* [PATCH] PM / devfreq: add PM QoS support
@ 2012-02-10 7:19 MyungJoo Ham
2012-02-28 5:46 ` [PATCH v2] " MyungJoo Ham
0 siblings, 1 reply; 6+ messages in thread
From: MyungJoo Ham @ 2012-02-10 7:19 UTC (permalink / raw
To: linux-kernel, linux-pm
Cc: Kyungmin Park, Rafael J. Wysocki, Kevin Hilman, Mike Turquette,
myungjoo.ham
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.
Tested on Exynos4412 machines with memory/bus frequencies and multimedia
H/W blocks. (camera, video decoding, and video encoding) Also tested on
display-related block's frequencies. (but, this driver is not yet
upstreamed.:) )
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
drivers/devfreq/devfreq.c | 162 ++++++++++++++++++++++++++++++++++++++++++++-
include/linux/devfreq.h | 37 ++++++++++
2 files changed, 196 insertions(+), 3 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a129a7b..a33fc6c 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"
struct class *devfreq_class;
@@ -94,6 +95,26 @@ int update_devfreq(struct devfreq *devfreq)
if (err)
return err;
+ /*
+ * Adjust the freuqency with user freq and QoS.
+ *
+ * List from the highest proiority
+ * min_freq
+ * max_freq
+ * qos_min_freq
+ */
+
+ if (devfreq->qos_min_freq && freq < devfreq->qos_min_freq)
+ freq = devfreq->qos_min_freq;
+ if (devfreq->max_freq && freq > devfreq->max_freq)
+ freq = devfreq->max_freq;
+ if (devfreq->min_freq && freq < devfreq->min_freq)
+ freq = devfreq->min_freq;
+
+ /*
+ * TODO in the devfreq-next:
+ * add relation or use rance (freq_min, freq_max)
+ */
err = devfreq->profile->target(devfreq->dev.parent, &freq);
if (err)
return err;
@@ -106,12 +127,12 @@ 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);
@@ -125,6 +146,49 @@ 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().
@@ -371,12 +435,78 @@ 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) {
+ int i;
+ bool positive_corelation = false;
+
+ if (profile->qos_type == PM_QOS_CPU_DMA_LATENCY ||
+ profile->qos_type == PM_QOS_NETWORK_LATENCY) {
+ if (profile->qos_use_max) {
+ dev_err(dev, "qos_use_max value inconsistent\n");
+ err = -EINVAL;
+ }
+ } else {
+ if (!profile->qos_use_max) {
+ dev_err(dev, "qos_use_max value inconsistent\n");
+ err = -EINVAL;
+ }
+ }
+ if (err)
+ goto err_dev;
+
+ if (!profile->qos_type || !profile->qos_list) {
+ dev_err(dev, "QoS requirement partially omitted.\n");
+ err = -EINVAL;
+ goto err_dev;
+ }
+
+ if (!profile->qos_list[0].freq) {
+ dev_err(dev, "The first QoS requirement is the end of list.\n");
+ err = -EINVAL;
+ goto err_dev;
+ }
+
+ for (i = 1; profile->qos_list[i].freq; i++) {
+ if (profile->qos_list[i].freq <=
+ profile->qos_list[i - 1].freq) {
+ dev_err(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);
+ err = -EINVAL;
+ goto err_dev;
+ }
+
+ if (i == 1) {
+ if (profile->qos_list[0].qos_value <
+ profile->qos_list[1].qos_value)
+ positive_corelation = true;
+ continue;
+ }
+
+ if (((profile->qos_list[i - 1].qos_value <=
+ profile->qos_list[i].qos_value) &&
+ !positive_corelation)
+ ||
+ ((profile->qos_list[i - 1].qos_value >=
+ profile->qos_list[i].qos_value) &&
+ positive_corelation)) {
+ dev_err(dev, "qos_list[].qos_value not sorted.\n");
+ err = -EINVAL;
+ goto err_dev;
+ }
+ }
+
+ pm_qos_add_notifier(profile->qos_type, &devfreq->qos_nb);
+ }
dev_set_name(&devfreq->dev, dev_name(dev));
err = device_register(&devfreq->dev);
if (err) {
put_device(&devfreq->dev);
- goto err_dev;
+ goto err_qos_add;
}
if (governor->init)
@@ -404,6 +534,9 @@ 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);
@@ -434,6 +567,11 @@ int devfreq_remove_device(struct devfreq *devfreq)
