[v3,01/11] firmware: raspberrypi: Introduce devm_rpi_firmware_get()
diff mbox series

Message ID 20201104103938.1286-2-nsaenzjulienne@suse.de
State New, archived
Headers show
Series
  • Raspberry Pi PoE HAT fan support
Related show

Commit Message

Nicolas Saenz Julienne Nov. 4, 2020, 10:39 a.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
devm_rpi_firmware_get() which will 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 v2:
 - Create devm_rpi_firmware_get()

 drivers/firmware/raspberrypi.c             | 46 ++++++++++++++++++++++
 include/soc/bcm2835/raspberrypi-firmware.h |  8 ++++
 2 files changed, 54 insertions(+)

Comments

Bartosz Golaszewski Nov. 5, 2020, 9:13 a.m. UTC | #1
On Wed, Nov 4, 2020 at 11:39 AM 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
> devm_rpi_firmware_get() which will 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 v2:
>  - Create devm_rpi_firmware_get()
>
>  drivers/firmware/raspberrypi.c             | 46 ++++++++++++++++++++++
>  include/soc/bcm2835/raspberrypi-firmware.h |  8 ++++
>  2 files changed, 54 insertions(+)
>
> diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
> index 2371d08bdd17..74bdb3bde9dc 100644
> --- a/drivers/firmware/raspberrypi.c
> +++ b/drivers/firmware/raspberrypi.c
> @@ -11,7 +11,9 @@
>  #include <linux/module.h>
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
> +#include <linux/refcount.h>
>  #include <linux/slab.h>
> +#include <linux/wait.h>
>  #include <soc/bcm2835/raspberrypi-firmware.h>
>
>  #define MBOX_MSG(chan, data28)         (((data28) & ~0xf) | ((chan) & 0xf))
> @@ -27,6 +29,9 @@ struct rpi_firmware {
>         struct mbox_chan *chan; /* The property channel. */
>         struct completion c;
>         u32 enabled;
> +
> +       refcount_t consumers;
> +       wait_queue_head_t wait;
>  };
>
>  static DEFINE_MUTEX(transaction_lock);
> @@ -247,6 +252,8 @@ static int rpi_firmware_probe(struct platform_device *pdev)
>         }
>
>         init_completion(&fw->c);
> +       refcount_set(&fw->consumers, 1);
> +       init_waitqueue_head(&fw->wait);
>
>         platform_set_drvdata(pdev, fw);
>
> @@ -275,11 +282,21 @@ static int rpi_firmware_remove(struct platform_device *pdev)
>         rpi_hwmon = NULL;
>         platform_device_unregister(rpi_clk);
>         rpi_clk = NULL;
> +
> +       wait_event(fw->wait, refcount_dec_if_one(&fw->consumers));
>         mbox_free_channel(fw->chan);
>
>         return 0;
>  }
>
> +static void rpi_firmware_put(void *data)
> +{
> +       struct rpi_firmware *fw = data;
> +
> +       refcount_dec(&fw->consumers);
> +       wake_up(&fw->wait);
> +}
> +
>  /**
>   * rpi_firmware_get - Get pointer to rpi_firmware structure.
>   * @firmware_node:    Pointer to the firmware Device Tree node.
> @@ -297,6 +314,35 @@ struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
>  }
>  EXPORT_SYMBOL_GPL(rpi_firmware_get);
>
> +/**
> + * devm_rpi_firmware_get - Get pointer to rpi_firmware structure.
> + * @firmware_node:    Pointer to the firmware Device Tree node.
> + *
> + * Returns NULL is the firmware device is not ready.
> + */
> +struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
> +                                          struct device_node *firmware_node)
> +{
> +       struct platform_device *pdev = of_find_device_by_node(firmware_node);
> +       struct rpi_firmware *fw;
> +
> +       if (!pdev)
> +               return NULL;
> +
> +       fw = platform_get_drvdata(pdev);
> +       if (!fw)
> +               return NULL;
> +
> +       if (!refcount_inc_not_zero(&fw->consumers))
> +               return NULL;
> +
> +       if (devm_add_action_or_reset(dev, rpi_firmware_put, fw))
> +               return NULL;
> +
> +       return fw;
> +}
> +EXPORT_SYMBOL_GPL(devm_rpi_firmware_get);

Usually I'd expect the devres variant to simply call
rpi_firmware_get() and then schedule a release callback which would
call whatever function is the release counterpart for it currently.
Devres actions are for drivers which want to schedule some more
unusual tasks at driver detach. Any reason for designing it this way?

