[v5,01/11] firmware: raspberrypi: Keep count of all consumers
diff mbox series

Message ID 20201123183833.18750-2-nsaenzjulienne@suse.de
State New, archived
Headers show
Series
  • Raspberry Pi PoE HAT fan support
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Commit Message

Nicolas Saenz Julienne Nov. 23, 2020, 6:38 p.m. UTC
When unbinding the firmware device we need to make sure it has no
consumers left. Otherwise we'd leave them with a firmware handle
pointing at freed memory.

Keep a reference count of all consumers and introduce rpi_firmware_put()
which will permit automatically decrease the reference count upon
unbinding consumer drivers.

Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---

Changes since v3:
- Use kref instead of waiting on refcount

 drivers/firmware/raspberrypi.c             | 37 +++++++++++++++++++---
 include/soc/bcm2835/raspberrypi-firmware.h |  2 ++
 2 files changed, 35 insertions(+), 4 deletions(-)

Comments

Florian Fainelli Dec. 2, 2020, 5:26 p.m. UTC | #1
On 11/23/2020 10:38 AM, Nicolas Saenz Julienne wrote:
> When unbinding the firmware device we need to make sure it has no
> consumers left. Otherwise we'd leave them with a firmware handle
> pointing at freed memory.
> 
> Keep a reference count of all consumers and introduce rpi_firmware_put()
> which will permit automatically decrease the reference count upon
> unbinding consumer drivers.
> 
> Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

This looks fine to me, just one nit below:

[snip]

>  /**
> - * rpi_firmware_get - Get pointer to rpi_firmware structure.

Is not removing this line going to create a kernel doc warning?

With that fixed:

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Bartosz Golaszewski Dec. 3, 2020, 8:05 a.m. UTC | #2
On Mon, Nov 23, 2020 at 7:38 PM Nicolas Saenz Julienne
<nsaenzjulienne@suse.de> wrote:
>
> When unbinding the firmware device we need to make sure it has no
> consumers left. Otherwise we'd leave them with a firmware handle
> pointing at freed memory.
>
> Keep a reference count of all consumers and introduce rpi_firmware_put()
> which will permit automatically decrease the reference count upon
> unbinding consumer drivers.
>
> Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> ---
>
> Changes since v3:
> - Use kref instead of waiting on refcount
>
>  drivers/firmware/raspberrypi.c             | 37 +++++++++++++++++++---
>  include/soc/bcm2835/raspberrypi-firmware.h |  2 ++
>  2 files changed, 35 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
> index 30259dc9b805..ed793aef7851 100644
> --- a/drivers/firmware/raspberrypi.c
> +++ b/drivers/firmware/raspberrypi.c
> @@ -7,6 +7,7 @@
>   */
>
>  #include <linux/dma-mapping.h>
> +#include <linux/kref.h>
>  #include <linux/mailbox_client.h>
>  #include <linux/module.h>
>  #include <linux/of_platform.h>
> @@ -27,6 +28,8 @@ struct rpi_firmware {
>         struct mbox_chan *chan; /* The property channel. */
>         struct completion c;
>         u32 enabled;
> +
> +       struct kref consumers;
>  };
>
>  static DEFINE_MUTEX(transaction_lock);
> @@ -225,12 +228,27 @@ static void rpi_register_clk_driver(struct device *dev)
>                                                 -1, NULL, 0);
>  }
>
> +static void rpi_firmware_delete(struct kref *kref)
> +{
> +       struct rpi_firmware *fw = container_of(kref, struct rpi_firmware,
> +                                              consumers);
> +
> +       mbox_free_channel(fw->chan);
> +       kfree(fw);
> +}
> +
> +void rpi_firmware_put(struct rpi_firmware *fw)
> +{
> +       kref_put(&fw->consumers, rpi_firmware_delete);
> +}
> +EXPORT_SYMBOL_GPL(rpi_firmware_put);
> +
>  static int rpi_firmware_probe(struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
>         struct rpi_firmware *fw;
>
> -       fw = devm_kzalloc(dev, sizeof(*fw), GFP_KERNEL);

One nit from my side: maybe add a comment here saying that you really
want to use non-managed kzalloc() because you're going to get people
blindly converting it to devm_kzalloc() very soon.

Bartosz

> +       fw = kzalloc(sizeof(*fw), GFP_KERNEL);
>         if (!fw)
>                 return -ENOMEM;
>
> @@ -247,6 +265,7 @@ static int rpi_firmware_probe(struct platform_device *pdev)
>         }
>
>         init_completion(&fw->c);
> +       kref_init(&fw->consumers);
>
>         platform_set_drvdata(pdev, fw);
>
> @@ -275,25 +294,35 @@ static int rpi_firmware_remove(struct platform_device *pdev)
>         rpi_hwmon = NULL;
>         platform_device_unregister(rpi_clk);
>         rpi_clk = NULL;
> -       mbox_free_channel(fw->chan);
> +
> +       rpi_firmware_put(fw);
>
>         return 0;
>  }
>
>  /**
> - * rpi_firmware_get - Get pointer to rpi_firmware structure.
>   * @firmware_node:    Pointer to the firmware Device Tree node.
>   *
> + * The reference to rpi_firmware has to be released with rpi_firmware_put().
> + *
>   * Returns NULL is the firmware device is not ready.
>   */
>  struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
>  {
>         struct platform_device *pdev = of_find_device_by_node(firmware_node);
> +       struct rpi_firmware *fw;
>
>         if (!pdev)
>                 return NULL;
>
> -       return platform_get_drvdata(pdev);
> +       fw = platform_get_drvdata(pdev);
> +       if (!fw)
> +               return NULL;
> +
> +       if (!kref_get_unless_zero(&fw->consumers))
> +               return NULL;
> +
> +       return fw;
>  }
>  EXPORT_SYMBOL_GPL(rpi_firmware_get);
>
> diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
> index cc9cdbc66403..fdfef7fe40df 100644
> --- a/include/soc/bcm2835/raspberrypi-firmware.h
> +++ b/include/soc/bcm2835/raspberrypi-firmware.h
> @@ -140,6 +140,7 @@ int rpi_firmware_property(struct rpi_firmware *fw,
>                           u32 tag, void *data, size_t len);
>  int rpi_firmware_property_list(struct rpi_firmware *fw,
>                                void *data, size_t tag_size);
> +void rpi_firmware_put(struct rpi_firmware *fw);
>  struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node);
>  #else
>  static inline int rpi_firmware_property(struct rpi_firmware *fw, u32 tag,
> @@ -154,6 +155,7 @@ static inline int rpi_firmware_property_list(struct rpi_firmware *fw,
>         return -ENOSYS;
>  }
>
> +static inline void rpi_firmware_put(struct rpi_firmware *fw) { }
>  static inline struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
>  {
>         return NULL;
> --
> 2.29.2
>
Nicolas Saenz Julienne Dec. 3, 2020, 8:53 a.m. UTC | #3
On Thu, 2020-12-03 at 09:05 +0100, Bartosz Golaszewski wrote:
> On Mon, Nov 23, 2020 at 7:38 PM Nicolas Saenz Julienne
> <nsaenzjulienne@suse.de> wrote:
> > 
> > When unbinding the firmware device we need to make sure it has no
> > consumers left. Otherwise we'd leave them with a firmware handle
> > pointing at freed memory.
> > 
> > Keep a reference count of all consumers and introduce rpi_firmware_put()
> > which will permit automatically decrease the reference count upon
> > unbinding consumer drivers.
> > 
> > Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> > ---
> > 
> > Changes since v3:
> > - Use kref instead of waiting on refcount
> > 
> >  drivers/firmware/raspberrypi.c             | 37 +++++++++++++++++++---
> >  include/soc/bcm2835/raspberrypi-firmware.h |  2 ++
> >  2 files changed, 35 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
> > index 30259dc9b805..ed793aef7851 100644
> > --- a/drivers/firmware/raspberrypi.c
> > +++ b/drivers/firmware/raspberrypi.c
> > @@ -7,6 +7,7 @@
> >   */
> > 
> >  #include <linux/dma-mapping.h>
> > +#include <linux/kref.h>
> >  #include <linux/mailbox_client.h>
> >  #include <linux/module.h>
> >  #include <linux/of_platform.h>
> > @@ -27,6 +28,8 @@ struct rpi_firmware {
> >         struct mbox_chan *chan; /* The property channel. */
> >         struct completion c;
> >         u32 enabled;
> > +
> > +       struct kref consumers;
> >  };
> > 
> >  static DEFINE_MUTEX(transaction_lock);
> > @@ -225,12 +228,27 @@ static void rpi_register_clk_driver(struct device *dev)
> >                                                 -1, NULL, 0);
> >  }
> > 
> > +static void rpi_firmware_delete(struct kref *kref)
> > +{
> > +       struct rpi_firmware *fw = container_of(kref, struct rpi_firmware,
> > +                                              consumers);
> > +
> > +       mbox_free_channel(fw->chan);
> > +       kfree(fw);
> > +}
> > +
> > +void rpi_firmware_put(struct rpi_firmware *fw)
> > +{
> > +       kref_put(&fw->consumers, rpi_firmware_delete);
> > +}
> > +EXPORT_SYMBOL_GPL(rpi_firmware_put);
> > +
> >  static int rpi_firmware_probe(struct platform_device *pdev)
> >  {
> >         struct device *dev = &pdev->dev;
> >         struct rpi_firmware *fw;
> > 
> > -       fw = devm_kzalloc(dev, sizeof(*fw), GFP_KERNEL);
> 
> One nit from my side: maybe add a comment here saying that you really
> want to use non-managed kzalloc() because you're going to get people
> blindly converting it to devm_kzalloc() very soon.

