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: Thu, 22 Nov 2018 11:58:02 +0900 [thread overview]
Message-ID: <5BF61B3A.9050402@samsung.com> (raw)
In-Reply-To: <1542823301-23563-4-git-send-email-l.luba@partner.samsung.com>
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.
> + 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.
> + 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.
> + }
> +
> + 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.
> + 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.
> + 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.
> + if (ret)
> + return ret;
> + }
> +
> if (!devfreq->governor)
> return 0;
>
>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
next prev parent reply other threads:[~2018-11-22 2:58 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 [this message]
2018-11-22 11:00 ` Lukasz Luba
2018-11-22 23:54 ` Chanwoo Choi
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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