Bartosz

> +
>  static const struct of_device_id rpi_firmware_of_match[] = {
>         { .compatible = "raspberrypi,bcm2835-firmware", },
>         {},
> diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
> index cc9cdbc66403..8fe64f53a394 100644
> --- a/include/soc/bcm2835/raspberrypi-firmware.h
> +++ b/include/soc/bcm2835/raspberrypi-firmware.h
> @@ -141,6 +141,8 @@ int rpi_firmware_property(struct rpi_firmware *fw,
>  int rpi_firmware_property_list(struct rpi_firmware *fw,
>                                void *data, size_t tag_size);
>  struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node);
> +struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
> +                                          struct device_node *firmware_node);
>  #else
>  static inline int rpi_firmware_property(struct rpi_firmware *fw, u32 tag,
>                                         void *data, size_t len)
> @@ -158,6 +160,12 @@ static inline struct rpi_firmware *rpi_firmware_get(struct device_node *firmware
>  {
>         return NULL;
>  }
> +
> +static inline struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
> +                                       struct device_node *firmware_node)
> +{
> +       return NULL;
> +}
>  #endif
>
>  #endif /* __SOC_RASPBERRY_FIRMWARE_H__ */
> --
> 2.29.1
>
Nicolas Saenz Julienne Nov. 5, 2020, 9:28 a.m. UTC | #2
Hi Bartosz, thanks for the review.

On Thu, 2020-11-05 at 10:13 +0100, Bartosz Golaszewski wrote:
> > +/**
> > + * devm_rpi_firmware_get - Get pointer to rpi_firmware structure.
> > + * @firmware_node:    Pointer to the firmware Device Tree node.
> > + *
> > + * Returns NULL is the firmware device is not ready.
> > + */
> > +struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
> > +                                          struct device_node *firmware_node)
> > +{
> > +       struct platform_device *pdev = of_find_device_by_node(firmware_node);
> > +       struct rpi_firmware *fw;
> > +
> > +       if (!pdev)
> > +               return NULL;
> > +
> > +       fw = platform_get_drvdata(pdev);
> > +       if (!fw)
> > +               return NULL;
> > +
> > +       if (!refcount_inc_not_zero(&fw->consumers))
> > +               return NULL;
> > +
> > +       if (devm_add_action_or_reset(dev, rpi_firmware_put, fw))
> > +               return NULL;
> > +
> > +       return fw;
> > +}
> > +EXPORT_SYMBOL_GPL(devm_rpi_firmware_get);
> 
> Usually I'd expect the devres variant to simply call
> rpi_firmware_get() and then schedule a release callback which would
> call whatever function is the release counterpart for it currently.
> Devres actions are for drivers which want to schedule some more
> unusual tasks at driver detach. Any reason for designing it this way?

Yes, see patch #8 where I get rid of rpi_firmware_get() altogether after
converting all users to devres. Since there is no use for the vanilla version
of the function anymore, I figured it'd be better to merge everything into
devm_rpi_firmware_get(). That said it's not something I have strong feelings
about.

