| Message ID | 1346317203-7357-2-git-send-email-myungjoo.ham@samsung.com (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
On Thursday, August 30, 2012, MyungJoo Ham wrote: > Even if the performance of a device is controlled properly with devfreq, > sometimes, we still need to get PM-QoS inputs in order to meet the > required performance. > > In our testbed of Exynos4412, which has on-chip various DMA devices, the > memory interface and system bus are controlled according to their > utilization by devfreq. However, in some multimedia applications > including video-playing with MFC (multi-function codec) H/W and > photo/video-capturing with FIMC H/W, we have observed issues due to > insufficient DMA throughput or latency. > > In such applications, there are deadlines: less than 16.6ms with 60Hz. > With shorter polling intervals (5 ~ 15ms), the frequencies fluctuate > within a frame and we get missing frames and distorted pictures. > With longer polling intervals (20 ~ 100ms), the response time is not > sufficient and we get distorted or broken images. In other words, > regardless of polling interval, we get poor results with hard-deadline > H/Ws. They, in fact, have a preset requirement on DMA throughput. > > Thus, we need PM-QoS capabilities in devfreq. (Note that for general > user applications, devfreq for bus/memory works fine. They are not so > sensitive to tens of ms in performance increasing responses in general. > > In order to express how to handle QoS requests in devfreq devices, > the devfreq device drivers only need to express the mappings of > QoS value and frequency pairs with QoS class along with > devfreq_add_device() call. > > As a side effect of the implementation, which happens to be positive, > min/max freq is now enforced regardless of governor implementation. Can you please explain in a few words how this is supposed to work in practice? > Tested on Exynos4412 machines with memory/bus frequencies and multimedia > H/W blocks. (camera, video decoding, and video encoding) > > Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> > Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> I'm not entirely convinced yet, but a few comments follow. > --- > Changed from V2-resend > - Removed dependencies on global pm-qos class definitions > - Revised data structure handling pm-qos (being ready for dev-pm-qos) > > Changes from V2 > - Rebased > > Changes from V1 > - Error handling at devfreq_add_device() > - Handling pm_qos_max information > - Styly update > --- > drivers/devfreq/devfreq.c | 127 +++++++++++++++++++++++++++++++++++++++++++-- > include/linux/devfreq.h | 41 ++++++++++++++ > 2 files changed, 164 insertions(+), 4 deletions(-) > > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > index 00e326c..d74b382 100644 > --- a/drivers/devfreq/devfreq.c > +++ b/drivers/devfreq/devfreq.c > @@ -25,6 +25,7 @@ > #include <linux/list.h> > #include <linux/printk.h> > #include <linux/hrtimer.h> > +#include <linux/pm_qos.h> > #include "governor.h" > > static struct class *devfreq_class; > @@ -136,8 +137,13 @@ int update_devfreq(struct devfreq *devfreq) > * List from the highest proiority > * max_freq (probably called by thermal when it's too hot) > * min_freq > + * qos_min_freq > */ > > + if (devfreq->qos_min_freq && freq < devfreq->qos_min_freq) { > + freq = devfreq->qos_min_freq; > + flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */ What exactly is the purpose of this last line? > + } > if (devfreq->min_freq && freq < devfreq->min_freq) { > freq = devfreq->min_freq; > flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */ > @@ -164,12 +170,12 @@ int update_devfreq(struct devfreq *devfreq) > * devfreq_notifier_call() - Notify that the device frequency requirements > * has been changed out