On Mon, Oct 08, 2012 at 07:59:13PM +0900, 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.
>
> 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....@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.p...@samsung.com>
>
> ---
> Changes from V3
> - Corrected and added comments
> - Code Clean
> - Merged per-dev qos patch and global qos patch
>
> 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 | 137
> ++++++++++++++++++++++++++++++++++++++++++++-
> include/linux/devfreq.h | 41 +++++++++++++
> 2 files changed, 177 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 00e326c..d0cb33b 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 */
> @@ -183,6 +189,56 @@ static int devfreq_notifier_call(struct notifier_block
> *nb, unsigned long type,
> }
>
> /**
> + * devfreq_qos_notifier_call() - Handle QoS requests (updates)
> + *
> + * @nb the notifier_block (supposed to be devfreq->qos_nb)
> + * @value the QoS value
> + * @devp not used
> + */
> +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) {
> + 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 */
> + 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 +275,13 @@ static void _remove_devfreq(struct devfreq *devfreq,
> bool skip)
>
> devfreq->being_removed = true;
>
> + if (devfreq->profile->enable_dev_pm_qos)
> + dev_pm_qos_remove_notifier(devfreq->dev.parent,
> + &devfreq->qos_nb);
> + 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);
>
> @@ -376,6 +439,50 @@ static void devfreq_monitor(struct work_struct *work)
> }
> }
>
> +static int devfreq_qos_sanity_check(struct device *dev,
> + struct devfreq_dev_profile *profile)
> +{
> + int i;
> +
> + if (!profile->qos_type && !profile->enable_dev_pm_qos ||
> + !profile->qos_list) {
> + dev_WARN(dev, "QoS requirement partially omitted.");
> + return -EINVAL;
> + }
> +
> + if (!profile->qos_list[0].freq) {
> + dev_WARN(dev, "The first QoS requirement is also the last
> requirement.");
> + return -EINVAL;
> + }
> +
> + for (i = 1; profile->qos_list[i].freq; i++) {
> + if (profile->qos_list[i].freq <=
> + profile->qos_list[i - 1].freq) {
> + dev_WARN(dev, "qos_list[].freq not sorted in the
> ascending order. ([%d]=%lu, [%d]=%lu)\n",
> + i - 1, profile->qos_list[i - 1].freq,
> + i, profile->qos_list[i].freq);
> + return -EINVAL;
> +
> + if (profile->qos_use_max) {
> + /* Throughput-like QoS type */
> + if (profile->qos_list[i - 1].qos_value >
> + profile->qos_list[i].qos_value) {
> + dev_WARN(dev, "qos_list[].qos_value needs to be
> sorted in the ascending order if qos_use_max is true.");
> + return -EINVAL;
> + }
> + } else {
> + /* Latency-like QoS type */
> + if (profile->qos_list[i - 1].qos_value <
> + profile->qos_list[i].qos_value) {
> + dev_WARN(dev, "qos_list[].qos_value needs to be
> sorted in the descending order if qos_use_max is false.");
> + return -EINVAL;
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> /**
> * devfreq_add_device() - Add devfreq feature to the device
> * @dev: the device to add devfreq feature.
> @@ -429,6 +536,21 @@ 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->enable_dev_pm_qos ||
> + profile->qos_list) {
> + err = devfreq_qos_sanity_check(dev, profile);
> + if (err)
> + goto err_dev;
> +
> + if (profile->qos_type)
> + pm_qos_add_notifier(profile->qos_type,
> + &devfreq->qos_nb);
> + if (profile->enable_dev_pm_qos)
> + dev_pm_qos_add_notifier(dev, &devfreq->qos_nb);
> + }
>
> devfreq->trans_table = devm_kzalloc(dev, sizeof(unsigned int) *
> devfreq->profile->max_state *
> @@ -443,7 +565,7 @@ 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 +593,11 @@ out:
>
> err_init:
> device_unregister(&devfreq->dev);
> +err_qos_add:
> + if (profile->enable_dev_pm_qos)
> + dev_pm_qos_remove_notifier(dev, &devfreq->qos_nb);
> + if (profile->qos_type)
> + pm_qos_remove_notifier(profile->qos_type, &devfreq->qos_nb);
> err_dev:
> mutex_unlock(&devfreq->lock);
> kfree(devfreq);
> @@ -568,6 +695,13 @@ 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 +819,7 @@ 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..2488343 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.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.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;
> --
> 1.7.4.1
looks ok to me.
Reviewed-by: mark gross <markgr...@thegnar.org>
--mark
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