[PATCH v5 01/11] firmware: raspberrypi: Keep count of all consumers

Nicolas Saenz Julienne
2020-11-23T18:38:54Z

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);
+ 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