From: Chanwoo Choi <cw00.choi@samsung.com>
To: Lukasz Luba <l.luba@partner.samsung.com>,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pm@vger.kernel.org, devicetree@vger.kernel.org
Cc: tjakobi@math.uni-bielefeld.de, myungjoo.ham@samsung.com,
kyungmin.park@samsung.com, rjw@rjwysocki.net,
len.brown@intel.com, pavel@ucw.cz, gregkh@linuxfoundation.org,
keescook@chromium.org, anton@enomsg.org, ccross@android.com,
tony.luck@intel.com, robh+dt@kernel.org, mark.rutland@arm.com,
kgene@kernel.org, krzk@kernel.org, m.szyprowski@samsung.com,
b.zolnierkie@samsung.com
Subject: Re: [PATCH 3/6] devfreq: add support for suspend/resume of a devfreq device
Date: Fri, 23 Nov 2018 08:54:06 +0900 [thread overview]
Message-ID: <5BF7419E.90006@samsung.com> (raw)
In-Reply-To: <cce4f194-b574-a12c-e876-f11a6f245940@partner.samsung.com>
Hi Lukasz,
I add one more comment about devfreq_resume_device().
On 2018년 11월 22일 20:00, Lukasz Luba wrote:
>
>
> On 11/22/18 3:58 AM, Chanwoo Choi wrote:
>> On 2018년 11월 22일 03:01, Lukasz Luba wrote:
>>> 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.
>>
>>>
>>> Suggested-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>>> Suggested-by: Chanwoo Choi <cw00.choi@samsung.com>
>>> Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
>>> ---
>>> 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.
>>
>>> + 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
>>
>>> + 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
>>
>>
>>> + }
>>> +
>>> + 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.
>>
>>> + 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
>>
>>> + u32 flags = 0;
>>> +
>>> if (!devfreq)
>>> return -EINVAL;
>>>
>>> + if (devfreq->suspend_freq) {
>>> + 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
>>
>>> + 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;
}
>>>
>>>
>>
>>
>
> Regards,
> Lukasz Luba
>
>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
next prev parent reply other threads:[~2018-11-22 23:54 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20181121180156eucas1p225af7f4341a039264ff26f2a9ad9bb12@eucas1p2.samsung.com>
2018-11-21 18:01 ` [PATCH 0/6] devfreq: handle suspend/resume Lukasz Luba
[not found] ` <CGME20181121180201eucas1p1f1f96941c3d16a96722e65d5c21bfe80@eucas1p1.samsung.com>
2018-11-21 18:01 ` [PATCH 1/6] devfreq: add basic fileds supporting suspend functionality Lukasz Luba
2018-11-22 2:37 ` Chanwoo Choi
[not found] ` <CGME20181121180202eucas1p27d3aa58411abeae03181c38b91fc67de@eucas1p2.samsung.com>
2018-11-21 18:01 ` [PATCH 2/6] devfreq: refactor set_target frequency function Lukasz Luba
2018-11-22 2:52 ` Chanwoo Choi
2018-11-22 2:54 ` Chanwoo Choi
2018-11-22 10:40 ` Lukasz Luba
2018-11-22 23:45 ` Chanwoo Choi
2018-11-23 9:58 ` Lukasz Luba
[not found] ` <CGME20181121180204eucas1p1c5891d498aa59c0e10dd3ba4727a4382@eucas1p1.samsung.com>
2018-11-21 18:01 ` [PATCH 3/6] devfreq: add support for suspend/resume of a devfreq device Lukasz Luba
2018-11-22 2:58 ` Chanwoo Choi
2018-11-22 11:00 ` Lukasz Luba
2018-11-22 23:54 ` Chanwoo Choi [this message]
2018-11-23 10:01 ` Lukasz Luba
2018-11-26 0:19 ` Chanwoo Choi
2018-12-03 14:05 ` Lukasz Luba
[not found] ` <CGME20181121180205eucas1p1dc52369476400cd07058d232bd8dbcd7@eucas1p1.samsung.com>
2018-11-21 18:01 ` [PATCH 4/6] devfreq: add devfreq_suspend/resume() functions Lukasz Luba
2018-11-22 3:07 ` Chanwoo Choi
2018-11-22 11:02 ` Lukasz Luba
[not found] ` <CGME20181121180206eucas1p265865226e3938a28e842e8367233dc2e@eucas1p2.samsung.com>
2018-11-21 18:01 ` [PATCH 5/6] drivers: power: suspend: call devfreq suspend/resume Lukasz Luba
2018-11-22 3:08 ` Chanwoo Choi
[not found] ` <CGME20181121180208eucas1p11482a783ab1b1bceb8c9f6a1f50682c3@eucas1p1.samsung.com>
2018-11-21 18:01 ` [PATCH 6/6] arm: dts: exynos4: set opp-suspend for DMC and leftbus Lukasz Luba
2018-11-22 3:09 ` Chanwoo Choi
2018-11-22 11:04 ` Lukasz Luba
2018-11-22 17:24 ` [PATCH 0/6] devfreq: handle suspend/resume Tobias Jakobi
2018-11-22 17:44 ` Lukasz Luba
[not found] ` <CGME20181121180201eucas1p1f1f96941c3d16a96722e65d5c21bfe80@epcms1p8>
2018-11-26 8:14 ` [PATCH 1/6] devfreq: add basic fileds supporting suspend functionality MyungJoo Ham
2018-12-03 14:03 ` Lukasz Luba
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