}
mutex_lock(&devfreq->lock);
+
+ if (devfreq->profile->qos_type)
+ pm_qos_remove_notifier(devfreq->profile->qos_type,
+ &devfreq->qos_nb);
+
_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
if (central_polling)
@@ -501,6 +639,13 @@ 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)
{
@@ -577,6 +722,7 @@ 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),
{ },
};
@@ -671,6 +817,16 @@ int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
return srcu_notifier_chain_unregister(nh, &devfreq->nb);
}
+/**
+ * In progress (prototyping)
+ */
+int devfreq_simple_ondemand_flexrate_do(struct devfreq *devfreq,
+ unsigned long interval,
+ unsigned long number)
+{
+ return 0;
+}
+
MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
MODULE_DESCRIPTION("devfreq class support");
MODULE_LICENSE("GPL");
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 5862475..b853379 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -45,10 +45,32 @@ struct devfreq_dev_status {
};
/**
+ * 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.
* @polling_ms The polling interval in ms. 0 disables polling.
+ * @qos_type QoS Type (defined in pm_qos_params.h)
+ * 0 (PM_QOS_RESERVED) if not used.
+ * @qos_use_max true: throughput (larger is faster)
+ * false: latency (smaller is faster)
+ * @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.
* @target The device should set its operating frequency at
* freq or lowest-upper-than-freq value. If freq is
* higher than any operable frequency, set maximum.
@@ -61,11 +83,18 @@ 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.
+ *
+ * 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;
+ int qos_type;
+ bool qos_use_max;
+ struct devfreq_pm_qos_table *qos_list;
+
int (*target)(struct device *dev, unsigned long *freq);
int (*get_dev_status)(struct device *dev,
struct devfreq_dev_status *stat);
@@ -126,6 +155,8 @@ 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.
*
@@ -154,6 +185,8 @@ struct devfreq {
unsigned long min_freq;
unsigned long max_freq;
+ struct notifier_block qos_nb;
+ unsigned long qos_min_freq;
};
#if defined(CONFIG_PM_DEVFREQ)
@@ -199,6 +232,10 @@ struct devfreq_simple_ondemand_data {
unsigned int upthreshold;
unsigned int downdifferential;
};
+
+int devfreq_simple_ondemand_flexrate_do(struct devfreq *devfreq,
+ unsigned long interval,
+ unsigned long number);
#endif
#else /* !CONFIG_PM_DEVFREQ */
--
1.7.4.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v2] PM / devfreq: add PM QoS support
2012-02-10 7:19 [PATCH] PM / devfreq: add PM QoS support MyungJoo Ham
@ 2012-02-28 5:46 ` MyungJoo Ham
2012-02-29 9:43 ` [PATCH v2 RESEND] " MyungJoo Ham
0 siblings, 1 reply; 6+ messages in thread
From: MyungJoo Ham @ 2012-02-28 5:46 UTC (permalink / raw
To: linux-kernel, linux-pm
Cc: Kyungmin Park, Rafael J. Wysocki, Kevin Hilman, Mike Turquette,
mark gross, myungjoo.ham
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.
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>
---
Changes from V1
- (style update) Error handling at devfreq_add_device()
- (style update) Handling pm_qos_max information
---
drivers/devfreq/devfreq.c | 166 +++++++++++++++++++++++++++++++++++++++++++-
include/linux/devfreq.h | 37 ++++++++++
2 files changed, 199 insertions(+), 4 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a129a7b..0b49f59 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"
struct class *devfreq_class;
@@ -94,6 +95,26 @@ int update_devfreq(struct devfreq *devfreq)
if (err)
return err;
+ /*
+ * Adjust the freuqency with user freq and QoS.
