On 3/18/21 5:03 PM, Dong Aisheng wrote:

Hi Chanwoo,

On Sat, Mar 13, 2021 at 2:45 PM Dong Aisheng [off-list ref] wrote:

quoted

On Sat, Mar 13, 2021 at 12:09 AM Chanwoo Choi [off-list ref] wrote:

quoted

On 21. 3. 12. 오후 7:57, Dong Aisheng wrote:

quoted

On Thu, Mar 11, 2021 at 2:54 PM Chanwoo Choi [off-list ref] wrote:

quoted

On 3/10/21 1:56 PM, Dong Aisheng wrote:

quoted

On Wed, Mar 10, 2021 at 11:08 AM Chanwoo Choi [off-list ref] wrote:

quoted

On 3/10/21 11:56 AM, Dong Aisheng wrote:

quoted

On Wed, Mar 10, 2021 at 12:12 AM Chanwoo Choi [off-list ref] wrote:

quoted

On 21. 3. 10. 오전 12:58, Chanwoo Choi wrote:

quoted

On 21. 3. 9. 오후 9:58, Dong Aisheng wrote:

quoted

The devfreq monitor depends on the device to provide load information
by .get_dev_status() to calculate the next target freq.

And this will cause changing governor to simple ondemand fail
if device can't support.

Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
   drivers/devfreq/devfreq.c                 | 10 +++++++---
   drivers/devfreq/governor.h                |  2 +-
   drivers/devfreq/governor_simpleondemand.c |  3 +--
   3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 7231fe6862a2..d1787b6c7d7c 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c

@@ -482,10 +482,13 @@ static void devfreq_monitor(struct work_struct

*work)
    * to be called from governor in response to DEVFREQ_GOV_START
    * event when device is added to devfreq framework.
    */
-void devfreq_monitor_start(struct devfreq *devfreq)
+int devfreq_monitor_start(struct devfreq *devfreq)
   {
       if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
-        return;
+        return 0;
+
+    if (!devfreq->profile->get_dev_status)
+        return -EINVAL;

Again, I think that get_dev_status is not used for all governors.
So that it cause the governor start fail. Don't check whether
.get_dev_status is NULL or not.

I'm not quite understand your point.
it is used by governor_simpleondemand.c and tegra_devfreq_governor.
get_target_freq -> devfreq_update_stats -> get_dev_status

The devfreq can add the new governor by anyone.
So these functions like devfreq_monitor_* have to support
the governors and also must support the governor to be added
in the future.

Yes, but devfreq_monitor_* is only used by polling mode, right?
The governor using it has to implement get_dev_status unless
there's an exception in the future.

Currently this patch wants to address the issue that user can switch
to ondemand governor (polling mode) by sysfs even devices does
not support it (no get_dev_status implemented).

As I commented, I'll fix this issue. If devfreq driver doesn't implement
the .get_dev_status, don't show it via available_governors. I think that
it is fundamental solution to fix this issue.

Sounds good

quoted

So on this version,
don't add the this conditional statement on this function

Almost all this patch did is adding a checking for get_dev_status.
So do you mean drop this patch?
I wonder it's still a necessary checking to explicitly tell devfreq monitor
users that get_dev_status is needed during governor startup.

I think that the it is enough to check .get_dev_status in
devfreq_update_stats. We have to check it on where it is used.

I think the drawback of only checking .get_dev_status in
devfreq_update_stats is:
1. devfreq will still register successfully and ondemand governor starts ok
2. ondemand governor will still be shown in sysfs which is something
you want to fix
3. devfreq will end up printing endless error messages in devfreq_monitor worker
    "dvfs failed with (%d) error" as the possible missing .get_dev_status

I think that devfreq_monitor_start have to handle only work instance.
This approach is too considering the deep check list.
I want to resolve this periodical error log with different solution.

Actually, we have to reject the registration of devfreq device
when calling devfreq_add_device instead of checking .get_dev_status
in devfreq_monitor_start().

quoted

So i wonder if you don't like changing the common devfreq_monitor_start in order
to make it look common for all governors, then we probably still need
to fix it in
ondemand governor in order to avoid the possible above issues.

static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
                                unsigned int event, void *data)
{
        switch (event) {
        case DEVFREQ_GOV_START:
                if (!devfreq->profile->get_dev_status)
                        return -EINVAL;

                return devfreq_monitor_start(devfreq);
...
}

How do you think?

Any feedback?

I'm waiting for your confirmation whether dropping this one,
then I can re-sent the series.

Regards
Aisheng

quoted

Regards
Aisheng

quoted

quoted

quoted

And on next version, please use the capital letter for first character
on patch title as following:

- PM / devfreq: Check get_dev_status before start monitor

Okay to me.
Thanks for the suggestion.

Regards
Aisheng

quoted

quoted

Regards
Aisheng

quoted

quoted

Without checking, device can switch to ondemand governor if it does not support.

Am i missed something?

Regards
Aisheng

quoted

quoted

quoted

       switch (devfreq->profile->timer) {
       case DEVFREQ_TIMER_DEFERRABLE:

@@ -495,12 +498,13 @@ void devfreq_monitor_start(struct devfreq *devfreq)
           INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
           break;
       default:
-        return;
+        return -EINVAL;
       }
       if (devfreq->profile->polling_ms)
           queue_delayed_work(devfreq_wq, &devfreq->work,
               msecs_to_jiffies(devfreq->profile->polling_ms));
+    return 0;
   }
   EXPORT_SYMBOL(devfreq_monitor_start);

diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
index 5cee3f64fe2b..31af6d072a10 100644
--- a/drivers/devfreq/governor.h
+++ b/drivers/devfreq/governor.h

@@ -75,7 +75,7 @@ struct devfreq_governor {
                   unsigned int event, void *data);
   };
-void devfreq_monitor_start(struct devfreq *devfreq);
+int devfreq_monitor_start(struct devfreq *devfreq);
   void devfreq_monitor_stop(struct devfreq *devfreq);
   void devfreq_monitor_suspend(struct devfreq *devfreq);
   void devfreq_monitor_resume(struct devfreq *devfreq);

diff --git a/drivers/devfreq/governor_simpleondemand.c

b/drivers/devfreq/governor_simpleondemand.c
index d57b82a2b570..ea287b57cbf3 100644

--- a/drivers/devfreq/governor_simpleondemand.c
+++ b/drivers/devfreq/governor_simpleondemand.c

@@ -89,8 +89,7 @@ static int devfreq_simple_ondemand_handler(struct

devfreq *devfreq,
   {
       switch (event) {
       case DEVFREQ_GOV_START:
-        devfreq_monitor_start(devfreq);
-        break;
+        return devfreq_monitor_start(devfreq);
       case DEVFREQ_GOV_STOP:
           devfreq_monitor_stop(devfreq);

Need to handle the all points of devfreq_monitor_start() usage.
please check the tegra30-devfreq.c for this update.

$ grep -rn "devfreq_monitor_start" drivers/
drivers/devfreq/governor_simpleondemand.c:92:
devfreq_monitor_start(devfreq);
drivers/devfreq/tegra30-devfreq.c:744:
devfreq_monitor_start(devfreq);
......

--
Best Regards,
Samsung Electronics
Chanwoo Choi

--
Best Regards,
Chanwoo Choi
Samsung Electronics

--
Best Regards,
Chanwoo Choi
Samsung Electronics

--
Best Regards,
Samsung Electronics
Chanwoo Choi

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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