Hi Lukasz,

I add the one more comment for devfreq_resume_device()

On 2018? 11? 23? 19:01, Lukasz Luba wrote:

Hi Chanwoo Choi,

On 11/23/18 12:54 AM, Chanwoo Choi wrote:

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Hi Lukasz,

I add one more comment about devfreq_resume_device().

On 2018? 11? 22? 20:00, Lukasz Luba wrote:

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On 11/22/18 3:58 AM, Chanwoo Choi wrote:

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On 2018? 11? 22? 03:01, Lukasz Luba wrote:

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The patch adds support for handling suspend/resume process.
It uses atomic variables to make sure no race condition
affects the process.

The patch draws on Tobias Jakobi's work posted ~2 years ago, who tried to
solve issue with devfreq device's frequency during suspend/resume.
During the discussion on LKML some corner cases and comments appeared
related to the design. This patch address them keeping in mind suggestions
from Chanwoo Choi.

Please remove the duplicate information about patch history.

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Suggested-by: Tobias Jakobi <redacted>
Suggested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Lukasz Luba <redacted>
---
   drivers/devfreq/devfreq.c | 45 +++++++++++++++++++++++++++++++++++++++------
   1 file changed, 39 insertions(+), 6 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index cf9c643..7e09de8 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c

@@ -872,14 +872,33 @@ EXPORT_SYMBOL(devm_devfreq_remove_device);
    */
   int devfreq_suspend_device(struct devfreq *devfreq)
   {
-	if (!devfreq)
-		return -EINVAL;
+        int ret;

Move 'ret' definition under 'if (devfreq->suspend_freq) {'
because 'ret' is used if suspend_freq isn't zero.

Not only there, 6 lines above 'ret' is used for
devfreq->governor->event_handler().

OK.

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+        unsigned long prev_freq;
+        u32 flags = 0;
+
+        if (!devfreq)
+                return -EINVAL;
+
+        if (devfreq->governor) {
+		ret = devfreq->governor->event_handler(devfreq,
+					DEVFREQ_GOV_SUSPEND, NULL);
+		if (ret)
+			return ret;
+	}
   
-	if (!devfreq->governor)
-		return 0;
+	if (devfreq->suspend_freq) {
+		if (atomic_inc_return(&devfreq->suspend_count) > 1)
+			return 0;
   
-	return devfreq->governor->event_handler(devfreq,
-				DEVFREQ_GOV_SUSPEND, NULL);
+		ret = devfreq_set_target(devfreq, devfreq->suspend_freq,
+					 &prev_freq, flags);

Remove the 'prev_freq' parameter.

OK

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+		if (ret)
+			return ret;
+
+		devfreq->resume_freq = prev_freq;

As I commented on patch2, if devfreq_set_taget save the current frequency
to 'devfreq->resume_freq', this line is not needed.

OK

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+	}
+
+        return 0;
   }
   EXPORT_SYMBOL(devfreq_suspend_device);
   

@@ -893,9 +912,23 @@ EXPORT_SYMBOL(devfreq_suspend_device);
    */
   int devfreq_resume_device(struct devfreq *devfreq)
   {
+        int ret;

Move 'ret' definition under 'if (devfreq->suspend_freq) {'
because 'ret' is used if suspend_freq isn't zero.

OK

If you change the devfreq_resume_device() according to my new comment,
please ignore it.

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+        unsigned long prev_freq;

Remove prev_freq variable which is not used on this function.
After calling devfreq_set_target, prev_freq is not used.

OK

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+        u32 flags = 0;
+
   	if (!devfreq)
   		return -EINVAL;
   
+	if (devfreq->suspend_freq) {

In devfreq_resume_device(), it should check the 'devfreq->resume_freq'
instead of 'devfreq->suspend_freq'.

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+		if (atomic_dec_return(&devfreq->suspend_count) >= 1)
+			return 0;
+
+		ret = devfreq_set_target(devfreq, devfreq->resume_freq,
+					 &prev_freq, flags);

Remove the 'prev_freq' parameter.

OK

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+		if (ret)
+			return ret;
+	}
+
   	if (!devfreq->governor)
   		return 0;

Please change the code as following because you uses the following type
in the devfreq_suspend_device(). If there is any special issue, please
keep the same format in order to improve the readability.

	if (devfreq->governor) {
		ret = devfreq->governor->event_handler(devfreq,
				DEVFREQ_GOV_RESUME, NULL);
		if (ret)
			return ret;
	}

OK, I will change the code to keep the same format.
Thank you for the review.

Regards,
Lukasz

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics