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Message-ID: <32ca5cc0-b7e0-a798-629a-9012b20de1bd@gmail.com>
Date: Sat, 18 Jun 2022 22:57:59 +0900
From: Chanwoo Choi <cwchoi00@...il.com>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: MyungJoo Ham <myungjoo.ham@...sung.com>,
Kyungmin Park <kyungmin.park@...sung.com>,
Chanwoo Choi <cw00.choi@...sung.com>,
Sibi Sankar <sibis@...eaurora.org>,
Saravana Kannan <skannan@...eaurora.org>,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/4] PM / devfreq: Rework freq_table to be local to
devfreq struct
On 22. 6. 18. 04:38, Christian Marangi wrote:
> On Sat, Jun 18, 2022 at 04:33:19AM +0900, Chanwoo Choi wrote:
>> Hi,
>>
>> Thanks for the good catch.
>>
>>
>> I think that this patch fixes issue of commit 0ec09ac2cebe
>> ("PM / devfreq: Set the freq_table of devfreq device").
>>
>
> Should I add this to the Fixes list?
Replace fixes commit information with commit 0ec09ac2cebe.
I'd like you to make the patch separated from this series
and then send them to linux-stable mailling list tool
because I think this patch should be maintained by linux stable patches.
>
>> When some devfreq driver without using passive governor
>> faces on the all errors including PROBE_DEFER
>> after executing devfreq_add_device, this issue will happen.
>>
>> Also need to check the devfreq device driver using freq_table
>> which was allocated dynamically. In case of devfreq/drivers/exynos-bus.c
>> used the devfreq->profile->freq_table after devfreq_add_device.
>>
>> On 22. 6. 15. 08:09, Christian 'Ansuel' Marangi wrote:
>>> Currently we reference the freq_table to the profile defined one and we
>>> make changes on it. Devfreq never supported PROBE_DEFER before the cpu
>>> based scaling support to the passive governor and assumed that a devfreq
>>> device could only had error and be done with it.
>>> Now that a device can PROBE_DEFER a rework to the freq_table logic is
>>> required.
>>>
>>> If a device PROBE_DEFER on the GOV_START, the freq_table is already set
>>> in the device profile struct and its init is skipped. This is due to the
>>> fact that it's common for devs to declare this kind of struct static.
>>> This cause the devfreq logic to find a freq table declared (freq_table
>>> not NULL) with random data and poiting to the old addrs freed by devm.
>> > This problem CAN be solved by devs by clearing the freq_table in their
>>> profile struct on driver exit path but it should not be trusted and it
>>> looks to use a flawed logic.
>>>
>>> A better solution is to move the freq_table and max_state to the
>>> devfreq struct and never change the profile struct.
>>> This permit to correctly handle PROBE_DEFER since the devfreq struct is
>>> reallocated and contains new values.
>>> Also the profile struct should only be used to init the driver and should
>>> not be used by the devfreq to write the freq_table if it's not provided
>>> by the driver.
>>>
>>
>> If possible, could you explain the patch description more simply?
>> Maybe, just focus on the 'freq_table' issue by device managed functions (devs).
>>
>
> Sure!
Thanks.
>
>>
>>> Fixes: a03dacb0316f ("PM / devfreq: Add cpu based scaling support to passive governor")
>>> Signed-off-by: Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
>>> ---
>>> drivers/devfreq/devfreq.c | 71 ++++++++++++++----------------
>>> drivers/devfreq/governor_passive.c | 14 +++---
>>> include/linux/devfreq.h | 4 ++
>>> 3 files changed, 45 insertions(+), 44 deletions(-)
>>>
>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>> index 01474daf4548..2e2b3b414d67 100644
>>> --- a/drivers/devfreq/devfreq.c
>>> +++ b/drivers/devfreq/devfreq.c
>>> @@ -123,7 +123,7 @@ void devfreq_get_freq_range(struct devfreq *devfreq,
>>> unsigned long *min_freq,
>>> unsigned long *max_freq)
>>> {
>>> - unsigned long *freq_table = devfreq->profile->freq_table;
>>> + unsigned long *freq_table = devfreq->freq_table;
>>> s32 qos_min_freq, qos_max_freq;
>>>
>>> lockdep_assert_held(&devfreq->lock);
>>> @@ -133,11 +133,11 @@ void devfreq_get_freq_range(struct devfreq *devfreq,
>>> * The devfreq drivers can initialize this in either ascending or
>>> * descending order and devfreq core supports both.
