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PM / devfreq: Fix devfreq_add_device() when drivers are built as modules. 

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: 1b5c1be2c8 (PM / devfreq: map devfreq drivers to governor using name)
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
This commit is contained in:
Enric Balletbo i Serra 2018-07-04 10:45:50 +02:00 committed by MyungJoo Ham
parent 17b57b1883
commit 23c7b54ca1
1 changed files with 49 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
drivers/devfreq/devfreq.c
View File

@ -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 +222,49 @@ 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.
* devfreq_list_lock should be held by the caller. Returns the matched
* governor's pointer.
*/
static struct devfreq_governor *try_then_request_governor(const char *name)
{
struct devfreq_governor *governor;
int err = 0;
if (IS_ERR_OR_NULL(name)) {
pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
return ERR_PTR(-EINVAL);
}
WARN(!mutex_is_locked(&devfreq_list_lock),
"devfreq_list_lock must be locked.");
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);
/* Restore previous state before return */
mutex_lock(&devfreq_list_lock);
if (err)
return NULL;
governor = find_devfreq_governor(name);
}
return governor;
}
static int devfreq_notify_transition(struct devfreq *devfreq,
struct devfreq_freqs *freqs, unsigned int state)
{
@ -646,9 +690,8 @@ 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__);
@ -664,12 +707,14 @@ 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);
device_unregister(&devfreq->dev);
@ -991,7 +1036,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
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;