Good point, I'll change it.

Regards,
Nicolas

Patch
diff mbox series

diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
index 30259dc9b805..ed793aef7851 100644
--- a/drivers/firmware/raspberrypi.c
+++ b/drivers/firmware/raspberrypi.c
@@ -7,6 +7,7 @@ 
  */
 
 #include <linux/dma-mapping.h>
+#include <linux/kref.h>
 #include <linux/mailbox_client.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
@@ -27,6 +28,8 @@  struct rpi_firmware {
 	struct mbox_chan *chan; /* The property channel. */
 	struct completion c;
 	u32 enabled;
+
+	struct kref consumers;
 };
 
 static DEFINE_MUTEX(transaction_lock);
@@ -225,12 +228,27 @@  static void rpi_register_clk_driver(struct device *dev)
 						-1, NULL, 0);
 }
 
+static void rpi_firmware_delete(struct kref *kref)
+{
+	struct rpi_firmware *fw = container_of(kref, struct rpi_firmware,
+					       consumers);
+
+	mbox_free_channel(fw->chan);
+	kfree(fw);
+}
+
+void rpi_firmware_put(struct rpi_firmware *fw)
+{
+	kref_put(&fw->consumers, rpi_firmware_delete);
+}
+EXPORT_SYMBOL_GPL(rpi_firmware_put);
+
 static int rpi_firmware_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct rpi_firmware *fw;
 
-	fw = devm_kzalloc(dev, sizeof(*fw), GFP_KERNEL);
+	fw = kzalloc(sizeof(*fw), GFP_KERNEL);
 	if (!fw)
 		return -ENOMEM;
 
@@ -247,6 +265,7 @@  static int rpi_firmware_probe(struct platform_device *pdev)
 	}
 
 	init_completion(&fw->c);
+	kref_init(&fw->consumers);
 
 	platform_set_drvdata(pdev, fw);
 
@@ -275,25 +294,35 @@  static int rpi_firmware_remove(struct platform_device *pdev)
 	rpi_hwmon = NULL;
 	platform_device_unregister(rpi_clk);
 	rpi_clk = NULL;
-	mbox_free_channel(fw->chan);
+
+	rpi_firmware_put(fw);
 
 	return 0;
 }
 
 /**
- * rpi_firmware_get - Get pointer to rpi_firmware structure.
  * @firmware_node:    Pointer to the firmware Device Tree node.
  *
+ * The reference to rpi_firmware has to be released with rpi_firmware_put().
+ *
  * Returns NULL is the firmware device is not ready.
  */
 struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
 {
 	struct platform_device *pdev = of_find_device_by_node(firmware_node);
+	struct rpi_firmware *fw;
 
 	if (!pdev)
 		return NULL;
 
-	return platform_get_drvdata(pdev);
+	fw = platform_get_drvdata(pdev);
+	if (!fw)
+		return NULL;
+
+	if (!kref_get_unless_zero(&fw->consumers))
+		return NULL;
+
+	return fw;
 }
 EXPORT_SYMBOL_GPL(rpi_firmware_get);
 
diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
index cc9cdbc66403..fdfef7fe40df 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -140,6 +140,7 @@  int rpi_firmware_property(struct rpi_firmware *fw,
 			  u32 tag, void *data, size_t len);
 int rpi_firmware_property_list(struct rpi_firmware *fw,
 			       void *data, size_t tag_size);
+void rpi_firmware_put(struct rpi_firmware *fw);
 struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node);
 #else
 static inline int rpi_firmware_property(struct rpi_firmware *fw, u32 tag,
@@ -154,6 +155,7 @@  static inline int rpi_firmware_property_list(struct rpi_firmware *fw,
 	return -ENOSYS;
 }
 
+static inline void rpi_firmware_put(struct rpi_firmware *fw) { }
 static inline struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
 {
 	return NULL;