From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chanwoo Choi Subject: Re: [PATCH 3/6] devfreq: add support for suspend/resume of a devfreq device Date: Fri, 23 Nov 2018 08:54:06 +0900 Message-ID: <5BF7419E.90006@samsung.com> References: <1542823301-23563-1-git-send-email-l.luba@partner.samsung.com> <1542823301-23563-4-git-send-email-l.luba@partner.samsung.com> <5BF61B3A.9050402@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Return-path: In-reply-to: Sender: linux-kernel-owner@vger.kernel.org To: Lukasz Luba , 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 List-Id: linux-pm@vger.kernel.org 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 >>> Suggested-by: Chanwoo Choi >>> Signed-off-by: Lukasz Luba >>> --- >>> 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