>>> */
>>> - if (freq_table[0] < freq_table[devfreq->profile->max_state - 1]) {
>>> + if (freq_table[0] < freq_table[devfreq->max_state - 1]) {
>>> *min_freq = freq_table[0];
>>> - *max_freq = freq_table[devfreq->profile->max_state - 1];
>>> + *max_freq = freq_table[devfreq->max_state - 1];
>>> } else {
>>> - *min_freq = freq_table[devfreq->profile->max_state - 1];
>>> + *min_freq = freq_table[devfreq->max_state - 1];
>>> *max_freq = freq_table[0];
>>> }
>>>
>>> @@ -169,8 +169,8 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>>> {
>>> int lev;
>>>
>>> - for (lev = 0; lev < devfreq->profile->max_state; lev++)
>>> - if (freq == devfreq->profile->freq_table[lev])
>>> + for (lev = 0; lev < devfreq->max_state; lev++)
>>> + if (freq == devfreq->freq_table[lev])
>>> return lev;
>>>
>>> return -EINVAL;
>>> @@ -178,7 +178,6 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>>>
>>> static int set_freq_table(struct devfreq *devfreq)
>>> {
>>> - struct devfreq_dev_profile *profile = devfreq->profile;
>>> struct dev_pm_opp *opp;
>>> unsigned long freq;
>>> int i, count;
>>> @@ -188,25 +187,22 @@ static int set_freq_table(struct devfreq *devfreq)
>>> if (count <= 0)
>>> return -EINVAL;
>>>
>>> - profile->max_state = count;
>>> - profile->freq_table = devm_kcalloc(devfreq->dev.parent,
>>> - profile->max_state,
>>> - sizeof(*profile->freq_table),
>>> - GFP_KERNEL);
>>> - if (!profile->freq_table) {
>>> - profile->max_state = 0;
>>> + devfreq->max_state = count;
>>> + devfreq->freq_table = devm_kcalloc(devfreq->dev.parent,
>>> + devfreq->max_state,
>>> + sizeof(*devfreq->freq_table),
>>> + GFP_KERNEL);
>>> + if (!devfreq->freq_table)
>>> return -ENOMEM;
>>> - }
>>>
>>> - for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
>>> + for (i = 0, freq = 0; i < devfreq->max_state; i++, freq++) {
>>> opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
>>> if (IS_ERR(opp)) {
>>> - devm_kfree(devfreq->dev.parent, profile->freq_table);
>>> - profile->max_state = 0;
>>> + devm_kfree(devfreq->dev.parent, devfreq->freq_table);
>>> return PTR_ERR(opp);
>>> }
>>> dev_pm_opp_put(opp);
>>> - profile->freq_table[i] = freq;
>>> + devfreq->freq_table[i] = freq;
>>> }
>>>
>>> return 0;
>>> @@ -246,7 +242,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>>
>>> if (lev != prev_lev) {
>>> devfreq->stats.trans_table[
>>> - (prev_lev * devfreq->profile->max_state) + lev]++;
>>> + (prev_lev * devfreq->max_state) + lev]++;
>>> devfreq->stats.total_trans++;
>>> }
>>>
>>> @@ -835,6 +831,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>> if (err < 0)
>>> goto err_dev;
>>> mutex_lock(&devfreq->lock);
>>> + } else {
>>> + devfreq->freq_table = devfreq->profile->freq_table;
>>> + devfreq->max_state = devfreq->profile->max_state;
>>> }
>>>
>>> devfreq->scaling_min_freq = find_available_min_freq(devfreq);
>>> @@ -870,8 +869,8 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>>
>>> devfreq->stats.trans_table = devm_kzalloc(&devfreq->dev,
>>> array3_size(sizeof(unsigned int),
>>> - devfreq->profile->max_state,
>>> - devfreq->profile->max_state),
>>> + devfreq->max_state,
>>> + devfreq->max_state),
>>> GFP_KERNEL);
>>> if (!devfreq->stats.trans_table) {
>>> mutex_unlock(&devfreq->lock);
>>> @@ -880,7 +879,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>> }
>>>
>>> devfreq->stats.time_in_state = devm_kcalloc(&devfreq->dev,
>>> - devfreq->profile->max_state,
>>> + devfreq->max_state,
>>> sizeof(*devfreq->stats.time_in_state),
>>> GFP_KERNEL);
>>> if (!devfreq->stats.time_in_state) {
>>> @@ -1665,9 +1664,9 @@ static ssize_t available_frequencies_show(struct device *d,
>>>
>>> mutex_lock(&df->lock);
>>>
>>> - for (i = 0; i < df->profile->max_state; i++)
>>> + for (i = 0; i < df->max_state; i++)
>>> count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
>>> - "%lu ", df->profile->freq_table[i]);
>>> + "%lu ", df->freq_table[i]);
>>>