+ *
+ * List from the highest proiority
+ * min_freq
+ * max_freq
+ * qos_min_freq
+ */
+
+ if (devfreq->qos_min_freq && freq < devfreq->qos_min_freq)
+ freq = devfreq->qos_min_freq;
+ if (devfreq->max_freq && freq > devfreq->max_freq)
+ freq = devfreq->max_freq;
+ if (devfreq->min_freq && freq < devfreq->min_freq)
+ freq = devfreq->min_freq;
+
+ /*
+ * TODO in the devfreq-next:
+ * add relation or use rance (freq_min, freq_max)
+ */
err = devfreq->profile->target(devfreq->dev.parent, &freq);
if (err)
return err;
@@ -106,12 +127,12 @@ 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);
@@ -125,6 +146,49 @@ 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->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().
@@ -332,7 +396,7 @@ 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__);
@@ -371,12 +435,80 @@ 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) {
+ switch (profile->qos_type) {
+ case PM_QOS_CPU_DMA_LATENCY:
+ case PM_QOS_NETWORK_LATENCY:
+ devfreq->qos_use_max = false;
+ break;
+ case PM_QOS_NETWORK_THROUGHPUT:
+ devfreq->qos_use_max = true;
+ break;
+ default:
+ WARN(true, "Unknown PM-QoS Class (%d).\n", profile->qos_type);
+ err = -EINVAL;
+ goto err_dev;
+ }
+
+ 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), qos_value
+ * should be sorted in the ascending order.
+ * If QoS type is latency(PM_QOS_MIN), qos_value
+ * should be sorted in the descending order.
+ */
+ if (WARN((devfreq->qos_use_max &&
+ profile->qos_list[i - 1].qos_value >
+ profile->qos_list[i].qos_value) ||
+ (!devfreq->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);
+ }
dev_set_name(&devfreq->dev, dev_name(dev));
err = device_register(&devfreq->dev);
if (err) {
put_device(&devfreq->dev);
- goto err_dev;
+ goto err_qos_add;
}
if (governor->init)
@@ -404,6 +536,9 @@ 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);
@@ -434,6 +569,11 @@ int devfreq_remove_device(struct devfreq *devfreq)
}
mutex_lock(&devfreq->lock);
+
+ if (devfreq->profile->qos_type)
+ pm_qos_remove_notifier(devfreq->profile->qos_type,
+ &devfreq->qos_nb);
+
_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
if (central_polling)
@@ -501,6 +641,13 @@ 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)
{
@@ -577,6 +724,7 @@ 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),
{ },
};
@@ -671,6 +819,16 @@ int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
return srcu_notifier_chain_unregister(nh, &devfreq->nb);
}
+/**
+ * In progress (prototyping)
+ */
+int devfreq_simple_ondemand_flexrate_do(struct devfreq *devfreq,
+ unsigned long interval,
+ unsigned long number)
+{
+ return 0;
+}
+
MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
MODULE_DESCRIPTION("devfreq class support");
MODULE_LICENSE("GPL");
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 5862475..f27d511 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -45,10 +45,30 @@ struct devfreq_dev_status {
};
/**
+ * 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.
* @polling_ms The polling interval in ms. 0 disables polling.
+ * @qos_type QoS Type (defined in pm_qos_params.h)
+ * 0 (PM_QOS_RESERVED) if not used.
+ * @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.
* @target The device should set its operating frequency at
* freq or lowest-upper-than-freq value. If freq is
* higher than any operable frequency, set maximum.
@@ -61,11 +81,17 @@ 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.