of devfreq framework. > * @nb the notifier_block (supposed to be devfreq->nb) > - * @type not used > + * @val not used. > * @devp not used > * > * Called by a notifier that uses devfreq->nb. > */ > -static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type, > +static int devfreq_notifier_call(struct notifier_block *nb, unsigned long val, > void *devp) > { > struct devfreq *devfreq = container_of(nb, struct devfreq, nb); The above change is only a cleanup unrelated to the rest of modifications. Please push it separately (if you _really_ think it's necessary). > @@ -183,6 +189,49 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type, > } > > /** > + * devfreq_qos_notifier_call() - This looks like a missing kerneldoc comment? > + */ > +static int devfreq_qos_notifier_call(struct notifier_block *nb, > + unsigned long value, void *devp) > +{ > + struct devfreq *devfreq = container_of(nb, struct devfreq, qos_nb); > + int ret; > + int i; > + s32 default_value = PM_QOS_DEFAULT_VALUE; > + struct devfreq_pm_qos_table *qos_list = devfreq->profile->qos_list; > + bool qos_use_max = devfreq->profile->qos_use_max; > + > + if (!qos_list) > + return NOTIFY_DONE; > + > + mutex_lock(&devfreq->lock); > + > + if (value == default_value) { > + devfreq->qos_min_freq = 0; > + goto update; > + } > + > + for (i = 0; qos_list[i].freq; i++) { > + /* QoS Met */ > + if ((qos_use_max && qos_list[i].qos_value >= value) || > + (!qos_use_max && qos_list[i].qos_value <= value)) { > + devfreq->qos_min_freq = qos_list[i].freq; > + goto update; > + } What about: if (qos_use_max) { if (qos_list[i].qos_value < value) continue; } else { if (qos_list[i].qos_value > value) continue; } devfreq->qos_min_freq = qos_list[i].freq; goto update; > + } > + > + /* Use the highest QoS freq */ > + if (i > 0) Given the sanity checks in devfreq_add_device(), this is always true. So perhaps you don't even need the "update" label? > + devfreq->qos_min_freq = qos_list[i - 1].freq; > + > +update: > + ret = update_devfreq(devfreq); > + mutex_unlock(&devfreq->lock); > + > + return ret; > +} > + > +/** > * _remove_devfreq() - Remove devfreq from the device. > * @devfreq: the devfreq struct > * @skip: skip calling device_unregister(). > @@ -219,6 +268,10 @@ static void _remove_devfreq(struct devfreq *devfreq, bool skip) > > devfreq->being_removed = true; > > + if (devfreq->profile->qos_type) > + pm_qos_remove_notifier(devfreq->profile->qos_type, > + &devfreq->qos_nb); > + > if (devfreq->profile->exit) > devfreq->profile->exit(devfreq->dev.parent); > > @@ -390,7 +443,7 @@ struct devfreq *devfreq_add_device(struct device *dev, > void *data) > { > struct devfreq *devfreq; > - int err = 0; > + int err = 0, i; > > if (!dev || !profile || !governor) { > dev_err(dev, "%s: Invalid parameters.\n", __func__); > @@ -429,6 +482,61 @@ struct devfreq *devfreq_add_device(struct device *dev, > devfreq->next_polling = devfreq->polling_jiffies > = msecs_to_jiffies(devfreq->profile->polling_ms); > devfreq->nb.notifier_call = devfreq_notifier_call; > + devfreq->qos_nb.notifier_call = devfreq_qos_notifier_call; > + > + /* Check the sanity of qos_list/qos_type */ Any chance to move the sanity checks below to a separate function? > + if (profile->qos_type || profile->qos_list) { > + > + if (WARN(!profile->qos_type || !profile->qos_list, > + "QoS requirement partially omitted for %s.\n", > + dev_name(dev))) { > + > + err = -EINVAL; > + goto err_dev; > + } > + > + if (WARN(!profile->qos_list[0].freq, > + "The first QoS requirement is the end of list for %s.