>>> mutex_unlock(&df->lock);
>>> /* Truncate the trailing space */
>>> @@ -1690,7 +1689,7 @@ static ssize_t trans_stat_show(struct device *dev,
>>>
>>> if (!df->profile)
>>> return -EINVAL;
>>> - max_state = df->profile->max_state;
>>> + max_state = df->max_state;
>>>
>>> if (max_state == 0)
>>> return sprintf(buf, "Not Supported.\n");
>>> @@ -1707,19 +1706,17 @@ static ssize_t trans_stat_show(struct device *dev,
>>> len += sprintf(buf + len, " :");
>>> for (i = 0; i < max_state; i++)
>>> len += sprintf(buf + len, "%10lu",
>>> - df->profile->freq_table[i]);
>>> + df->freq_table[i]);
>>>
>>> len += sprintf(buf + len, " time(ms)\n");
>>>
>>> for (i = 0; i < max_state; i++) {
>>> - if (df->profile->freq_table[i]
>>> - == df->previous_freq) {
>>> + if (df->freq_table[i] == df->previous_freq)
>>> len += sprintf(buf + len, "*");
>>> - } else {
>>> + else
>>> len += sprintf(buf + len, " ");
>>> - }
>>> - len += sprintf(buf + len, "%10lu:",
>>> - df->profile->freq_table[i]);
>>> +
>>> + len += sprintf(buf + len, "%10lu:", df->freq_table[i]);
>>> for (j = 0; j < max_state; j++)
>>> len += sprintf(buf + len, "%10u",
>>> df->stats.trans_table[(i * max_state) + j]);
>>> @@ -1743,7 +1740,7 @@ static ssize_t trans_stat_store(struct device *dev,
>>> if (!df->profile)
>>> return -EINVAL;
>>>
>>> - if (df->profile->max_state == 0)
>>> + if (df->max_state == 0)
>>> return count;
>>>
>>> err = kstrtoint(buf, 10, &value);
>>> @@ -1751,11 +1748,11 @@ static ssize_t trans_stat_store(struct device *dev,
>>> return -EINVAL;
>>>
>>> mutex_lock(&df->lock);
>>> - memset(df->stats.time_in_state, 0, (df->profile->max_state *
>>> + memset(df->stats.time_in_state, 0, (df->max_state *
>>> sizeof(*df->stats.time_in_state)));
>>> memset(df->stats.trans_table, 0, array3_size(sizeof(unsigned int),
>>> - df->profile->max_state,
>>> - df->profile->max_state));
>>> + df->max_state,
>>> + df->max_state));
>>> df->stats.total_trans = 0;
>>> df->stats.last_update = get_jiffies_64();
>>> mutex_unlock(&df->lock);
>>> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
>>> index dcc9dd518197..1810966fd61d 100644
>>> --- a/drivers/devfreq/governor_passive.c
>>> +++ b/drivers/devfreq/governor_passive.c
>>> @@ -145,18 +145,18 @@ static int get_target_freq_with_devfreq(struct devfreq *devfreq,
>>> goto out;
>>>
>>> /* Use interpolation if required opps is not available */
>>> - for (i = 0; i < parent_devfreq->profile->max_state; i++)
>>> - if (parent_devfreq->profile->freq_table[i] == *freq)
>>> + for (i = 0; i < parent_devfreq->max_state; i++)
>>> + if (parent_devfreq->freq_table[i] == *freq)
>>> break;
>>>
>>> - if (i == parent_devfreq->profile->max_state)
>>> + if (i == parent_devfreq->max_state)
>>> return -EINVAL;
>>>
>>> - if (i < devfreq->profile->max_state) {
>>> - child_freq = devfreq->profile->freq_table[i];
>>> + if (i < devfreq->max_state) {
>>> + child_freq = devfreq->freq_table[i];
>>> } else {
>>> - count = devfreq->profile->max_state;
>>> - child_freq = devfreq->profile->freq_table[count - 1];
>>> + count = devfreq->max_state;
>>> + child_freq = devfreq->freq_table[count - 1];
>>> }
>>>
>>> out:
>>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>>> index dc10bee75a72..770a7532655c 100644
>>> --- a/include/linux/devfreq.h
>>> +++ b/include/linux/devfreq.h
>>> @@ -185,6 +185,10 @@ struct devfreq {
>>> struct notifier_block nb;
>>> struct delayed_work work;
>>>
>>> + /* devfreq local freq_table */
This comment is not necessary. Please remove it.
>>> + unsigned long *freq_table;
>>> + unsigned int max_state;
And need to add the description of newly added variables
to 'struct devfreq' structure description.
>>> +
>>> unsigned long previous_freq;
>>> struct devfreq_dev_status last_status;
>>>
>>
>>
>> --
>> Best Regards,
>> Samsung Electronics
>> Chanwoo Choi
>
--
Best Regards,
Samsung Electronics
Chanwoo Choi
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