+ *
+ * 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;
+ int qos_type;
+ struct devfreq_pm_qos_table *qos_list;
+
int (*target)(struct device *dev, unsigned long *freq);
int (*get_dev_status)(struct device *dev,
struct devfreq_dev_status *stat);
@@ -126,6 +152,10 @@ 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
+ * @qos_use_max true: throughput (larger is faster)
+ * false: latency (smaller is faster)
*
* This structure stores the devfreq information for a give device.
*
@@ -154,6 +184,9 @@ struct devfreq {
unsigned long min_freq;
unsigned long max_freq;
+ struct notifier_block qos_nb;
+ unsigned long qos_min_freq;
+ bool qos_use_max;
};
#if defined(CONFIG_PM_DEVFREQ)
@@ -199,6 +232,10 @@ struct devfreq_simple_ondemand_data {
unsigned int upthreshold;
unsigned int downdifferential;
};
+
+int devfreq_simple_ondemand_flexrate_do(struct devfreq *devfreq,
+ unsigned long interval,
+ unsigned long number);
#endif
#else /* !CONFIG_PM_DEVFREQ */
--
1.7.4.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v2 RESEND] PM / devfreq: add PM QoS support
2012-02-28 5:46 ` [PATCH v2] " MyungJoo Ham
@ 2012-02-29 9:43 ` MyungJoo Ham
2012-02-29 22:19 ` Turquette, Mike
0 siblings, 1 reply; 6+ messages in thread
From: MyungJoo Ham @ 2012-02-29 9:43 UTC (permalink / raw
To: linux-kernel, linux-pm
Cc: Kyungmin Park, Rafael J. Wysocki, Kevin Hilman, Mike Turquette,
mark gross, myungjoo.ham
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.
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>
---
Changes from V2 (at V2 resend)
- Removed accidently inserted prototype code.
Changes from V1
- Error handling at devfreq_add_device()
- Handling pm_qos_max information
- Styly update
---
drivers/devfreq/devfreq.c | 156 +++++++++++++++++++++++++++++++++++++++++++-
include/linux/devfreq.h | 33 ++++++++++
2 files changed, 185 insertions(+), 4 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a129a7b..f5630f3 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"
struct class *devfreq_class;
@@ -94,6 +95,26 @@ int update_devfreq(struct devfreq *devfreq)
if (err)
return err;
+ /*
+ * Adjust the freuqency with user freq and QoS.
+ *
+ * List from the highest proiority
+ * min_freq
+ * max_freq
+ * qos_min_freq
+ */
+
+ if (devfreq->qos_min_freq && freq < devfreq->qos_min_freq)
+ freq = devfreq->qos_min_freq;
+ if (devfreq->max_freq && freq > devfreq->max_freq)
+ freq = devfreq->max_freq;
+ if (devfreq->min_freq && freq < devfreq->min_freq)
+ freq = devfreq->min_freq;
+
+ /*
+ * TODO in the devfreq-next:
+ * add relation or use rance (freq_min, freq_max)
+ */
err = devfreq->profile->target(devfreq->dev.parent, &freq);
if (err)
return err;
@@ -106,12 +127,12 @@ 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);
@@ -125,6 +146,49 @@ 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->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().
@@ -332,7 +396,7 @@ 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__);
@@ -371,12 +435,80 @@ 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) {
+ switch (profile->qos_type) {
+ case PM_QOS_CPU_DMA_LATENCY:
+ case PM_QOS_NETWORK_LATENCY:
+ devfreq->qos_use_max = false;
+ break;
+ case PM_QOS_NETWORK_THROUGHPUT:
+ devfreq->qos_use_max = true;
+ break;
+ default:
+ WARN(true, "Unknown PM-QoS Class (%d).\n", profile->qos_type);
+ err = -EINVAL;
+ goto err_dev;
+ }
+
+ 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), qos_value
+ * should be sorted in the ascending order.
+ * If QoS type is latency(PM_QOS_MIN), qos_value
+ * should be sorted in the descending order.
