Commit 23c7b54c authored by Enric Balletbo i Serra's avatar Enric Balletbo i Serra Committed by MyungJoo Ham
Browse files

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: 1b5c1be2 (PM / devfreq: map devfreq drivers to governor using name)
Signed-off-by: default avatarEnric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: default avatarChanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: default avatarMyungJoo Ham <myungjoo.ham@samsung.com>
parent 17b57b18

drivers/devfreq/devfreq.c

+49 −4
Original line number Diff line number Diff line
@@ -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;

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