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Date: Fri, 17 Jun 2022 21:38:06 +0200
From: Christian Marangi <ansuelsmth@...il.com>
To: Chanwoo Choi <cwchoi00@...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 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?
> 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!
>
> > 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 */
> > + unsigned long *freq_table;
> > + unsigned int max_state;
> > +
> > unsigned long previous_freq;
> > struct devfreq_dev_status last_status;
> >
>
>
> --
> Best Regards,
> Samsung Electronics
> Chanwoo Choi
--
Ansuel
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