+ */
+ if (WARN((devfreq->qos_use_max &&
+ profile->qos_list[i - 1].qos_value >
+ profile->qos_list[i].qos_value) ||
+ (!devfreq->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);
+ }
dev_set_name(&devfreq->dev, dev_name(dev));
err = device_register(&devfreq->dev);
if (err) {
put_device(&devfreq->dev);
- goto err_dev;
+ goto err_qos_add;
}
if (governor->init)
@@ -404,6 +536,9 @@ 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);
@@ -434,6 +569,11 @@ int devfreq_remove_device(struct devfreq *devfreq)
}
mutex_lock(&devfreq->lock);
+
+ if (devfreq->profile->qos_type)
+ pm_qos_remove_notifier(devfreq->profile->qos_type,
+ &devfreq->qos_nb);
+
_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
if (central_polling)
@@ -501,6 +641,13 @@ 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)
{
@@ -577,6 +724,7 @@ 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),
{ },
};
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 5862475..dbc6cea 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -45,10 +45,30 @@ struct devfreq_dev_status {
};
/**
+ * 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.
* @polling_ms The polling interval in ms. 0 disables polling.
+ * @qos_type QoS Type (defined in pm_qos_params.h)
+ * 0 (PM_QOS_RESERVED) if not used.
+ * @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.
* @target The device should set its operating frequency at
* freq or lowest-upper-than-freq value. If freq is
* higher than any operable frequency, set maximum.
@@ -61,11 +81,17 @@ 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.
+ *
+ * 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;
+ int qos_type;
+ struct devfreq_pm_qos_table *qos_list;
+
int (*target)(struct device *dev, unsigned long *freq);
int (*get_dev_status)(struct device *dev,
struct devfreq_dev_status *stat);
@@ -126,6 +152,10 @@ 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
+ * @qos_use_max true: throughput (larger is faster)
+ * false: latency (smaller is faster)
*
* This structure stores the devfreq information for a give device.
*
@@ -154,6 +184,9 @@ struct devfreq {
unsigned long min_freq;
unsigned long max_freq;
+ struct notifier_block qos_nb;
+ unsigned long qos_min_freq;
+ bool qos_use_max;
};
#if defined(CONFIG_PM_DEVFREQ)
--
1.7.4.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 RESEND] PM / devfreq: add PM QoS support
2012-02-29 9:43 ` [PATCH v2 RESEND] " MyungJoo Ham
@ 2012-02-29 22:19 ` Turquette, Mike
2012-03-04 22:30 ` Rafael J. Wysocki
0 siblings, 1 reply; 6+ messages in thread
From: Turquette, Mike @ 2012-02-29 22:19 UTC (permalink / raw
To: MyungJoo Ham
Cc: linux-kernel, linux-pm, Kyungmin Park, Rafael J. Wysocki,
Kevin Hilman, mark gross, myungjoo.ham, Jean Pihet
On Wed, Feb 29, 2012 at 1:43 AM, MyungJoo Ham <myungjoo.ham@samsung.com> wrote:
> + /* Check the sanity of qos_list/qos_type */
> + if (profile->qos_type || profile->qos_list) {
> + switch (profile->qos_type) {
> + case PM_QOS_CPU_DMA_LATENCY:
> + case PM_QOS_NETWORK_LATENCY:
> + devfreq->qos_use_max = false;
> + break;
> + case PM_QOS_NETWORK_THROUGHPUT:
> + devfreq->qos_use_max = true;
> + break;
Hello MyungJoo!
I see that you re-using the same old PM QoS handles in this
implementation. Do you feel this is the right way to do it? Your
example of using DMA for multimedia devices (given in the changelog)
has nothing to do with network throughput, yet that constraint-type is
used here.
I wonder if a better solution than overloading these classifications exist.
Just to toss around ideas, what about having per-device PM QoS
throughput constraints which are generalized (e.g., not tied to a
concept such as "network"). I've Cc'd Jean Pihet (yet again) who has
some good experience making PM QoS-type interfaces work on a
per-device basis.