Regards,
Nicolas
Bartosz Golaszewski Nov. 5, 2020, 9:42 a.m. UTC | #3
On Thu, Nov 5, 2020 at 10:28 AM Nicolas Saenz Julienne
<nsaenzjulienne@suse.de> wrote:
>
> Hi Bartosz, thanks for the review.
>
> On Thu, 2020-11-05 at 10:13 +0100, Bartosz Golaszewski wrote:
> > > +/**
> > > + * devm_rpi_firmware_get - Get pointer to rpi_firmware structure.
> > > + * @firmware_node:    Pointer to the firmware Device Tree node.
> > > + *
> > > + * Returns NULL is the firmware device is not ready.
> > > + */
> > > +struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
> > > +                                          struct device_node *firmware_node)
> > > +{
> > > +       struct platform_device *pdev = of_find_device_by_node(firmware_node);
> > > +       struct rpi_firmware *fw;
> > > +
> > > +       if (!pdev)
> > > +               return NULL;
> > > +
> > > +       fw = platform_get_drvdata(pdev);
> > > +       if (!fw)
> > > +               return NULL;
> > > +
> > > +       if (!refcount_inc_not_zero(&fw->consumers))
> > > +               return NULL;
> > > +
> > > +       if (devm_add_action_or_reset(dev, rpi_firmware_put, fw))
> > > +               return NULL;
> > > +
> > > +       return fw;
> > > +}
> > > +EXPORT_SYMBOL_GPL(devm_rpi_firmware_get);
> >
> > Usually I'd expect the devres variant to simply call
> > rpi_firmware_get() and then schedule a release callback which would
> > call whatever function is the release counterpart for it currently.
> > Devres actions are for drivers which want to schedule some more
> > unusual tasks at driver detach. Any reason for designing it this way?
>
> Yes, see patch #8 where I get rid of rpi_firmware_get() altogether after
> converting all users to devres. Since there is no use for the vanilla version
> of the function anymore, I figured it'd be better to merge everything into
> devm_rpi_firmware_get(). That said it's not something I have strong feelings
> about.
>

I see. So the previous version didn't really have any reference
counting and it leaked the reference returned by
of_find_device_by_node(), got it. Could you just clarify for me the
logic behind the wait_queue in rpi_firmware_remove()? If the firmware
driver gets detached and remove() stops on the wait_queue - it will be
stuck until the last user releases the firmware. I'm not sure this is
correct. I'd prefer to see a kref with a release callback and remove
would simply decrease the kref and return. Each user would do the same
and then after the last user is detached the firmware would be
destroyed.

Don't we really have some centralized firmware subsystem that would handle this?

Bartosz
Nicolas Saenz Julienne Nov. 10, 2020, 1:38 p.m. UTC | #4
Hi Bartosz, thanks for the feedback.

On Thu, 2020-11-05 at 10:42 +0100, Bartosz Golaszewski wrote:
> On Thu, Nov 5, 2020 at 10:28 AM Nicolas Saenz Julienne
> <nsaenzjulienne@suse.de> wrote:
> > Hi Bartosz, thanks for the review.
> > 
> > On Thu, 2020-11-05 at 10:13 +0100, Bartosz Golaszewski wrote:
> > > > +/**
> > > > + * devm_rpi_firmware_get - Get pointer to rpi_firmware structure.
> > > > + * @firmware_node:    Pointer to the firmware Device Tree node.
> > > > + *
> > > > + * Returns NULL is the firmware device is not ready.
> > > > + */
> > > > +struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
> > > > +                                          struct device_node *firmware_node)
> > > > +{
> > > > +       struct platform_device *pdev = of_find_device_by_node(firmware_node);
> > > > +       struct rpi_firmware *fw;
> > > > +
> > > > +       if (!pdev)
> > > > +               return NULL;
> > > > +
> > > > +       fw = platform_get_drvdata(pdev);
> > > > +       if (!fw)
> > > > +               return NULL;
> > > > +
> > > > +       if (!refcount_inc_not_zero(&fw->consumers))
> > > > +               return NULL;
> > > > +
> > > > +       if (devm_add_action_or_reset(dev, rpi_firmware_put, fw))
> > > > +               return NULL;
> > > > +
> > > > +       return fw;
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(devm_rpi_firmware_get);
> > > 
> > > Usually I'd expect the devres variant to simply call
> > > rpi_firmware_get() and then schedule a release callback which would
> > > call whatever function is the release counterpart for it currently.
> > > Devres actions are for drivers which want to schedule some more
> > > unusual tasks at driver detach. Any reason for designing it this way?
> > 
> > Yes, see patch #8 where I get rid of rpi_firmware_get() altogether after
> > converting all users to devres. Since there is no use for the vanilla version
> > of the function anymore, I figured it'd be better to merge everything into
> > devm_rpi_firmware_get(). That said it's not something I have strong feelings
> > about.
> > 
> 
> I see. So the previous version didn't really have any reference
> counting and it leaked the reference returned by
> of_find_device_by_node(), got it. Could you just clarify for me the
> logic behind the wait_queue in rpi_firmware_remove()? If the firmware
> driver gets detached and remove() stops on the wait_queue - it will be
> stuck until the last user releases the firmware. I'm not sure this is
> correct.

Yes, that's what I meant to implement.

