[PATCH v3 01/11] firmware: raspberrypi: Introduce devm_rpi_firmware_get()

Nicolas Saenz Julienne
2020-11-04T10:39:52Z

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);
+
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