I wonder, ultimately, if instead of feeding QoS constraints into
devfreq if a better design might be to have devfreq feed input into a
greater QoS framework. E.g:
A scalable bus used by many devices might have two different device
drivers that want to call pm_qos_device_tput(...), and also the
devfreq driver for that bus also calls pm_qos_device_tput(...). So
essentially there are three points in the code where inputs can be
driven into one common per-device QoS layer for the generic concept of
"device throughput". This way devfreq support is not a prerequisite
for scaling a device in a generic way, but a nice framework for
devices which can monitor their own activity level, built on top of a
per-device pm qos layer.
Thoughts?
Mike
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 RESEND] PM / devfreq: add PM QoS support
2012-02-29 22:19 ` Turquette, Mike
@ 2012-03-04 22:30 ` Rafael J. Wysocki
2012-03-05 1:09 ` MyungJoo Ham
0 siblings, 1 reply; 6+ messages in thread
From: Rafael J. Wysocki @ 2012-03-04 22:30 UTC (permalink / raw
To: Turquette, Mike
Cc: MyungJoo Ham, linux-kernel, linux-pm, Kyungmin Park, Kevin Hilman,
mark gross, myungjoo.ham, Jean Pihet
On Wednesday, February 29, 2012, Turquette, Mike wrote:
> On Wed, Feb 29, 2012 at 1:43 AM, MyungJoo Ham <myungjoo.ham@samsung.com> wrote:
> > + /* Check the sanity of qos_list/qos_type */
> > + if (profile->qos_type || profile->qos_list) {
> > + switch (profile->qos_type) {
> > + case PM_QOS_CPU_DMA_LATENCY:
> > + case PM_QOS_NETWORK_LATENCY:
> > + devfreq->qos_use_max = false;
> > + break;
> > + case PM_QOS_NETWORK_THROUGHPUT:
> > + devfreq->qos_use_max = true;
> > + break;
>
> Hello MyungJoo!
>
> I see that you re-using the same old PM QoS handles in this
> implementation. Do you feel this is the right way to do it? Your
> example of using DMA for multimedia devices (given in the changelog)
> has nothing to do with network throughput, yet that constraint-type is
> used here.
>
> I wonder if a better solution than overloading these classifications exist.
>
> Just to toss around ideas, what about having per-device PM QoS
> throughput constraints which are generalized (e.g., not tied to a
> concept such as "network"). I've Cc'd Jean Pihet (yet again) who has
> some good experience making PM QoS-type interfaces work on a
> per-device basis.
>
> I wonder, ultimately, if instead of feeding QoS constraints into
> devfreq if a better design might be to have devfreq feed input into a
> greater QoS framework. E.g:
>
> A scalable bus used by many devices might have two different device
> drivers that want to call pm_qos_device_tput(...), and also the
> devfreq driver for that bus also calls pm_qos_device_tput(...). So
> essentially there are three points in the code where inputs can be
> driven into one common per-device QoS layer for the generic concept of
> "device throughput". This way devfreq support is not a prerequisite
> for scaling a device in a generic way, but a nice framework for
> devices which can monitor their own activity level, built on top of a
> per-device pm qos layer.
>
> Thoughts?
I agree with the general idea, definitely would prefer it to what is
currently being proposed.
Thanks,
Rafael
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 RESEND] PM / devfreq: add PM QoS support
2012-03-04 22:30 ` Rafael J. Wysocki
@ 2012-03-05 1:09 ` MyungJoo Ham
0 siblings, 0 replies; 6+ messages in thread
From: MyungJoo Ham @ 2012-03-05 1:09 UTC (permalink / raw
To: Rafael J. Wysocki
Cc: Turquette, Mike, linux-kernel, linux-pm, Kyungmin Park,
Kevin Hilman, mark gross, Jean Pihet
On Mon, Mar 5, 2012 at 7:30 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Wednesday, February 29, 2012, Turquette, Mike wrote:
>> On Wed, Feb 29, 2012 at 1:43 AM, MyungJoo Ham <myungjoo.ham@samsung.com> wrote:
>> > + /* Check the sanity of qos_list/qos_type */
>> > + if (profile->qos_type || profile->qos_list) {
>> > + switch (profile->qos_type) {
>> > + case PM_QOS_CPU_DMA_LATENCY:
>> > + case PM_QOS_NETWORK_LATENCY:
>> > + devfreq->qos_use_max = false;
>> > + break;
>> > + case PM_QOS_NETWORK_THROUGHPUT:
>> > + devfreq->qos_use_max = true;
>> > + break;
>>
>> Hello MyungJoo!