\n", > + dev_name(dev))) { > + > + err = -EINVAL; > + goto err_dev; > + } > + > + for (i = 1; profile->qos_list[i].freq; i++) { > + if (WARN(profile->qos_list[i].freq <= > + profile->qos_list[i - 1].freq, > + "%s's qos_list[].freq not sorted in the ascending order. ([%d]=%lu, [%d]=%lu)\n", > + dev_name(dev), i - 1, > + profile->qos_list[i - 1].freq, i, > + profile->qos_list[i].freq)) { > + > + err = -EINVAL; > + goto err_dev; > + } > + > + /* > + * If QoS type is throughput(PM_QOS_MAX)-like, qos_value > + * should be sorted in the ascending order. > + * If QoS type is latency(PM_QOS_MIN)-like, qos_value > + * should be sorted in the descending order. > + */ > + if (WARN((profile->qos_use_max && > + profile->qos_list[i - 1].qos_value > > + profile->qos_list[i].qos_value) || > + (!profile->qos_use_max && > + profile->qos_list[i - 1].qos_value < > + profile->qos_list[i].qos_value), > + "%s's qos_list[].qos_value is not sorted according to its QoS class.\n", > + dev_name(dev))) { > + > + err = -EINVAL; > + goto err_dev; > + } > + } > + > + pm_qos_add_notifier(profile->qos_type, &devfreq->qos_nb); What QoS types do you think could be used here? > + } > > devfreq->trans_table = devm_kzalloc(dev, sizeof(unsigned int) * > devfreq->profile->max_state * > @@ -443,7 +551,7 @@ struct devfreq *devfreq_add_device(struct device *dev, > err = device_register(&devfreq->dev); > if (err) { > put_device(&devfreq->dev); > - goto err_dev; > + goto err_qos_add; > } > > if (governor->init) > @@ -471,6 +579,9 @@ out: > > err_init: > device_unregister(&devfreq->dev); > +err_qos_add: > + if (profile->qos_type || profile->qos_list) > + pm_qos_remove_notifier(profile->qos_type, &devfreq->qos_nb); > err_dev: > mutex_unlock(&devfreq->lock); > kfree(devfreq); > @@ -568,6 +679,13 @@ static ssize_t show_central_polling(struct device *dev, > !to_devfreq(dev)->governor->no_central_polling); > } > > +static ssize_t show_qos_min_freq(struct device *dev, > + struct device_attribute *attr, > + char *buf) > +{ > + return sprintf(buf, "%lu\n", to_devfreq(dev)->qos_min_freq); > +} > + > static ssize_t store_min_freq(struct device *dev, struct device_attribute *attr, > const char *buf, size_t count) > { > @@ -685,6 +803,7 @@ static struct device_attribute devfreq_attrs[] = { > store_polling_interval), > __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq), > __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq), > + __ATTR(qos_min_freq, S_IRUGO, show_qos_min_freq, NULL), > __ATTR(trans_stat, S_IRUGO, show_trans_table, NULL), > { }, > }; > diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h > index 30dc0d8..d11db17 100644 > --- a/include/linux/devfreq.h > +++ b/include/linux/devfreq.h > @@ -53,6 +53,21 @@ struct devfreq_dev_status { > #define DEVFREQ_FLAG_LEAST_UPPER_BOUND 0x1 > > /** > + * struct devfreq_pm_qos_table - An PM QoS requiement entry for devfreq dev. > + * @freq Lowest frequency to meet the QoS requirement > + * represented by qos_value. If freq=0, it means that > + * this element is the last in the array. > + * @qos_value The qos value defined in pm_qos_params.h pm_qos_params.h doesn't exist any more. pm_qos.h only defines default values, so the meaning of the comment is kind of unclear. > + * > + * Note that the array of devfreq_pm_qos_table should be sorted by freq > + * in the ascending order except for the last element, which should be 0. > + */ > +struct devfreq_pm_qos_table { > + unsigned long freq; /* 0 if this is the last element */ > + s32 qos_value; > +}; I like the idea of translating QoS values into frequencies. However, I don't think it's always possible to figure out how a given global PM QoS value translates into a specific range of frequencies for the given devfreq structure. What method in particular did you use on your test system? > + > +/** > * struct devfreq_dev_profile - Devfreq's user device profile > * @initial_freq The operating frequency when devfreq_add_device() is > * called. > @@ -71,11 +86,33 @@ struct devfreq_dev_status { > * from devfreq_remove_device() call. If the user > * has registered devfreq->nb at a notifier-head, > * this is the time to unregister it. > + * @qos_type QoS Type (defined in pm_qos_params.h) > + * 0 (PM_QOS_RESERVED) if not used. > + * @qos_use_max True: the highest QoS value is used (for QoS > + * requirement of throughput, bandwidth, or similar) > + * False: the lowest QoS value is used (for QoS > + * requirement of latency, delay, or similar) > + * @enable_dev_pm_qos dev_pm_qos is enabled using the qos_list. > + * @qos_list Array of QoS requirements ending with .freq = 0 > + * NULL if not used. It should be either NULL or > + * have a length > 1 with a first element effective. > + * This QoS specification is shared by the global > + * PM QoS (qos_type) and the per-dev PM QoS > + * (enable_dev_pm_qos). > + * > + * Note that the array of qos_list should be sorted by freq > + * in the ascending order. > */ > struct devfreq_dev_profile { > unsigned long initial_freq; > unsigned int polling_ms; > > + /* Optional QoS Handling Specification */ > + int qos_type; /* 0: No global PM-QoS support */ > + bool qos_use_max; /* true if "bandwidth"/"throughput"-like values */ > + bool enable_dev_pm_qos; /* False: No per-dev PM-QoS support */ > + struct devfreq_pm_qos_table *qos_list; /* QoS handling specification */ > + > int (*target)(struct device *dev, unsigned long *freq, u32 flags); > int (*get_dev_status)(struct device *dev, > struct devfreq_dev_status *stat); > @@ -139,6 +176,8 @@ struct devfreq_governor { > * order to prevent trying to remove the object multiple times. > * @min_freq Limit minimum frequency requested by user (0: none) > * @max_freq Limit maximum frequency requested by user (0: none) > + * @qos_nb notifier block used to notify pm qos requests > + * @qos_min_freq Limit minimum frequency requested by QoS > * > * This structure stores the devfreq information for a give device. > * > @@ -167,6 +206,8 @@ struct devfreq { > > unsigned long min_freq; > unsigned long max_freq; > + struct notifier_block qos_nb; > + unsigned long qos_min_freq; > > /* information for device freqeuncy transition */ > unsigned int total_trans; > I think it would be better to fold [2/2] into [1/2] to avoid some unnecessary code churn. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c index 00e326c..d74b382 100644 --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -25,6 +25,7 @@ #include <linux/list.h> #include <linux/printk.h> #include <linux/hrtimer.h> +#include <linux/pm_qos.h> #include "governor.h" static struct class *devfreq_class; @@ -136,8 +137,13 @@ int update_devfreq(struct devfreq *devfreq) * List from the highest proiority * max_freq (probably called by thermal when it's too hot) * min_freq + * qos_min_freq */ + if (devfreq->qos_min_freq && freq < devfreq->qos_min_freq) { + freq = devfreq->qos_min_freq; + flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */ + } if (devfreq->min_freq && freq < devfreq->min_freq) { freq = devfreq->min_freq; flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */ @@ -164,12 +170,12 @@ int update_devfreq(struct devfreq *devfreq) * devfreq_notifier_call() - Notify that the device frequency requirements * has been changed out of devfreq framework. * @nb the notifier_block (supposed to be devfreq->nb) - * @type not used + * @val not used. * @devp not used * * Called by a notifier that uses devfreq->nb. */ -static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type, +static int devfreq_notifier_call(struct notifier_block *nb, unsigned long val, void *devp) { struct devfreq *devfreq = container_of(nb, struct devfreq, nb); @@ -183,6 +189,49 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type, } /** + * devfreq_qos_notifier_call() - + */ +static int devfreq_qos_notifier_call(struct