When the devfreq driver and the governor driver are built as modules,
the call to devfreq_add_device() 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 in devfreq_add_device(). First tries to find
the governor, and then, if was 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>
---
drivers/devfreq/devfreq.c | 36 +++++++++++++++++++++++++++++++-----
1 file changed, 31 insertions(+), 5 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index fe2af6aa88fc..1d917f043e30 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>
@@ -648,10 +649,35 @@ struct devfreq *devfreq_add_device(struct device *dev,
governor = find_devfreq_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;
+ list_del(&devfreq->node);
+ mutex_unlock(&devfreq_list_lock);
+
+ /*
+ * If the governor is not found, then request the module and
+ * try again. This can happen when both drivers (the governor
+ * driver and the driver that calls devfreq_add_device) are
+ * built as modules.
+ */
+ if (!strncmp(devfreq->governor_name,
+ DEVFREQ_GOV_SIMPLE_ONDEMAND, DEVFREQ_NAME_LEN))
+ err = request_module("governor_%s", "simpleondemand");
+ else
+ err = request_module("governor_%s",
+ devfreq->governor_name);
+ if (err)
+ goto err_unregister;
+
+ mutex_lock(&devfreq_list_lock);
+ list_add(&devfreq->node, &devfreq_list);
+
+ governor = find_devfreq_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;
+ }
}
devfreq->governor = governor;
@@ -669,7 +695,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
err_init:
list_del(&devfreq->node);
mutex_unlock(&devfreq_list_lock);
-
+err_unregister:
device_unregister(&devfreq->dev);
err_dev:
if (devfreq)
--
2.17.1