>>
>> I see that you re-using the same old PM QoS handles in this
>> implementation. Do you feel this is the right way to do it? Your
>> example of using DMA for multimedia devices (given in the changelog)
>> has nothing to do with network throughput, yet that constraint-type is
>> used here.
>>
>> I wonder if a better solution than overloading these classifications exist.
>>
>> Just to toss around ideas, what about having per-device PM QoS
>> throughput constraints which are generalized (e.g., not tied to a
>> concept such as "network"). I've Cc'd Jean Pihet (yet again) who has
>> some good experience making PM QoS-type interfaces work on a
>> per-device basis.
>>
>> I wonder, ultimately, if instead of feeding QoS constraints into
>> devfreq if a better design might be to have devfreq feed input into a
>> greater QoS framework. E.g:
>>
>> A scalable bus used by many devices might have two different device
>> drivers that want to call pm_qos_device_tput(...), and also the
>> devfreq driver for that bus also calls pm_qos_device_tput(...). So
>> essentially there are three points in the code where inputs can be
>> driven into one common per-device QoS layer for the generic concept of
>> "device throughput". This way devfreq support is not a prerequisite
>> for scaling a device in a generic way, but a nice framework for
>> devices which can monitor their own activity level, built on top of a
>> per-device pm qos layer.
>>
>> Thoughts?
>
> I agree with the general idea, definitely would prefer it to what is
> currently being proposed.
Supporting per-device PM-QoS at devfreq is an option that I'm
considering as well as this global PM-QoS. I simply thought to
implement that after global Pm-QoS. (I'm intendeing to support both at
devfreq)
First of all, this is not going to be tied to DMA-BUS only as
currently we are implementing this on other types of devices as well
including GPU, Memory-interface, and others (IPs related with graphics
and/or multimedia); other manufactorers told that they are
implementing these. Although devfreq is now related with DMA_LATENCY
only, those NETWORK_* are added for the generality. And DMA_THROUGHPUT
and DVFS_LATENCY will be added as well if they are added to global
PM_QOS classes.
However, with BUS(w/ DMA) devfreq, the problem with using per-device
PM-QoS only at devfreq is that the devices that requests QoS on the
bus may be attached to different types of bus. The QoS value for bus
in Exynos4210 will be different from Exynos4412 or Exynos5410 while an
identical IP (or in-SoC device) can be attached to all the three chips
(which we are experiencing). When that IP requests QoS value to the
bus, we need a standardized value, not a value specific to an SoC. We
may ensure that the all Exynos bus drivers to use the same metrics if
the IP is only attached to SoCs of a single company. However, there
are IPs that are attached to multiple companies' SoCs; such as most
GPUs. (And GPUs often request QoS values to busses.)
Cheers!
MyungJoo.
--
MyungJoo Ham, Ph.D.
System S/W Lab, S/W Center, Samsung Electronics
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-03-05 1:09 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2012-02-10 7:19 [PATCH] PM / devfreq: add PM QoS support MyungJoo Ham
2012-02-28 5:46 ` [PATCH v2] " MyungJoo Ham
2012-02-29 9:43 ` [PATCH v2 RESEND] " MyungJoo Ham
2012-02-29 22:19 ` Turquette, Mike
2012-03-04 22:30 ` Rafael J. Wysocki
2012-03-05 1:09 ` MyungJoo Ham
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