notifier_block *nb, + unsigned long value, void *devp) +{ + struct devfreq *devfreq = container_of(nb, struct devfreq, qos_nb); + int ret; + int i; + s32 default_value = PM_QOS_DEFAULT_VALUE; + struct devfreq_pm_qos_table *qos_list = devfreq->profile->qos_list; + bool qos_use_max = devfreq->profile->qos_use_max; + + if (!qos_list) + return NOTIFY_DONE; + + mutex_lock(&devfreq->lock); + + if (value == default_value) { + devfreq->qos_min_freq = 0; + goto update; + } + + for (i = 0; qos_list[i].freq; i++) { + /* QoS Met */ + if ((qos_use_max && qos_list[i].qos_value >= value) || + (!qos_use_max && qos_list[i].qos_value <= value)) { + devfreq->qos_min_freq = qos_list[i].freq; + goto update; + } + } + + /* Use the highest QoS freq */ + if (i > 0) + devfreq->qos_min_freq = qos_list[i - 1].freq; + +update: + ret = update_devfreq(devfreq); + mutex_unlock(&devfreq->lock); + + return ret; +} + +/** * _remove_devfreq() - Remove devfreq from the device. * @devfreq: the devfreq struct * @skip: skip calling device_unregister(). @@ -219,6 +268,10 @@ static void _remove_devfreq(struct devfreq *devfreq, bool skip) devfreq->being_removed = true; + if (devfreq->profile->qos_type) + pm_qos_remove_notifier(devfreq->profile->qos_type, + &devfreq->qos_nb); + if (devfreq->profile->exit) devfreq->profile->exit(devfreq->dev.parent); @@ -390,7 +443,7 @@ struct devfreq *devfreq_add_device(struct device *dev, void *data) { struct devfreq *devfreq; - int err = 0; + int err = 0, i; if (!dev || !profile || !governor) { dev_err(dev, "%s: Invalid parameters.\n", __func__); @@ -429,6 +482,61 @@ struct devfreq *devfreq_add_device(struct device *dev, devfreq->next_polling = devfreq->polling_jiffies = msecs_to_jiffies(devfreq->profile->polling_ms); devfreq->nb.notifier_call = devfreq_notifier_call; + devfreq->qos_nb.notifier_call = devfreq_qos_notifier_call; + + /* Check the sanity of qos_list/qos_type */ + if (profile->qos_type || profile->qos_list) { + + if (WARN(!profile->qos_type || !profile->qos_list, + "QoS requirement partially omitted for %s.\n", + dev_name(dev))) { + + err = -EINVAL; + goto err_dev; + } + + if (WARN(!profile->qos_list[0].freq, + "The first QoS requirement is the end of list for %s.\n", + dev_name(dev))) { + + err = -EINVAL; + goto err_dev; + } + + for (i = 1; profile->qos_list[i].freq; i++) { + if (WARN(profile->qos_list[i].freq <= + profile->qos_list[i - 1].freq, + "%s's qos_list[].freq not sorted in the ascending order. ([%d]=%lu, [%d]=%lu)\n", + dev_name(dev), i - 1, + profile->qos_list[i - 1].freq, i, + profile->qos_list[i].freq)) { + + err = -EINVAL; + goto err_dev; + } + + /* + * If QoS type is throughput(PM_QOS_MAX)-like, qos_value + * should be sorted in the ascending order. + * If QoS type is latency(PM_QOS_MIN)-like, qos_value + * should be sorted in the descending order. + */ + if (WARN((profile->qos_use_max && + profile->qos_list[i - 1].qos_value > + profile->qos_list[i].qos_value) || + (!profile->qos_use_max && + profile->qos_list[i - 1].qos_value < + profile->qos_list[i].qos_value), + "%s's qos_list[].qos_value is not sorted according to its QoS class.\n", + dev_name(dev))) { + + err = -EINVAL; + goto err_dev; + } + } + + pm_qos_add_notifier(profile->qos_type, &devfreq->qos_nb); + } devfreq->trans_table = devm_kzalloc(dev, sizeof(unsigned int) * devfreq->profile->max_state * @@ -443,7 +551,7 @@ struct devfreq *devfreq_add_device(struct device *dev, err = device_register(&devfreq->dev); if (err) { put_device(&devfreq->dev); - goto err_dev; + goto err_qos_add; } if (governor->init) @@ -471,6 +579,9 @@ out: err_init: device_unregister(&devfreq->dev); +err_qos_add: + if (profile->qos_type || profile->qos_list) + pm_qos_remove_notifier(profile->qos_type, &devfreq->qos_nb); err_dev: