmap;
 }
 EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
 
@@ -271,11 +322,11 @@  struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
 }
 EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
 
-struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
-					const char *property)
+static struct syscon *syscon_lookup_by_phandle(struct device_node *np,
+					       const char *property)
 {
 	struct device_node *syscon_np;
-	struct regmap *regmap;
+	struct syscon *syscon;
 
 	if (property)
 		syscon_np = of_parse_phandle(np, property, 0);
@@ -285,12 +336,24 @@  struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
 	if (!syscon_np)
 		return ERR_PTR(-ENODEV);
 
-	regmap = syscon_node_to_regmap(syscon_np);
+	syscon = syscon_node_to_syscon(syscon_np);
 
 	if (property)
 		of_node_put(syscon_np);
 
-	return regmap;
+	return syscon;
+}
+
+struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
+					       const char *property)
+{
+	struct syscon *syscon;
+
+	syscon = syscon_lookup_by_phandle(np, property);
+	if (IS_ERR(syscon))
+		return ERR_CAST(syscon);
+
+	return syscon->regmap;
 }
 EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);
 
@@ -341,6 +404,70 @@  struct regmap *syscon_regmap_lookup_by_phandle_optional(struct device_node *np,
 }
 EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle_optional);
 
+static struct syscon *syscon_from_regmap(struct regmap *regmap)
+{
+	struct syscon *entry, *syscon = NULL;
+
+	spin_lock(&syscon_list_slock);
+
+	list_for_each_entry(entry, &syscon_list, list)
+		if (entry->regmap == regmap) {
+			syscon = entry;
+			break;
+		}
+
+	spin_unlock(&syscon_list_slock);
+
+	return syscon;
+}
+
+void syscon_put_regmap(struct regmap *regmap)
+{
+	struct syscon *syscon;
+
+	syscon = syscon_from_regmap(regmap);
+	if (!syscon)
+		return;
+
+	syscon_put(syscon);
+}
+EXPORT_SYMBOL_GPL(syscon_put_regmap);
+
+static void devm_syscon_release(struct device *dev, void *res)
+{
+	syscon_put(*(struct syscon **)res);
+}
+
+static struct regmap *__devm_syscon_get(struct device *dev,
+					struct syscon *syscon)
+{
+	struct syscon **ptr;
+
+	if (IS_ERR(syscon))
+		return ERR_CAST(syscon);
+
+	ptr = devres_alloc(devm_syscon_release, sizeof(struct syscon *), GFP_KERNEL);
+	if (!ptr) {
+		syscon_put(syscon);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	*ptr = syscon;
+	devres_add(dev, ptr);
+
+	return syscon->regmap;
+}
+
+struct regmap *devm_syscon_regmap_lookup_by_phandle(struct device *dev,
+						    struct device_node *np,
+						    const char *property)
+{
+	struct syscon *syscon = syscon_lookup_by_phandle(np, property);
+
+	return __devm_syscon_get(dev, syscon);
+}
+EXPORT_SYMBOL_GPL(devm_syscon_regmap_lookup_by_phandle);
+
 static int syscon_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
index aad9c6b50463..a3025b4efb4a 100644
--- a/include/linux/mfd/syscon.h
+++ b/include/linux/mfd/syscon.h
@@ -15,6 +15,7 @@ 
 #include <linux/errno.h>
 
 struct device_node;
+struct device;
 
 #ifdef CONFIG_MFD_SYSCON
 struct regmap *device_node_to_regmap(struct device_node *np);
@@ -30,6 +31,10 @@  struct regmap *syscon_regmap_lookup_by_phandle_optional(struct device_node *np,
 							const char *property);
 int of_syscon_register_regmap(struct device_node *np,
 			      struct regmap *regmap);
+void syscon_put_regmap(struct regmap *regmap);
+struct regmap *devm_syscon_regmap_lookup_by_phandle(struct device *dev,
+						    struct device_node *np,
+						    const char *property);
 #else
 static inline struct regmap *device_node_to_regmap(struct device_node *np)
 {
@@ -73,6 +78,17 @@  static inline int of_syscon_register_regmap(struct device_node *np,
 					struct regmap *regmap)
 {
 	return -EOPNOTSUPP;
+
+static inline void syscon_put_regmap(struct regmap *regmap)
+{
+}
+
+static inline
+struct regmap *devm_syscon_regmap_lookup_by_phandle(struct device *dev,
+						    struct device_node *np,
+						    const char *property)
+{
+	return NULL;
 }
 
 #endif