Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932356Ab2JJDpc (ORCPT ); Tue, 9 Oct 2012 23:45:32 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:48032 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754286Ab2JJDp3 (ORCPT ); Tue, 9 Oct 2012 23:45:29 -0400 Date: Tue, 9 Oct 2012 20:45:26 -0700 From: mark gross To: MyungJoo Ham Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, rjw@sisk.pl, myungjoo.ham@gmail.com, markgross@thegnar.org, kyungmin.park@samsung.com, khilman@ti.com, jean.pihet@newoldbits.com, mturquette@ti.com, jonghwa3.lee@samsung.com, paul@pwsan.com Subject: Re: [PATCH v4] PM / devfreq: add PM-QoS support Message-ID: <20121010034526.GH21067@MGROSS-X220VM> Reply-To: markgross@thegnar.org References: <1349693953-17826-1-git-send-email-myungjoo.ham@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1349693953-17826-1-git-send-email-myungjoo.ham@samsung.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12910 Lines: 359 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 > Signed-off-by: Kyungmin Park > > --- > 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 > #include > #include > +#include > #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 --mark -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/