When the devfreq driver and the governor driver are built as modules,
the call to devfreq_add_device() or governor_store() fails because the
governor driver is not loaded at the time the devfreq driver loads. The
devfreq driver has a build dependency on the governor but also should
have a runtime dependency. We need to make sure that the governor driver
is loaded before the devfreq driver.
This patch fixes this bug by adding a try_then_request_governor()
function. First tries to find the governor, and then, if it is not found,
it requests the module and tries again.
Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
Signed-off-by: Enric Balletbo i Serra <enric.balle...@collabora.com>
---
Changes in v3:
- Remove unneded change in dev_err message.
- Fix err returned value in case to not find the governor.
Changes in v2:
- Add a new function to request the module and call that function from
devfreq_add_device and governor_store.
drivers/devfreq/devfreq.c | 65 ++++++++++++++++++++++++++++++++-------
1 file changed, 54 insertions(+), 11 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0b5b3abe054e..e059c431a558 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -11,6 +11,7 @@
*/
#include <linux/kernel.h>
+#include <linux/kmod.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/err.h>
@@ -221,6 +222,46 @@ static struct devfreq_governor
*find_devfreq_governor(const char *name)
return ERR_PTR(-ENODEV);
}
+/**
+ * try_then_request_governor() - Try to find the governor and request the
+ * module if is not found.
+ * @name: name of the governor
+ *
+ * Search the list of devfreq governors and request the module and try again
+ * if is not found. This can happen when both drivers (the governor driver
+ * and the driver that call devfreq_add_device) are built as modules.
+ *
+ * Return: The matched governor's pointer.
+ */
+static struct devfreq_governor *try_then_request_governor(const char *name)
+{
+ struct devfreq_governor *governor;
+ int err = 0;
+
+ mutex_lock(&devfreq_list_lock);
+
+ governor = find_devfreq_governor(name);
+ if (IS_ERR(governor)) {
+ mutex_unlock(&devfreq_list_lock);
+
+ if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND,
+ DEVFREQ_NAME_LEN))
+ err = request_module("governor_%s", "simpleondemand");
+ else
+ err = request_module("governor_%s", name);
+ if (err)
+ return NULL;
+
+ mutex_lock(&devfreq_list_lock);
+
+ governor = find_devfreq_governor(name);
+ }
+
+ mutex_unlock(&devfreq_list_lock);
+
+ return governor;
+}
+
static int devfreq_notify_transition(struct devfreq *devfreq,
struct devfreq_freqs *freqs, unsigned int state)
{
@@ -644,17 +685,16 @@ struct devfreq *devfreq_add_device(struct device *dev,
mutex_unlock(&devfreq->lock);
- mutex_lock(&devfreq_list_lock);
- list_add(&devfreq->node, &devfreq_list);
-
- governor = find_devfreq_governor(devfreq->governor_name);
+ governor = try_then_request_governor(devfreq->governor_name);
if (IS_ERR(governor)) {
dev_err(dev, "%s: Unable to find governor for the device\n",
__func__);
err = PTR_ERR(governor);
- goto err_init;
+ goto err_unregister;
}
+ mutex_lock(&devfreq_list_lock);
+
devfreq->governor = governor;
err = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_START,
NULL);
@@ -663,14 +703,16 @@ struct devfreq *devfreq_add_device(struct device *dev,
__func__);
goto err_init;
}
+
+ list_add(&devfreq->node, &devfreq_list);
+
mutex_unlock(&devfreq_list_lock);
return devfreq;
err_init:
- list_del(&devfreq->node);
mutex_unlock(&devfreq_list_lock);
-
+err_unregister:
device_unregister(&devfreq->dev);
err_dev:
if (devfreq)
@@ -988,12 +1030,13 @@ static ssize_t governor_store(struct device *dev, struct
device_attribute *attr,
if (ret != 1)
return -EINVAL;
- mutex_lock(&devfreq_list_lock);
- governor = find_devfreq_governor(str_governor);
+ governor = try_then_request_governor(str_governor);
if (IS_ERR(governor)) {
- ret = PTR_ERR(governor);
- goto out;
+ return PTR_ERR(governor);
}
+
+ mutex_lock(&devfreq_list_lock);
+
if (df->governor == governor) {
ret = 0;
goto out;
--
2.17.1