> I'd prefer to see a kref with a release callback and remove
> would simply decrease the kref and return. Each user would do the same
> and then after the last user is detached the firmware would be
> destroyed.

Sounds good to me. I'll update it.

> Don't we really have some centralized firmware subsystem that would handle this?

Sadly no, this is an RPi specific thing, it doesn't live behind a standard like
other firmware based protocols (for ex. SCMI), and evolves as the needs arise.

Regards,
Nicolas

Patch
diff mbox series

diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
index 2371d08bdd17..74bdb3bde9dc 100644
--- a/drivers/firmware/raspberrypi.c
+++ b/drivers/firmware/raspberrypi.c
@@ -11,7 +11,9 @@ 
 #include <linux/module.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
+#include <linux/wait.h>
 #include <soc/bcm2835/raspberrypi-firmware.h>
 
 #define MBOX_MSG(chan, data28)		(((data28) & ~0xf) | ((chan) & 0xf))
@@ -27,6 +29,9 @@  struct rpi_firmware {
 	struct mbox_chan *chan; /* The property channel. */
 	struct completion c;
 	u32 enabled;
+
+	refcount_t consumers;
+	wait_queue_head_t wait;
 };
 
 static DEFINE_MUTEX(transaction_lock);
@@ -247,6 +252,8 @@  static int rpi_firmware_probe(struct platform_device *pdev)
 	}
 
 	init_completion(&fw->c);
+	refcount_set(&fw->consumers, 1);
+	init_waitqueue_head(&fw->wait);
 
 	platform_set_drvdata(pdev, fw);
 
@@ -275,11 +282,21 @@  static int rpi_firmware_remove(struct platform_device *pdev)
 	rpi_hwmon = NULL;
 	platform_device_unregister(rpi_clk);
 	rpi_clk = NULL;
+
+	wait_event(fw->wait, refcount_dec_if_one(&fw->consumers));
 	mbox_free_channel(fw->chan);
 
 	return 0;
 }
 
+static void rpi_firmware_put(void *data)
+{
+	struct rpi_firmware *fw = data;
+
+	refcount_dec(&fw->consumers);
+	wake_up(&fw->wait);
+}
+
 /**
  * rpi_firmware_get - Get pointer to rpi_firmware structure.
  * @firmware_node:    Pointer to the firmware Device Tree node.
@@ -297,6 +314,35 @@  struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
 }
 EXPORT_SYMBOL_GPL(rpi_firmware_get);
 
+/**
+ * devm_rpi_firmware_get - Get pointer to rpi_firmware structure.
+ * @firmware_node:    Pointer to the firmware Device Tree node.
+ *
+ * Returns NULL is the firmware device is not ready.
+ */
+struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
+					   struct device_node *firmware_node)
+{
+	struct platform_device *pdev = of_find_device_by_node(firmware_node);
+	struct rpi_firmware *fw;
+
+	if (!pdev)
+		return NULL;
+
+	fw = platform_get_drvdata(pdev);
+	if (!fw)
+		return NULL;
+
+	if (!refcount_inc_not_zero(&fw->consumers))
+		return NULL;
+
+	if (devm_add_action_or_reset(dev, rpi_firmware_put, fw))
+		return NULL;
+
+	return fw;
+}
+EXPORT_SYMBOL_GPL(devm_rpi_firmware_get);
+
 static const struct of_device_id rpi_firmware_of_match[] = {
 	{ .compatible = "raspberrypi,bcm2835-firmware", },
 	{},
diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
index cc9cdbc66403..8fe64f53a394 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -141,6 +141,8 @@  int rpi_firmware_property(struct rpi_firmware *fw,
 int rpi_firmware_property_list(struct rpi_firmware *fw,
 			       void *data, size_t tag_size);
 struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node);
+struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
+					   struct device_node *firmware_node);
 #else
 static inline int rpi_firmware_property(struct rpi_firmware *fw, u32 tag,
 					void *data, size_t len)
@@ -158,6 +160,12 @@  static inline struct rpi_firmware *rpi_firmware_get(struct device_node *firmware
 {
 	return NULL;
 }
+
+static inline struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
+					struct device_node *firmware_node)
+{
+	return NULL;
+}
 #endif
 
 #endif /* __SOC_RASPBERRY_FIRMWARE_H__ */