From 23c7b54ca1cd1797ef39169ab85e6d46f1c2d061 Mon Sep 17 00:00:00 2001 From: Enric Balletbo i Serra Date: Wed, 4 Jul 2018 10:45:50 +0200 Subject: 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: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name) Signed-off-by: Enric Balletbo i Serra Reviewed-by: Chanwoo Choi Signed-off-by: MyungJoo Ham --- drivers/devfreq/devfreq.c | 53 +++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 49 insertions(+), 4 deletions(-) (limited to 'drivers/devfreq') diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c index 4c49bb1330b5..62ead442a872 100644 --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -11,6 +11,7 @@ */ #include +#include #include #include #include @@ -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; -- cgit v1.2.3-55-g7522