diff mbox series

[v3,1/7] mfd: syscon: Add reference counting and device managed support

Message ID 20240627091137.370572-2-herve.codina@bootlin.com (mailing list archive)
State Superseded
Delegated to: Bjorn Helgaas
Headers show
Series Add support for the LAN966x PCI device using a DT overlay | expand

Commit Message

Herve Codina June 27, 2024, 9:11 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 |  18 +++++
 2 files changed, 154 insertions(+), 9 deletions(-)

Comments

Markus Elfring July 11, 2024, 4:09 p.m. UTC | #1 
…
> +++ b/drivers/mfd/syscon.c
…
> +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)
…
> +	spin_unlock(&syscon_list_slock);
> +
> +	return syscon;
> +}
…

Under which circumstances would you become interested to apply a statement
like “guard(spinlock)(&syscon_list_slock);”?
https://elixir.bootlin.com/linux/v6.10-rc7/source/include/linux/spinlock.h#L561

Regards,
Markus
Herve Codina July 11, 2024, 4:25 p.m. UTC | #2 
Hi Markus,

On Thu, 11 Jul 2024 18:09:26 +0200
Markus Elfring <Markus.Elfring@web.de> wrote:

> …
> > +++ b/drivers/mfd/syscon.c  
> …
> > +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)  
> …
> > +	spin_unlock(&syscon_list_slock);
> > +
> > +	return syscon;
> > +}  
> …
> 
> Under which circumstances would you become interested to apply a statement
> like “guard(spinlock)(&syscon_list_slock);”?
> https://elixir.bootlin.com/linux/v6.10-rc7/source/include/linux/spinlock.h#L561
> 

I used the spin_{lock,unlock}() pattern call already present in syscon.c.
Of course, I can add a new patch in this series converting syscon.c to
the guard() family and use guard() in my introduced lock/unlock.

Lee, any opinion ?

Best regards,
Hervé
Lee Jones July 11, 2024, 5:09 p.m. UTC | #3 
On Thu, 11 Jul 2024, Herve Codina wrote:

> Hi Markus,
> 
> On Thu, 11 Jul 2024 18:09:26 +0200
> Markus Elfring <Markus.Elfring@web.de> wrote:
> 
> > …
> > > +++ b/drivers/mfd/syscon.c  
> > …
> > > +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)  
> > …
> > > +	spin_unlock(&syscon_list_slock);
> > > +
> > > +	return syscon;
> > > +}  
> > …
> > 
> > Under which circumstances would you become interested to apply a statement
> > like “guard(spinlock)(&syscon_list_slock);”?
> > https://elixir.bootlin.com/linux/v6.10-rc7/source/include/linux/spinlock.h#L561
> > 
> 
> I used the spin_{lock,unlock}() pattern call already present in syscon.c.
> Of course, I can add a new patch in this series converting syscon.c to
> the guard() family and use guard() in my introduced lock/unlock.
> 
> Lee, any opinion ?

I'm intentionally leaving this one for Arnd.
diff mbox series

Patch

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 7d0e91164cba..86898831b842 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);
 
@@ -198,12 +238,23 @@  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);
 
@@ -223,11 +274,11 @@  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);
@@ -237,12 +288,24 @@  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);
 
@@ -293,6 +356,70 @@  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 c315903f6dab..f742d865a37a 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);
@@ -28,6 +29,11 @@  struct regmap *syscon_regmap_lookup_by_phandle_args(struct device_node *np,
 						    unsigned int *out_args);
 struct regmap *syscon_regmap_lookup_by_phandle_optional(struct device_node *np,
 							const char *property);
+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)
 {
@@ -67,6 +73,18 @@  static inline struct regmap *syscon_regmap_lookup_by_phandle_optional(
 	return NULL;
 }
 
+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
 
 #endif /* __LINUX_MFD_SYSCON_H__ */