mutex_unlock(&devfreq->lock); kfree(devfreq); @@ -568,6 +679,13 @@ static ssize_t show_central_polling(struct device *dev, !to_devfreq(dev)->governor->no_central_polling); } +static ssize_t show_qos_min_freq(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + return sprintf(buf, "%lu\n", to_devfreq(dev)->qos_min_freq); +} + static ssize_t store_min_freq(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { @@ -685,6 +803,7 @@ static struct device_attribute devfreq_attrs[] = { store_polling_interval), __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq), __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq), + __ATTR(qos_min_freq, S_IRUGO, show_qos_min_freq, NULL), __ATTR(trans_stat, S_IRUGO, show_trans_table, NULL), { }, }; diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h index 30dc0d8..d11db17 100644 --- a/include/linux/devfreq.h +++ b/include/linux/devfreq.h @@ -53,6 +53,21 @@ struct devfreq_dev_status { #define DEVFREQ_FLAG_LEAST_UPPER_BOUND 0x1 /** + * struct devfreq_pm_qos_table - An PM QoS requiement entry for devfreq dev. + * @freq Lowest frequency to meet the QoS requirement + * represented by qos_value. If freq=0, it means that + * this element is the last in the array. + * @qos_value The qos value defined in pm_qos_params.h + * + * Note that the array of devfreq_pm_qos_table should be sorted by freq + * in the ascending order except for the last element, which should be 0. + */ +struct devfreq_pm_qos_table { + unsigned long freq; /* 0 if this is the last element */ + s32 qos_value; +}; + +/** * struct devfreq_dev_profile - Devfreq's user device profile * @initial_freq The operating frequency when devfreq_add_device() is * called. @@ -71,11 +86,33 @@ struct devfreq_dev_status { * from devfreq_remove_device() call. If the user * has registered devfreq->nb at a notifier-head, * this is the time to unregister it. + * @qos_type QoS Type (defined in pm_qos_params.h) + * 0 (PM_QOS_RESERVED) if not used. + * @qos_use_max True: the highest QoS value is used (for QoS + * requirement of throughput, bandwidth, or similar) + * False: the lowest QoS value is used (for QoS + * requirement of latency, delay, or similar) + * @enable_dev_pm_qos dev_pm_qos is enabled using the qos_list. + * @qos_list Array of QoS requirements ending with .freq = 0 + * NULL if not used. It should be either NULL or + * have a length > 1 with a first element effective. + * This QoS specification is shared by the global + * PM QoS (qos_type) and the per-dev PM QoS + * (enable_dev_pm_qos). + * + * Note that the array of qos_list should be sorted by freq + * in the ascending order. */ struct devfreq_dev_profile { unsigned long initial_freq; unsigned int polling_ms; + /* Optional QoS Handling Specification */ + int qos_type; /* 0: No global PM-QoS support */ + bool qos_use_max; /* true if "bandwidth"/"throughput"-like values */ + bool enable_dev_pm_qos; /* False: No per-dev PM-QoS support */ + struct devfreq_pm_qos_table *qos_list; /* QoS handling specification */ + int (*target)(struct device *dev, unsigned long *freq, u32 flags); int (*get_dev_status)(struct device *dev, struct devfreq_dev_status *stat); @@ -139,6 +176,8 @@ struct devfreq_governor { * order to prevent trying to remove the object multiple times. * @min_freq Limit minimum frequency requested by user (0: none) * @max_freq Limit maximum frequency requested by user (0: none) + * @qos_nb notifier block used to notify pm qos requests + * @qos_min_freq Limit minimum frequency requested by QoS * * This structure stores the devfreq information for a give device. * @@ -167,6 +206,8 @@ struct devfreq { unsigned long min_freq; unsigned long max_freq; + struct notifier_block qos_nb; + unsigned long qos_min_freq; /* information for device freqeuncy transition */ unsigned int total_trans;